SpringCloud配置刷新原理解析

我们知道在SpringCloud中，当配置变更时，我们通过访问http://xxxx/refresh，可以在不启动服务的情况下获取最新的配置，那么它是如何做到的呢，当我们更改数据库配置并刷新后，如何能获取最新的数据源对象呢？下面我们看SpringCloud如何做到的。

一、环境变化

1.1、关于ContextRefresher

　　当我们访问/refresh时，会被RefreshEndpoint类所处理。我们来看源代码：

				?

									/*

									 * Copyright 2013-2014 the original author or authors.

									 *

									 * Licensed under the Apache License, Version 2.0 (the "License");

									 * you may not use this file except in compliance with the License.

									 * You may obtain a copy of the License at

									 *

									 *  http://www.apache.org/licenses/LICENSE-2.0

									 *

									 * Unless required by applicable law or agreed to in writing, software

									 * distributed under the License is distributed on an "AS IS" BASIS,

									 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

									 * See the License for the specific language governing permissions and

									 * limitations under the License.

									 */

									package org.springframework.cloud.endpoint;

									import java.util.Arrays;

									import java.util.Collection;

									import java.util.Set;

									import org.springframework.boot.actuate.endpoint.AbstractEndpoint;

									import org.springframework.boot.context.properties.ConfigurationProperties;

									import org.springframework.cloud.context.refresh.ContextRefresher;

									import org.springframework.jmx.export.annotation.ManagedOperation;

									import org.springframework.jmx.export.annotation.ManagedResource;

									/**

									 * @author Dave Syer

									 * @author Venil Noronha

									 */

									@ConfigurationProperties(prefix = "endpoints.refresh", ignoreUnknownFields = false)

									@ManagedResource

									public class RefreshEndpoint extends AbstractEndpoint<Collection<String>> {

									 private ContextRefresher contextRefresher;

									 public RefreshEndpoint(ContextRefresher contextRefresher) {

									  super("refresh");

									  this.contextRefresher = contextRefresher;

									 }

									 @ManagedOperation

									 public String[] refresh() {

									  Set<String> keys = contextRefresher.refresh();

									  return keys.toArray(new String[keys.size()]);

									 }

									 @Override

									 public Collection<String> invoke() {

									  return Arrays.asList(refresh());

									 }

									}

　　通过源代码我们了解到：当访问refresh端点时，实际上执行的是ContextRefresher的refresh方法，那么我们继续追踪源代码，找到其refresh方法：

				?

									public synchronized Set<String> refresh() {

									  Map<String, Object> before = extract(

									    this.context.getEnvironment().getPropertySources());

									  addConfigFilesToEnvironment();

									  Set<String> keys = changes(before,

									    extract(this.context.getEnvironment().getPropertySources())).keySet();

									  this.context.publishEvent(new EnvironmentChangeEvent(context, keys));

									  this.scope.refreshAll();

									  return keys;

									 }

　　我们可以看到refresh方法做了如下几件事情：

　　1）获取刷新之前的所有PropertySource

　　2) 调用addConfigFilesToEnvironment方法获取最新的配置

　　3) 调用changes方法更新配置信息

　　4) 发布EnvironmentChangeEnvent事件

　　5）调用refreshScope的refreshAll方法刷新范围

　　我们重点关注一下2，3，4步骤

1.2、addConfigFilesToEnvironment方法

　　我们先来看看这个方法是怎么实现的：

				?

									/* for testing */ ConfigurableApplicationContext addConfigFilesToEnvironment() {

									  ConfigurableApplicationContext capture = null;

									  try {

									   StandardEnvironment environment = copyEnvironment(

									     this.context.getEnvironment());

									   SpringApplicationBuilder builder = new SpringApplicationBuilder(Empty.class)

									     .bannerMode(Mode.OFF).web(false).environment(environment);

									   // Just the listeners that affect the environment (e.g. excluding logging

									   // listener because it has side effects)

									   builder.application()

									     .setListeners(Arrays.asList(new BootstrapApplicationListener(),

									       new ConfigFileApplicationListener()));

									   capture = builder.run();

									   if (environment.getPropertySources().contains(REFRESH_ARGS_PROPERTY_SOURCE)) {

									    environment.getPropertySources().remove(REFRESH_ARGS_PROPERTY_SOURCE);

									   }

									   MutablePropertySources target = this.context.getEnvironment()

									     .getPropertySources();

									   String targetName = null;

									   for (PropertySource<?> source : environment.getPropertySources()) {

									    String name = source.getName();

									    if (target.contains(name)) {

									     targetName = name;

									    }

									    if (!this.standardSources.contains(name)) {

									     if (target.contains(name)) {

									      target.replace(name, source);

									     }

									     else {

									      if (targetName != null) {

									       target.addAfter(targetName, source);

									      }

									      else {

									       // targetName was null so we are at the start of the list

									       target.addFirst(source);

									       targetName = name;

									      }

									     }

									    }

									   }

									  }

									  finally {

									   ConfigurableApplicationContext closeable = capture;

									   while (closeable != null) {

									    try {

									     closeable.close();

									    }

									    catch (Exception e) {

									     // Ignore;

									    }

									    if (closeable.getParent() instanceof ConfigurableApplicationContext) {

									     closeable = (ConfigurableApplicationContext) closeable.getParent();

									    }

									    else {

									     break;

									    }

									   }

									  }

									  return capture;

									 }

　　1) 该方法首先拷贝当前的Environment

　　2) 通过SpringApplicationBuilder构建了一个简单的SpringBoot启动程序并启动

				?

									builder.application().setListeners(Arrays.asList(new BootstrapApplicationListener(),

									       new ConfigFileApplicationListener()));

　　这里面会添加两个监听器分别为：BootstrapApplicationListener与ConfigFileApplicationListener，通过先前的学习，我们知道BootstrapApplicationListener是引导程序的核心监听器，而ConfigFileApplicationListener也是非常重要的类：

				?

									/*

									 * Copyright 2012-2017 the original author or authors.

									 *

									 * Licensed under the Apache License, Version 2.0 (the "License");

									 * you may not use this file except in compliance with the License.

									 * You may obtain a copy of the License at

									 *

									 *  http://www.apache.org/licenses/LICENSE-2.0

									 *

									 * Unless required by applicable law or agreed to in writing, software

									 * distributed under the License is distributed on an "AS IS" BASIS,

									 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

									 * See the License for the specific language governing permissions and

									 * limitations under the License.

									 */

									package org.springframework.boot.context.config;

									import java.io.IOException;

									import java.util.ArrayList;

									import java.util.Arrays;

									import java.util.Collection;

									import java.util.Collections;

									import java.util.Iterator;

									import java.util.LinkedHashSet;

									import java.util.LinkedList;

									import java.util.List;

									import java.util.Queue;

									import java.util.Set;

									import org.apache.commons.logging.Log;

									import org.springframework.beans.BeansException;

									import org.springframework.beans.CachedIntrospectionResults;

									import org.springframework.beans.factory.config.BeanFactoryPostProcessor;

									import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;

									import org.springframework.boot.SpringApplication;

									import org.springframework.boot.bind.PropertiesConfigurationFactory;

									import org.springframework.boot.bind.PropertySourcesPropertyValues;

									import org.springframework.boot.bind.RelaxedDataBinder;

									import org.springframework.boot.bind.RelaxedPropertyResolver;

									import org.springframework.boot.context.event.ApplicationEnvironmentPreparedEvent;

									import org.springframework.boot.context.event.ApplicationPreparedEvent;

									import org.springframework.boot.env.EnumerableCompositePropertySource;

									import org.springframework.boot.env.EnvironmentPostProcessor;

									import org.springframework.boot.env.PropertySourcesLoader;

									import org.springframework.boot.logging.DeferredLog;

									import org.springframework.context.ApplicationEvent;

									import org.springframework.context.ConfigurableApplicationContext;

									import org.springframework.context.annotation.ConfigurationClassPostProcessor;

									import org.springframework.context.event.SmartApplicationListener;

									import org.springframework.core.Ordered;

									import org.springframework.core.annotation.AnnotationAwareOrderComparator;

									import org.springframework.core.convert.ConversionService;

									import org.springframework.core.convert.support.DefaultConversionService;

									import org.springframework.core.env.ConfigurableEnvironment;

									import org.springframework.core.env.EnumerablePropertySource;

									import org.springframework.core.env.MutablePropertySources;

									import org.springframework.core.env.PropertySource;

									import org.springframework.core.env.PropertySources;

									import org.springframework.core.io.DefaultResourceLoader;

									import org.springframework.core.io.Resource;

									import org.springframework.core.io.ResourceLoader;

									import org.springframework.core.io.support.SpringFactoriesLoader;

									import org.springframework.util.Assert;

									import org.springframework.util.ResourceUtils;

									import org.springframework.util.StringUtils;

									import org.springframework.validation.BindException;

									/**

									 * {@link EnvironmentPostProcessor} that configures the context environment by loading

									 * properties from well known file locations. By default properties will be loaded from

									 * 'application.properties' and/or 'application.yml' files in the following locations:

									 * <ul>

									 * <li>classpath:</li>

									 * <li>file:./</li>

									 * <li>classpath:config/</li>

									 * <li>file:./config/:</li>

									 * </ul>

									 * <p>

									 * Alternative search locations and names can be specified using

									 * {@link #setSearchLocations(String)} and {@link #setSearchNames(String)}.

									 * <p>

									 * Additional files will also be loaded based on active profiles. For example if a 'web'

									 * profile is active 'application-web.properties' and 'application-web.yml' will be

									 * considered.

									 * <p>

									 * The 'spring.config.name' property can be used to specify an alternative name to load

									 * and the 'spring.config.location' property can be used to specify alternative search

									 * locations or specific files.

									 * <p>

									 * Configuration properties are also bound to the {@link SpringApplication}. This makes it

									 * possible to set {@link SpringApplication} properties dynamically, like the sources

									 * ("spring.main.sources" - a CSV list) the flag to indicate a web environment

									 * ("spring.main.web_environment=true") or the flag to switch off the banner

									 * ("spring.main.show_banner=false").

									 *

									 * @author Dave Syer

									 * @author Phillip Webb

									 * @author Stephane Nicoll

									 * @author Andy Wilkinson

									 * @author Eddú Meléndez

									 */

									public class ConfigFileApplicationListener

									  implements EnvironmentPostProcessor, SmartApplicationListener, Ordered {

									 private static final String DEFAULT_PROPERTIES = "defaultProperties";

									 // Note the order is from least to most specific (last one wins)

									 private static final String DEFAULT_SEARCH_LOCATIONS = "classpath:/,classpath:/config/,file:./,file:./config/";

									 private static final String DEFAULT_NAMES = "application";

									 /**

									  * The "active profiles" property name.

									  */

									 public static final String ACTIVE_PROFILES_PROPERTY = "spring.profiles.active";

									 /**

									  * The "includes profiles" property name.

									  */

									 public static final String INCLUDE_PROFILES_PROPERTY = "spring.profiles.include";

									 /**

									  * The "config name" property name.

									  */

									 public static final String CONFIG_NAME_PROPERTY = "spring.config.name";

									 /**

									  * The "config location" property name.

									  */

									 public static final String CONFIG_LOCATION_PROPERTY = "spring.config.location";

									 /**

									  * The default order for the processor.

									  */

									 public static final int DEFAULT_ORDER = Ordered.HIGHEST_PRECEDENCE + 10;

									 /**

									  * Name of the application configuration {@link PropertySource}.

									  */

									 public static final String APPLICATION_CONFIGURATION_PROPERTY_SOURCE_NAME = "applicationConfigurationProperties";

									 private final DeferredLog logger = new DeferredLog();

									 private String searchLocations;

									 private String names;

									 private int order = DEFAULT_ORDER;

									 private final ConversionService conversionService = new DefaultConversionService();

									 @Override

									 public boolean supportsEventType(Class<? extends ApplicationEvent> eventType) {

									  return ApplicationEnvironmentPreparedEvent.class.isAssignableFrom(eventType)

									    || ApplicationPreparedEvent.class.isAssignableFrom(eventType);

									 }

									 @Override

									 public boolean supportsSourceType(Class<?> aClass) {

									  return true;

									 }

									 @Override

									 public void onApplicationEvent(ApplicationEvent event) {

									  if (event instanceof ApplicationEnvironmentPreparedEvent) {

									   onApplicationEnvironmentPreparedEvent(

									     (ApplicationEnvironmentPreparedEvent) event);

									  }

									  if (event instanceof ApplicationPreparedEvent) {

									   onApplicationPreparedEvent(event);

									  }

									 }

									 private void onApplicationEnvironmentPreparedEvent(

									   ApplicationEnvironmentPreparedEvent event) {

									  List<EnvironmentPostProcessor> postProcessors = loadPostProcessors();

									  postProcessors.add(this);

									  AnnotationAwareOrderComparator.sort(postProcessors);

									  for (EnvironmentPostProcessor postProcessor : postProcessors) {

									   postProcessor.postProcessEnvironment(event.getEnvironment(),

									     event.getSpringApplication());

									  }

									 }

									 List<EnvironmentPostProcessor> loadPostProcessors() {

									  return SpringFactoriesLoader.loadFactories(EnvironmentPostProcessor.class,

									    getClass().getClassLoader());

									 }

									 @Override

									 public void postProcessEnvironment(ConfigurableEnvironment environment,

									   SpringApplication application) {

									  addPropertySources(environment, application.getResourceLoader());

									  configureIgnoreBeanInfo(environment);

									  bindToSpringApplication(environment, application);

									 }

									 private void configureIgnoreBeanInfo(ConfigurableEnvironment environment) {

									  if (System.getProperty(

									    CachedIntrospectionResults.IGNORE_BEANINFO_PROPERTY_NAME) == null) {

									   RelaxedPropertyResolver resolver = new RelaxedPropertyResolver(environment,

									     "spring.beaninfo.");

									   Boolean ignore = resolver.getProperty("ignore", Boolean.class, Boolean.TRUE);

									   System.setProperty(CachedIntrospectionResults.IGNORE_BEANINFO_PROPERTY_NAME,

									     ignore.toString());

									  }

									 }

									 private void onApplicationPreparedEvent(ApplicationEvent event) {

									  this.logger.replayTo(ConfigFileApplicationListener.class);

									  addPostProcessors(((ApplicationPreparedEvent) event).getApplicationContext());

									 }

									 /**

									  * Add config file property sources to the specified environment.

									  * @param environment the environment to add source to

									  * @param resourceLoader the resource loader

									  * @see #addPostProcessors(ConfigurableApplicationContext)

									  */

									 protected void addPropertySources(ConfigurableEnvironment environment,

									   ResourceLoader resourceLoader) {

									  RandomValuePropertySource.addToEnvironment(environment);

									  new Loader(environment, resourceLoader).load();

									 }

									 /**

									  * Bind the environment to the {@link SpringApplication}.

									  * @param environment the environment to bind

									  * @param application the application to bind to

									  */

									 protected void bindToSpringApplication(ConfigurableEnvironment environment,

									   SpringApplication application) {

									  PropertiesConfigurationFactory<SpringApplication> binder = new PropertiesConfigurationFactory<SpringApplication>(

									    application);

									  binder.setTargetName("spring.main");

									  binder.setConversionService(this.conversionService);

									  binder.setPropertySources(environment.getPropertySources());

									  try {

									   binder.bindPropertiesToTarget();

									  }

									  catch (BindException ex) {

									   throw new IllegalStateException("Cannot bind to SpringApplication", ex);

									  }

									 }

									 /**

									  * Add appropriate post-processors to post-configure the property-sources.

									  * @param context the context to configure

									  */

									 protected void addPostProcessors(ConfigurableApplicationContext context) {

									  context.addBeanFactoryPostProcessor(

									    new PropertySourceOrderingPostProcessor(context));

									 }

									 public void setOrder(int order) {

									  this.order = order;

									 }

									 @Override

									 public int getOrder() {

									  return this.order;

									 }

									 /**

									  * Set the search locations that will be considered as a comma-separated list. Each

									  * search location should be a directory path (ending in "/") and it will be prefixed

									  * by the file names constructed from {@link #setSearchNames(String) search names} and

									  * profiles (if any) plus file extensions supported by the properties loaders.

									  * Locations are considered in the order specified, with later items taking precedence

									  * (like a map merge).

									  * @param locations the search locations

									  */

									 public void setSearchLocations(String locations) {

									  Assert.hasLength(locations, "Locations must not be empty");

									  this.searchLocations = locations;

									 }

									 /**

									  * Sets the names of the files that should be loaded (excluding file extension) as a

									  * comma-separated list.

									  * @param names the names to load

									  */

									 public void setSearchNames(String names) {

									  Assert.hasLength(names, "Names must not be empty");

									  this.names = names;

									 }

									 /**

									  * {@link BeanFactoryPostProcessor} to re-order our property sources below any

									  * {@code @PropertySource} items added by the {@link ConfigurationClassPostProcessor}.

									  */

									 private class PropertySourceOrderingPostProcessor

									   implements BeanFactoryPostProcessor, Ordered {

									  private ConfigurableApplicationContext context;

									  PropertySourceOrderingPostProcessor(ConfigurableApplicationContext context) {

									   this.context = context;

									  }

									  @Override

									  public int getOrder() {

									   return Ordered.HIGHEST_PRECEDENCE;

									  }

									  @Override

									  public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory)

									    throws BeansException {

									   reorderSources(this.context.getEnvironment());

									  }

									  private void reorderSources(ConfigurableEnvironment environment) {

									   ConfigurationPropertySources

									     .finishAndRelocate(environment.getPropertySources());

									   PropertySource<?> defaultProperties = environment.getPropertySources()

									     .remove(DEFAULT_PROPERTIES);

									   if (defaultProperties != null) {

									    environment.getPropertySources().addLast(defaultProperties);

									   }

									  }

									 }

									 /**

									  * Loads candidate property sources and configures the active profiles.

									  */

									 private class Loader {

									  private final Log logger = ConfigFileApplicationListener.this.logger;

									  private final ConfigurableEnvironment environment;

									  private final ResourceLoader resourceLoader;

									  private PropertySourcesLoader propertiesLoader;

									  private Queue<Profile> profiles;

									  private List<Profile> processedProfiles;

									  private boolean activatedProfiles;

									  Loader(ConfigurableEnvironment environment, ResourceLoader resourceLoader) {

									   this.environment = environment;

									   this.resourceLoader = resourceLoader == null ? new DefaultResourceLoader()

									     : resourceLoader;

									  }

									  public void load() {

									   this.propertiesLoader = new PropertySourcesLoader();

									   this.activatedProfiles = false;

									   this.profiles = Collections.asLifoQueue(new LinkedList<Profile>());

									   this.processedProfiles = new LinkedList<Profile>();

									   // Pre-existing active profiles set via Environment.setActiveProfiles()

									   // are additional profiles and config files are allowed to add more if

									   // they want to, so don't call addActiveProfiles() here.

									   Set<Profile> initialActiveProfiles = initializeActiveProfiles();

									   this.profiles.addAll(getUnprocessedActiveProfiles(initialActiveProfiles));

									   if (this.profiles.isEmpty()) {

									    for (String defaultProfileName : this.environment.getDefaultProfiles()) {

									     Profile defaultProfile = new Profile(defaultProfileName, true);

									     if (!this.profiles.contains(defaultProfile)) {

									      this.profiles.add(defaultProfile);

									     }

									    }

									   }

									   // The default profile for these purposes is represented as null. We add it

									   // last so that it is first out of the queue (active profiles will then

									   // override any settings in the defaults when the list is reversed later).

									   this.profiles.add(null);

									   while (!this.profiles.isEmpty()) {

									    Profile profile = this.profiles.poll();

									    for (String location : getSearchLocations()) {

									     if (!location.endsWith("/")) {

									      // location is a filename already, so don't search for more

									      // filenames

									      load(location, null, profile);

									     }

									     else {

									      for (String name : getSearchNames()) {

									       load(location, name, profile);

									      }

									     }

									    }

									    this.processedProfiles.add(profile);

									   }

									   addConfigurationProperties(this.propertiesLoader.getPropertySources());

									  }

									  private Set<Profile> initializeActiveProfiles() {

									   if (!this.environment.containsProperty(ACTIVE_PROFILES_PROPERTY)

									     && !this.environment.containsProperty(INCLUDE_PROFILES_PROPERTY)) {

									    return Collections.emptySet();

									   }

									   // Any pre-existing active profiles set via property sources (e.g. System

									   // properties) take precedence over those added in config files.

									   SpringProfiles springProfiles = bindSpringProfiles(

									     this.environment.getPropertySources());

									   Set<Profile> activeProfiles = new LinkedHashSet<Profile>(

									     springProfiles.getActiveProfiles());

									   activeProfiles.addAll(springProfiles.getIncludeProfiles());

									   maybeActivateProfiles(activeProfiles);

									   return activeProfiles;

									  }

									  /**

									   * Return the active profiles that have not been processed yet. If a profile is

									   * enabled via both {@link #ACTIVE_PROFILES_PROPERTY} and

									   * {@link ConfigurableEnvironment#addActiveProfile(String)} it needs to be

									   * filtered so that the {@link #ACTIVE_PROFILES_PROPERTY} value takes precedence.

									   * <p>

									   * Concretely, if the "cloud" profile is enabled via the environment, it will take

									   * less precedence that any profile set via the {@link #ACTIVE_PROFILES_PROPERTY}.

									   * @param initialActiveProfiles the profiles that have been enabled via

									   * {@link #ACTIVE_PROFILES_PROPERTY}

									   * @return the unprocessed active profiles from the environment to enable

									   */

									  private List<Profile> getUnprocessedActiveProfiles(

									    Set<Profile> initialActiveProfiles) {

									   List<Profile> unprocessedActiveProfiles = new ArrayList<Profile>();

									   for (String profileName : this.environment.getActiveProfiles()) {

									    Profile profile = new Profile(profileName);

									    if (!initialActiveProfiles.contains(profile)) {

									     unprocessedActiveProfiles.add(profile);

									    }

									   }

									   // Reverse them so the order is the same as from getProfilesForValue()

									   // (last one wins when properties are eventually resolved)

									   Collections.reverse(unprocessedActiveProfiles);

									   return unprocessedActiveProfiles;

									  }

									  private void load(String location, String name, Profile profile) {

									   String group = "profile=" + (profile == null ? "" : profile);

									   if (!StringUtils.hasText(name)) {

									    // Try to load directly from the location

									    loadIntoGroup(group, location, profile);

									   }

									   else {

									    // Search for a file with the given name

									    for (String ext : this.propertiesLoader.getAllFileExtensions()) {

									     if (profile != null) {

									      // Try the profile-specific file

									      loadIntoGroup(group, location + name + "-" + profile + "." + ext,

									        null);

									      for (Profile processedProfile : this.processedProfiles) {

									       if (processedProfile != null) {

									        loadIntoGroup(group, location + name + "-"

									          + processedProfile + "." + ext, profile);

									       }

									      }

									      // Sometimes people put "spring.profiles: dev" in

									      // application-dev.yml (gh-340). Arguably we should try and error

									      // out on that, but we can be kind and load it anyway.

									      loadIntoGroup(group, location + name + "-" + profile + "." + ext,

									        profile);

									     }

									     // Also try the profile-specific section (if any) of the normal file

									     loadIntoGroup(group, location + name + "." + ext, profile);

									    }

									   }

									  }

									  private PropertySource<?> loadIntoGroup(String identifier, String location,

									    Profile profile) {

									   try {

									    return doLoadIntoGroup(identifier, location, profile);

									   }

									   catch (Exception ex) {

									    throw new IllegalStateException(

									      "Failed to load property source from location '" + location + "'",

									      ex);

									   }

									  }

									  private PropertySource<?> doLoadIntoGroup(String identifier, String location,

									    Profile profile) throws IOException {

									   Resource resource = this.resourceLoader.getResource(location);

									   PropertySource<?> propertySource = null;

									   StringBuilder msg = new StringBuilder();

									   if (resource != null && resource.exists()) {

									    String name = "applicationConfig: [" + location + "]";

									    String group = "applicationConfig: [" + identifier + "]";

									    propertySource = this.propertiesLoader.load(resource, group, name,

									      (profile == null ? null : profile.getName()));

									    if (propertySource != null) {

									     msg.append("Loaded ");

									     handleProfileProperties(propertySource);

									    }

									    else {

									     msg.append("Skipped (empty) ");

									    }

									   }

									   else {

									    msg.append("Skipped ");

									   }

									   msg.append("config file ");

									   msg.append(getResourceDescription(location, resource));

									   if (profile != null) {

									    msg.append(" for profile ").append(profile);

									   }

									   if (resource == null || !resource.exists()) {

									    msg.append(" resource not found");

									    this.logger.trace(msg);

									   }

									   else {

									    this.logger.debug(msg);

									   }

									   return propertySource;

									  }

									  private String getResourceDescription(String location, Resource resource) {

									   String resourceDescription = "'" + location + "'";

									   if (resource != null) {

									    try {

									     resourceDescription = String.format("'%s' (%s)",

									       resource.getURI().toASCIIString(), location);

									    }

									    catch (IOException ex) {

									     // Use the location as the description

									    }

									   }

									   return resourceDescription;

									  }

									  private void handleProfileProperties(PropertySource<?> propertySource) {

									   SpringProfiles springProfiles = bindSpringProfiles(propertySource);

									   maybeActivateProfiles(springProfiles.getActiveProfiles());

									   addProfiles(springProfiles.getIncludeProfiles());

									  }

									  private SpringProfiles bindSpringProfiles(PropertySource<?> propertySource) {

									   MutablePropertySources propertySources = new MutablePropertySources();

									   propertySources.addFirst(propertySource);

									   return bindSpringProfiles(propertySources);

									  }

									  private SpringProfiles bindSpringProfiles(PropertySources propertySources) {

									   SpringProfiles springProfiles = new SpringProfiles();

									   RelaxedDataBinder dataBinder = new RelaxedDataBinder(springProfiles,

									     "spring.profiles");

									   dataBinder.bind(new PropertySourcesPropertyValues(propertySources, false));

									   springProfiles.setActive(resolvePlaceholders(springProfiles.getActive()));

									   springProfiles.setInclude(resolvePlaceholders(springProfiles.getInclude()));

									   return springProfiles;

									  }

									  private List<String> resolvePlaceholders(List<String> values) {

									   List<String> resolved = new ArrayList<String>();

									   for (String value : values) {

									    resolved.add(this.environment.resolvePlaceholders(value));

									   }

									   return resolved;

									  }

									  private void maybeActivateProfiles(Set<Profile> profiles) {

									   if (this.activatedProfiles) {

									    if (!profiles.isEmpty()) {

									     this.logger.debug("Profiles already activated, '" + profiles

									       + "' will not be applied");

									    }

									    return;

									   }

									   if (!profiles.isEmpty()) {

									    addProfiles(profiles);

									    this.logger.debug("Activated profiles "

									      + StringUtils.collectionToCommaDelimitedString(profiles));

									    this.activatedProfiles = true;

									    removeUnprocessedDefaultProfiles();

									   }

									  }

									  private void removeUnprocessedDefaultProfiles() {

									   for (Iterator<Profile> iterator = this.profiles.iterator(); iterator

									     .hasNext();) {

									    if (iterator.next().isDefaultProfile()) {

									     iterator.remove();

									    }

									   }

									  }

									  private void addProfiles(Set<Profile> profiles) {

									   for (Profile profile : profiles) {

									    this.profiles.add(profile);

									    if (!environmentHasActiveProfile(profile.getName())) {

									     // If it's already accepted we assume the order was set

									     // intentionally

									     prependProfile(this.environment, profile);

									    }

									   }

									  }

									  private boolean environmentHasActiveProfile(String profile) {

									   for (String activeProfile : this.environment.getActiveProfiles()) {

									    if (activeProfile.equals(profile)) {

									     return true;

									    }

									   }

									   return false;

									  }

									  private void prependProfile(ConfigurableEnvironment environment,

									    Profile profile) {

									   Set<String> profiles = new LinkedHashSet<String>();

									   environment.getActiveProfiles(); // ensure they are initialized

									   // But this one should go first (last wins in a property key clash)

									   profiles.add(profile.getName());

									   profiles.addAll(Arrays.asList(environment.getActiveProfiles()));

									   environment.setActiveProfiles(profiles.toArray(new String[profiles.size()]));

									  }

									  private Set<String> getSearchLocations() {

									   Set<String> locations = new LinkedHashSet<String>();

									   // User-configured settings take precedence, so we do them first

									   if (this.environment.containsProperty(CONFIG_LOCATION_PROPERTY)) {

									    for (String path : asResolvedSet(

									      this.environment.getProperty(CONFIG_LOCATION_PROPERTY), null)) {

									     if (!path.contains("$")) {

									      path = StringUtils.cleanPath(path);

									      if (!ResourceUtils.isUrl(path)) {

									       path = ResourceUtils.FILE_URL_PREFIX + path;

									      }

									     }

									     locations.add(path);

									    }

									   }

									   locations.addAll(

									     asResolvedSet(ConfigFileApplicationListener.this.searchLocations,

									       DEFAULT_SEARCH_LOCATIONS));

									   return locations;

									  }

									  private Set<String> getSearchNames() {

									   if (this.environment.containsProperty(CONFIG_NAME_PROPERTY)) {

									    return asResolvedSet(this.environment.getProperty(CONFIG_NAME_PROPERTY),

									      null);

									   }

									   return asResolvedSet(ConfigFileApplicationListener.this.names, DEFAULT_NAMES);

									  }

									  private Set<String> asResolvedSet(String value, String fallback) {

									   List<String> list = Arrays.asList(StringUtils.trimArrayElements(

									     StringUtils.commaDelimitedListToStringArray(value != null

									       ? this.environment.resolvePlaceholders(value) : fallback)));

									   Collections.reverse(list);

									   return new LinkedHashSet<String>(list);

									  }

									  private void addConfigurationProperties(MutablePropertySources sources) {

									   List<PropertySource<?>> reorderedSources = new ArrayList<PropertySource<?>>();

									   for (PropertySource<?> item : sources) {

									    reorderedSources.add(item);

									   }

									   addConfigurationProperties(

									     new ConfigurationPropertySources(reorderedSources));

									  }

									  private void addConfigurationProperties(

									    ConfigurationPropertySources configurationSources) {

									   MutablePropertySources existingSources = this.environment

									     .getPropertySources();

									   if (existingSources.contains(DEFAULT_PROPERTIES)) {

									    existingSources.addBefore(DEFAULT_PROPERTIES, configurationSources);

									   }

									   else {

									    existingSources.addLast(configurationSources);

									   }

									  }

									 }

									 private static class Profile {

									  private final String name;

									  private final boolean defaultProfile;

									  Profile(String name) {

									   this(name, false);

									  }

									  Profile(String name, boolean defaultProfile) {

									   Assert.notNull(name, "Name must not be null");

									   this.name = name;

									   this.defaultProfile = defaultProfile;

									  }

									  public String getName() {

									   return this.name;

									  }

									  public boolean isDefaultProfile() {

									   return this.defaultProfile;

									  }

									  @Override

									  public String toString() {

									   return this.name;

									  }

									  @Override

									  public int hashCode() {

									   return this.name.hashCode();

									  }

									  @Override

									  public boolean equals(Object obj) {

									   if (obj == this) {

									    return true;

									   }

									   if (obj == null || obj.getClass() != getClass()) {

									    return false;

									   }

									   return ((Profile) obj).name.equals(this.name);

									  }

									 }

									 /**

									  * Holds the configuration {@link PropertySource}s as they are loaded can relocate

									  * them once configuration classes have been processed.

									  */

									 static class ConfigurationPropertySources

									   extends EnumerablePropertySource<Collection<PropertySource<?>>> {

									  private final Collection<PropertySource<?>> sources;

									  private final String[] names;

									  ConfigurationPropertySources(Collection<PropertySource<?>> sources) {

									   super(APPLICATION_CONFIGURATION_PROPERTY_SOURCE_NAME, sources);

									   this.sources = sources;

									   List<String> names = new ArrayList<String>();

									   for (PropertySource<?> source : sources) {

									    if (source instanceof EnumerablePropertySource) {

									     names.addAll(Arrays.asList(

									       ((EnumerablePropertySource<?>) source).getPropertyNames()));

									    }

									   }

									   this.names = names.toArray(new String[names.size()]);

									  }

									  @Override

									  public Object getProperty(String name) {

									   for (PropertySource<?> propertySource : this.sources) {

									    Object value = propertySource.getProperty(name);

									    if (value != null) {

									     return value;

									    }

									   }

									   return null;

									  }

									  public static void finishAndRelocate(MutablePropertySources propertySources) {

									   String name = APPLICATION_CONFIGURATION_PROPERTY_SOURCE_NAME;

									   ConfigurationPropertySources removed = (ConfigurationPropertySources) propertySources

									     .get(name);

									   if (removed != null) {

									    for (PropertySource<?> propertySource : removed.sources) {

									     if (propertySource instanceof EnumerableCompositePropertySource) {

									      EnumerableCompositePropertySource composite = (EnumerableCompositePropertySource) propertySource;

									      for (PropertySource<?> nested : composite.getSource()) {

									       propertySources.addAfter(name, nested);

									       name = nested.getName();

									      }

									     }

									     else {

									      propertySources.addAfter(name, propertySource);

									     }

									    }

									    propertySources.remove(APPLICATION_CONFIGURATION_PROPERTY_SOURCE_NAME);

									   }

									  }

									  @Override

									  public String[] getPropertyNames() {

									   return this.names;

									  }

									 }

									 /**

									  * Holder for {@code spring.profiles} properties.

									  */

									 static final class SpringProfiles {

									  private List<String> active = new ArrayList<String>();

									  private List<String> include = new ArrayList<String>();

									  public List<String> getActive() {

									   return this.active;

									  }

									  public void setActive(List<String> active) {

									   this.active = active;

									  }

									  public List<String> getInclude() {

									   return this.include;

									  }

									  public void setInclude(List<String> include) {

									   this.include = include;

									  }

									  Set<Profile> getActiveProfiles() {

									   return asProfileSet(this.active);

									  }

									  Set<Profile> getIncludeProfiles() {

									   return asProfileSet(this.include);

									  }

									  private Set<Profile> asProfileSet(List<String> profileNames) {

									   List<Profile> profiles = new ArrayList<Profile>();

									   for (String profileName : profileNames) {

									    profiles.add(new Profile(profileName));

									   }

									   Collections.reverse(profiles);

									   return new LinkedHashSet<Profile>(profiles);

									  }

									 }

									}

　　根据javadoc注释的说明，这个类会从指定的位置加载application.properties或者application.yml并将它们的属性读到Envrionment当中，其中这几个方法大家关注下：

				?

									@Override

									public void onApplicationEvent(ApplicationEvent event) {

									 if (event instanceof ApplicationEnvironmentPreparedEvent) {

									  onApplicationEnvironmentPreparedEvent(

									    (ApplicationEnvironmentPreparedEvent) event);

									 }

									 if (event instanceof ApplicationPreparedEvent) {

									  onApplicationPreparedEvent(event);

									 }

									}

　　当springboot程序启动时一定会触发该事件监听，如果当前是 ApplicationEnvironmentPreparedEvent事件就会调用 onApplicationEnvironmentPreparedEvent方法，最终该方法会执行：

				?

									@Override

									public void postProcessEnvironment(ConfigurableEnvironment environment,

									  SpringApplication application) {

									 addPropertySources(environment, application.getResourceLoader());

									 configureIgnoreBeanInfo(environment);

									 bindToSpringApplication(environment, application);

									}

　其中 bindToSpringApplication方法为：

				?

									/**

									  * Bind the environment to the {@link SpringApplication}.

									  * @param environment the environment to bind

									  * @param application the application to bind to

									  */

									 protected void bindToSpringApplication(ConfigurableEnvironment environment,

									   SpringApplication application) {

									  PropertiesConfigurationFactory<SpringApplication> binder = new PropertiesConfigurationFactory<SpringApplication>(

									    application);

									  binder.setTargetName("spring.main");

									  binder.setConversionService(this.conversionService);

									  binder.setPropertySources(environment.getPropertySources());

									  try {

									   binder.bindPropertiesToTarget();

									  }

									  catch (BindException ex) {

									   throw new IllegalStateException("Cannot bind to SpringApplication", ex);

									  }

									 }

　　很明显该方法是将Environment绑定到对应SpringApplication上，通过这个类就可以获取到我们更改过后的配置了

1.3、changes方法

				?

									private Map<String, Object> changes(Map<String, Object> before,

									   Map<String, Object> after) {

									  Map<String, Object> result = new HashMap<String, Object>();

									  for (String key : before.keySet()) {

									   if (!after.containsKey(key)) {

									    result.put(key, null);

									   }

									   else if (!equal(before.get(key), after.get(key))) {

									    result.put(key, after.get(key));

									   }

									  }

									  for (String key : after.keySet()) {

									   if (!before.containsKey(key)) {

									    result.put(key, after.get(key));

									   }

									  }

									  return result;

									 }

　　changes方法其实就是处理配置变更信息的，分以下几种情况：

　　1）如果刷新过后配置文件新增配置就添加到Map里

　　2) 如果有配置变更就添加变更后的配置

　　3) 如果删除了原先的配置，就把原先的key对应的值设置为null

　　至此经过changes方法后，上下文环境已经拥有最新的配置了。

1.4、发布事件

　　当上述步骤都执行完毕后，紧接着会发布EnvrionmentChangeEvent事件，可是这个事件谁来监听呢？在这里我贴出官网的一段描述：

　　　应用程序将收听EnvironmentChangeEvent，并以几种标准方式进行更改（用户可以以常规方式添加ApplicationListeners附加ApplicationListeners）。当观察到EnvironmentChangeEvent时，它将有一个已更改的键值列表，应用程序将使用以下内容：

1.重新绑定上下文中的任何@ConfigurationProperties bean

2.为logging.level.*中的任何属性设置记录器级别

　　根据官网描述我们知道将变更一下操作行为@ConfigurationProperties的bean与更改日志level，那么如何做到的呢？结合官网文档我们来关注以下两个类：

　　ConfigurationPropertiesRebinder:

				?

									/*

									 * Copyright 2013-2014 the original author or authors.

									 *

									 * Licensed under the Apache License, Version 2.0 (the "License");

									 * you may not use this file except in compliance with the License.

									 * You may obtain a copy of the License at

									 *

									 *  http://www.apache.org/licenses/LICENSE-2.0

									 *

									 * Unless required by applicable law or agreed to in writing, software

									 * distributed under the License is distributed on an "AS IS" BASIS,

									 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

									 * See the License for the specific language governing permissions and

									 * limitations under the License.

									 */

									package org.springframework.cloud.context.properties;

									import java.util.HashSet;

									import java.util.Map;

									import java.util.Set;

									import java.util.concurrent.ConcurrentHashMap;

									import org.springframework.aop.framework.Advised;

									import org.springframework.aop.support.AopUtils;

									import org.springframework.beans.BeansException;

									import org.springframework.boot.context.properties.ConfigurationProperties;

									import org.springframework.cloud.context.config.annotation.RefreshScope;

									import org.springframework.cloud.context.environment.EnvironmentChangeEvent;

									import org.springframework.context.ApplicationContext;

									import org.springframework.context.ApplicationContextAware;

									import org.springframework.context.ApplicationListener;

									import org.springframework.core.env.Environment;

									import org.springframework.jmx.export.annotation.ManagedAttribute;

									import org.springframework.jmx.export.annotation.ManagedOperation;

									import org.springframework.jmx.export.annotation.ManagedResource;

									import org.springframework.stereotype.Component;

									/**

									 * Listens for {@link EnvironmentChangeEvent} and rebinds beans that were bound to the

									 * {@link Environment} using {@link ConfigurationProperties

									 * <code>@ConfigurationProperties</code>}. When these beans are re-bound and

									 * re-initialized the changes are available immediately to any component that is using the

									 * <code>@ConfigurationProperties</code> bean.

									 *

									 * @see RefreshScope for a deeper and optionally more focused refresh of bean components

									 *

									 * @author Dave Syer

									 *

									 */

									@Component

									@ManagedResource

									public class ConfigurationPropertiesRebinder

									  implements ApplicationContextAware, ApplicationListener<EnvironmentChangeEvent> {

									 private ConfigurationPropertiesBeans beans;

									 private ApplicationContext applicationContext;

									 private Map<String, Exception> errors = new ConcurrentHashMap<>();

									 public ConfigurationPropertiesRebinder(ConfigurationPropertiesBeans beans) {

									  this.beans = beans;

									 }

									 @Override

									 public void setApplicationContext(ApplicationContext applicationContext)

									   throws BeansException {

									  this.applicationContext = applicationContext;

									 }

									 /**

									  * A map of bean name to errors when instantiating the bean.

									  *

									  * @return the errors accumulated since the latest destroy

									  */

									 public Map<String, Exception> getErrors() {

									  return this.errors;

									 }

									 @ManagedOperation

									 public void rebind() {

									  this.errors.clear();

									  for (String name : this.beans.getBeanNames()) {

									   rebind(name);

									  }

									 }

									 @ManagedOperation

									 public boolean rebind(String name) {

									  if (!this.beans.getBeanNames().contains(name)) {

									   return false;

									  }

									  if (this.applicationContext != null) {

									   try {

									    Object bean = this.applicationContext.getBean(name);

									    if (AopUtils.isAopProxy(bean)) {

									     bean = getTargetObject(bean);

									    }

									    this.applicationContext.getAutowireCapableBeanFactory().destroyBean(bean);

									    this.applicationContext.getAutowireCapableBeanFactory()

									      .initializeBean(bean, name);

									    return true;

									   }

									   catch (RuntimeException e) {

									    this.errors.put(name, e);

									    throw e;

									   }

									  }

									  return false;

									 }

									 @SuppressWarnings("unchecked")

									 private static <T> T getTargetObject(Object candidate) {

									  try {

									   if (AopUtils.isAopProxy(candidate) && (candidate instanceof Advised)) {

									    return (T) ((Advised) candidate).getTargetSource().getTarget();

									   }

									  }

									  catch (Exception ex) {

									   throw new IllegalStateException("Failed to unwrap proxied object", ex);

									  }

									  return (T) candidate;

									 }

									 @ManagedAttribute

									 public Set<String> getBeanNames() {

									  return new HashSet<String>(this.beans.getBeanNames());

									 }

									 @Override

									 public void onApplicationEvent(EnvironmentChangeEvent event) {

									  if (this.applicationContext.equals(event.getSource())

									    // Backwards compatible

									    || event.getKeys().equals(event.getSource())) {

									   rebind();

									  }

									 }

									}

　　我们可以看到该类监听了ChangeEnvrionmentEvent事件，它最主要作用是拿到更新的配置以后，重新绑定@ConfigurationProperties标记的类使之能够读取最新的属性

　　LoggingRebinder:

				?

									/*

									 * Copyright 2013-2014 the original author or authors.

									 *

									 * Licensed under the Apache License, Version 2.0 (the "License");

									 * you may not use this file except in compliance with the License.

									 * You may obtain a copy of the License at

									 *

									 *  http://www.apache.org/licenses/LICENSE-2.0

									 *

									 * Unless required by applicable law or agreed to in writing, software

									 * distributed under the License is distributed on an "AS IS" BASIS,

									 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

									 * See the License for the specific language governing permissions and

									 * limitations under the License.

									 */

									package org.springframework.cloud.logging;

									import java.util.Map;

									import java.util.Map.Entry;

									import org.apache.commons.logging.Log;

									import org.apache.commons.logging.LogFactory;

									import org.springframework.boot.bind.RelaxedPropertyResolver;

									import org.springframework.boot.logging.LogLevel;

									import org.springframework.boot.logging.LoggingSystem;

									import org.springframework.cloud.context.environment.EnvironmentChangeEvent;

									import org.springframework.context.ApplicationListener;

									import org.springframework.context.EnvironmentAware;

									import org.springframework.core.env.Environment;

									/**

									 * Listener that looks for {@link EnvironmentChangeEvent} and rebinds logger levels if any

									 * changed.

									 *

									 * @author Dave Syer

									 *

									 */

									public class LoggingRebinder

									  implements ApplicationListener<EnvironmentChangeEvent>, EnvironmentAware {

									 private final Log logger = LogFactory.getLog(getClass());

									 private Environment environment;

									 @Override

									 public void setEnvironment(Environment environment) {

									  this.environment = environment;

									 }

									 @Override

									 public void onApplicationEvent(EnvironmentChangeEvent event) {

									  if (this.environment == null) {

									   return;

									  }

									  LoggingSystem system = LoggingSystem.get(LoggingSystem.class.getClassLoader());

									  setLogLevels(system, this.environment);

									 }

									 protected void setLogLevels(LoggingSystem system, Environment environment) {

									  Map<String, Object> levels = new RelaxedPropertyResolver(environment)

									    .getSubProperties("logging.level.");

									  for (Entry<String, Object> entry : levels.entrySet()) {

									   setLogLevel(system, environment, entry.getKey(), entry.getValue().toString());

									  }

									 }

									 private void setLogLevel(LoggingSystem system, Environment environment, String name,

									   String level) {

									  try {

									   if (name.equalsIgnoreCase("root")) {

									    name = null;

									   }

									   level = environment.resolvePlaceholders(level);

									   system.setLogLevel(name, LogLevel.valueOf(level.toUpperCase()));

									  }

									  catch (RuntimeException ex) {

									   this.logger.error("Cannot set level: " + level + " for '" + name + "'");

									  }

									 }

									}

　　该类也是监听了ChangeEnvrionmentEvent事件，用于重新绑定日志级别

二、刷新范围

　　我们考虑如下场景，当我们变更数据库配置后，通过refresh刷新，虽然能获取到最新的配置，可是我们的DataSource对象早就被初始化好了，换句话说即便配置刷新了我们拿到的依然是配置刷新前的对象。怎么解决这个问题呢？

　　我们继续看ContextRefresher的refresh方法，最后有一处代码值得我们关注一下this.scope.refreshAll()，此处scope对象是RefreshScope类型，那么这个类有什么作用呢？那么我们先要关注一下@RefreshScope注解。在这里我在贴出官网一段解释：

　　当配置更改时，标有@RefreshScope的Spring @Bean将得到特殊处理。这解决了状态bean在初始化时只注入配置的问题。例如，如果通过Environment更改数据库URL时DataSource有开放连接，那么我们可能希望这些连接的持有人能够完成他们正在做的工作。然后下一次有人从游泳池借用一个连接，他得到一个新的URL
　　
　　　刷新范围bean是在使用时初始化的懒惰代理（即当调用一个方法时），并且作用域作为初始值的缓存。要强制bean重新初始化下一个方法调用，您只需要使其缓存条目无效。RefreshScope是上下文中的一个bean，它有一个公共方法refreshAll()来清除目标缓存中的范围内的所有bean。还有一个refresh(String)方法可以按名称刷新单个bean。此功能在/refresh端点（通过HTTP或JMX）中公开。

　　这里我贴出@RefreshScope源码：

				?

									/*

									 * Copyright 2013-2014 the original author or authors.

									 *

									 * Licensed under the Apache License, Version 2.0 (the "License");

									 * you may not use this file except in compliance with the License.

									 * You may obtain a copy of the License at

									 *

									 *  http://www.apache.org/licenses/LICENSE-2.0

									 *

									 * Unless required by applicable law or agreed to in writing, software

									 * distributed under the License is distributed on an "AS IS" BASIS,

									 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

									 * See the License for the specific language governing permissions and

									 * limitations under the License.

									 */

									package org.springframework.cloud.context.config.annotation;

									import java.lang.annotation.Documented;

									import java.lang.annotation.ElementType;

									import java.lang.annotation.Retention;

									import java.lang.annotation.RetentionPolicy;

									import java.lang.annotation.Target;

									import org.springframework.context.annotation.Scope;

									import org.springframework.context.annotation.ScopedProxyMode;

									/**

									 * Convenience annotation to put a <code>@Bean</code> definition in

									 * {@link org.springframework.cloud.context.scope.refresh.RefreshScope refresh scope}.

									 * Beans annotated this way can be refreshed at runtime and any components that are using

									 * them will get a new instance on the next method call, fully initialized and injected

									 * with all dependencies.

									 * 

									 * @author Dave Syer

									 *

									 */

									@Target({ ElementType.TYPE, ElementType.METHOD })

									@Retention(RetentionPolicy.RUNTIME)

									@Scope("refresh")

									@Documented

									public @interface RefreshScope {

									 /**

									  * @see Scope#proxyMode()

									  */

									 ScopedProxyMode proxyMode() default ScopedProxyMode.TARGET_CLASS;

									}

　　在这个注解上我们关注一下此处标记了@Scope("refresh")，我们知道Spring的Bean属性有个叫scope的，它定义了bean的作用范围，常见的有singleon,prototype,session等。此处新定义了一个范围叫做refresh，在此我贴出RefreshScope的源代码来分析一下：

				?

									/*

									 * Copyright 2002-2009 the original author or authors.

									 *

									 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with

									 * the License. You may obtain a copy of the License at

									 *

									 * http://www.apache.org/licenses/LICENSE-2.0

									 *

									 * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on

									 * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the

									 * specific language governing permissions and limitations under the License.

									 */

									package org.springframework.cloud.context.scope.refresh;

									import java.io.Serializable;

									import org.springframework.beans.BeansException;

									import org.springframework.beans.factory.config.BeanDefinition;

									import org.springframework.beans.factory.support.BeanDefinitionRegistry;

									import org.springframework.cloud.context.scope.GenericScope;

									import org.springframework.context.ApplicationContext;

									import org.springframework.context.ApplicationContextAware;

									import org.springframework.context.event.ContextRefreshedEvent;

									import org.springframework.context.event.EventListener;

									import org.springframework.core.Ordered;

									import org.springframework.jmx.export.annotation.ManagedOperation;

									import org.springframework.jmx.export.annotation.ManagedResource;

									/**

									 * <p>

									 * A Scope implementation that allows for beans to be refreshed dynamically at runtime

									 * (see {@link #refresh(String)} and {@link #refreshAll()}). If a bean is refreshed then

									 * the next time the bean is accessed (i.e. a method is executed) a new instance is

									 * created. All lifecycle methods are applied to the bean instances, so any destruction

									 * callbacks that were registered in the bean factory are called when it is refreshed, and

									 * then the initialization callbacks are invoked as normal when the new instance is

									 * created. A new bean instance is created from the original bean definition, so any

									 * externalized content (property placeholders or expressions in string literals) is

									 * re-evaluated when it is created.

									 * </p>

									 *

									 * <p>

									 * Note that all beans in this scope are <em>only</em> initialized when first accessed, so

									 * the scope forces lazy initialization semantics. The implementation involves creating a

									 * proxy for every bean in the scope, so there is a flag

									 * {@link #setProxyTargetClass(boolean) proxyTargetClass} which controls the proxy

									 * creation, defaulting to JDK dynamic proxies and therefore only exposing the interfaces

									 * implemented by a bean. If callers need access to other methods then the flag needs to

									 * be set (and CGLib present on the classpath). Because this scope automatically proxies

									 * all its beans, there is no need to add <code>&lt;aop:auto-proxy/&gt;</code> to any bean

									 * definitions.

									 * </p>

									 *

									 * <p>

									 * The scoped proxy approach adopted here has a side benefit that bean instances are

									 * automatically {@link Serializable}, and can be sent across the wire as long as the

									 * receiver has an identical application context on the other side. To ensure that the two

									 * contexts agree that they are identical they have to have the same serialization id. One

									 * will be generated automatically by default from the bean names, so two contexts with

									 * the same bean names are by default able to exchange beans by name. If you need to

									 * override the default id then provide an explicit {@link #setId(String) id} when the

									 * Scope is declared.

									 * </p>

									 *

									 * @author Dave Syer

									 *

									 * @since 3.1

									 *

									 */

									@ManagedResource

									public class RefreshScope extends GenericScope

									  implements ApplicationContextAware, Ordered {

									 private ApplicationContext context;

									 private BeanDefinitionRegistry registry;

									 private boolean eager = true;

									 private int order = Ordered.LOWEST_PRECEDENCE - 100;

									 /**

									  * Create a scope instance and give it the default name: "refresh".

									  */

									 public RefreshScope() {

									  super.setName("refresh");

									 }

									 @Override

									 public int getOrder() {

									  return this.order;

									 }

									 public void setOrder(int order) {

									  this.order = order;

									 }

									 /**

									  * Flag to determine whether all beans in refresh scope should be instantiated eagerly

									  * on startup. Default true.

									  *

									  * @param eager the flag to set

									  */

									 public void setEager(boolean eager) {

									  this.eager = eager;

									 }

									 @Override

									 public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry)

									   throws BeansException {

									  this.registry = registry;

									  super.postProcessBeanDefinitionRegistry(registry);

									 }

									 @EventListener

									 public void start(ContextRefreshedEvent event) {

									  if (event.getApplicationContext() == this.context && this.eager

									    && this.registry != null) {

									   eagerlyInitialize();

									  }

									 }

									 private void eagerlyInitialize() {

									  for (String name : this.context.getBeanDefinitionNames()) {

									   BeanDefinition definition = this.registry.getBeanDefinition(name);

									   if (this.getName().equals(definition.getScope()) && !definition.isLazyInit()) {

									    Object bean = this.context.getBean(name);

									    if (bean != null) {

									     bean.getClass();

									    }

									   }

									  }

									 }

									 @ManagedOperation(description = "Dispose of the current instance of bean name provided and force a refresh on next method execution.")

									 public boolean refresh(String name) {

									  if (!name.startsWith(SCOPED_TARGET_PREFIX)) {

									   // User wants to refresh the bean with this name but that isn't the one in the

									   // cache...

									   name = SCOPED_TARGET_PREFIX + name;

									  }

									  // Ensure lifecycle is finished if bean was disposable

									  if (super.destroy(name)) {

									   this.context.publishEvent(new RefreshScopeRefreshedEvent(name));

									   return true;

									  }

									  return false;

									 }

									 @ManagedOperation(description = "Dispose of the current instance of all beans in this scope and force a refresh on next method execution.")

									 public void refreshAll() {

									  super.destroy();

									  this.context.publishEvent(new RefreshScopeRefreshedEvent());

									 }

									 @Override

									 public void setApplicationContext(ApplicationContext context) throws BeansException {

									  this.context = context;

									 }

									}

　　该类继承了GenericScope：

				?

									/*

									 * Copyright 2002-2009 the original author or authors.

									 *

									 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with

									 * the License. You may obtain a copy of the License at

									 *

									 * http://www.apache.org/licenses/LICENSE-2.0

									 *

									 * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on

									 * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the

									 * specific language governing permissions and limitations under the License.

									 */

									package org.springframework.cloud.context.scope;

									import java.lang.reflect.Method;

									import java.util.ArrayList;

									import java.util.Arrays;

									import java.util.Collection;

									import java.util.Collections;

									import java.util.LinkedHashSet;

									import java.util.List;

									import java.util.Map;

									import java.util.UUID;

									import java.util.concurrent.ConcurrentHashMap;

									import java.util.concurrent.ConcurrentMap;

									import java.util.concurrent.locks.Lock;

									import java.util.concurrent.locks.ReadWriteLock;

									import java.util.concurrent.locks.ReentrantReadWriteLock;

									import org.aopalliance.intercept.MethodInterceptor;

									import org.aopalliance.intercept.MethodInvocation;

									import org.apache.commons.logging.Log;

									import org.apache.commons.logging.LogFactory;

									import org.springframework.aop.framework.Advised;

									import org.springframework.aop.scope.ScopedObject;

									import org.springframework.aop.scope.ScopedProxyFactoryBean;

									import org.springframework.aop.support.AopUtils;

									import org.springframework.beans.BeansException;

									import org.springframework.beans.factory.BeanFactory;

									import org.springframework.beans.factory.DisposableBean;

									import org.springframework.beans.factory.ObjectFactory;

									import org.springframework.beans.factory.config.BeanDefinition;

									import org.springframework.beans.factory.config.BeanFactoryPostProcessor;

									import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;

									import org.springframework.beans.factory.config.Scope;

									import org.springframework.beans.factory.support.BeanDefinitionRegistry;

									import org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor;

									import org.springframework.beans.factory.support.DefaultListableBeanFactory;

									import org.springframework.beans.factory.support.RootBeanDefinition;

									import org.springframework.expression.Expression;

									import org.springframework.expression.ExpressionParser;

									import org.springframework.expression.ParseException;

									import org.springframework.expression.spel.standard.SpelExpressionParser;

									import org.springframework.expression.spel.support.StandardEvaluationContext;

									import org.springframework.util.ReflectionUtils;

									import org.springframework.util.StringUtils;

									/**

									 * <p>

									 * A generic Scope implementation.

									 * </p>

									 *

									 * @author Dave Syer

									 *

									 * @since 3.1

									 *

									 */

									public class GenericScope implements Scope, BeanFactoryPostProcessor,

									  BeanDefinitionRegistryPostProcessor, DisposableBean {

									 private static final Log logger = LogFactory.getLog(GenericScope.class);

									 public static final String SCOPED_TARGET_PREFIX = "scopedTarget.";

									 private BeanLifecycleWrapperCache cache = new BeanLifecycleWrapperCache(

									   new StandardScopeCache());

									 private String name = "generic";

									 private ConfigurableListableBeanFactory beanFactory;

									 private StandardEvaluationContext evaluationContext;

									 private String id;

									 private Map<String, Exception> errors = new ConcurrentHashMap<>();

									 private ConcurrentMap<String, ReadWriteLock> locks = new ConcurrentHashMap<>();

									 /**

									  * Manual override for the serialization id that will be used to identify the bean

									  * factory. The default is a unique key based on the bean names in the bean factory.

									  *

									  * @param id the id to set

									  */

									 public void setId(String id) {

									  this.id = id;

									 }

									 /**

									  * The name of this scope. Default "generic".

									  *

									  * @param name the name value to set

									  */

									 public void setName(String name) {

									  this.name = name;

									 }

									 /**

									  * The cache implementation to use for bean instances in this scope.

									  *

									  * @param cache the cache to use

									  */

									 public void setScopeCache(ScopeCache cache) {

									  this.cache = new BeanLifecycleWrapperCache(cache);

									 }

									 /**

									  * A map of bean name to errors when instantiating the bean.

									  *

									  * @return the errors accumulated since the latest destroy

									  */

									 public Map<String, Exception> getErrors() {

									  return this.errors;

									 }

									 @Override

									 public void destroy() {

									  List<Throwable> errors = new ArrayList<Throwable>();

									  Collection<BeanLifecycleWrapper> wrappers = this.cache.clear();

									  for (BeanLifecycleWrapper wrapper : wrappers) {

									   try {

									    Lock lock = locks.get(wrapper.getName()).writeLock();

									    lock.lock();

									    try {

									     wrapper.destroy();

									    }

									    finally {

									     lock.unlock();

									    }

									   }

									   catch (RuntimeException e) {

									    errors.add(e);

									   }

									  }

									  if (!errors.isEmpty()) {

									   throw wrapIfNecessary(errors.get(0));

									  }

									  this.errors.clear();

									 }

									 /**

									  * Destroy the named bean (i.e. flush it from the cache by default).

									  *

									  * @param name the bean name to flush

									  * @return true if the bean was already cached, false otherwise

									  */

									 protected boolean destroy(String name) {

									  BeanLifecycleWrapper wrapper = this.cache.remove(name);

									  if (wrapper != null) {

									   Lock lock = locks.get(wrapper.getName()).writeLock();

									   lock.lock();

									   try {

									    wrapper.destroy();

									   }

									   finally {

									    lock.unlock();

									   }

									   this.errors.remove(name);

									   return true;

									  }

									  return false;

									 }

									 @Override

									 public Object get(String name, ObjectFactory<?> objectFactory) {

									  BeanLifecycleWrapper value = this.cache.put(name,

									    new BeanLifecycleWrapper(name, objectFactory));

									  locks.putIfAbsent(name, new ReentrantReadWriteLock());

									  try {

									   return value.getBean();

									  }

									  catch (RuntimeException e) {

									   this.errors.put(name, e);

									   throw e;

									  }

									 }

									 @Override

									 public String getConversationId() {

									  return this.name;

									 }

									 @Override

									 public void registerDestructionCallback(String name, Runnable callback) {

									  BeanLifecycleWrapper value = this.cache.get(name);

									  if (value == null) {

									   return;

									  }

									  value.setDestroyCallback(callback);

									 }

									 @Override

									 public Object remove(String name) {

									  BeanLifecycleWrapper value = this.cache.remove(name);

									  if (value == null) {

									   return null;

									  }

									  // Someone might have added another object with the same key, but we

									  // keep the method contract by removing the

									  // value we found anyway

									  return value.getBean();

									 }

									 @Override

									 public Object resolveContextualObject(String key) {

									  Expression expression = parseExpression(key);

									  return expression.getValue(this.evaluationContext, this.beanFactory);

									 }

									 private Expression parseExpression(String input) {

									  if (StringUtils.hasText(input)) {

									   ExpressionParser parser = new SpelExpressionParser();

									   try {

									    return parser.parseExpression(input);

									   }

									   catch (ParseException e) {

									    throw new IllegalArgumentException("Cannot parse expression: " + input,

									      e);

									   }

									  }

									  else {

									   return null;

									  }

									 }

									 @Override

									 public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory)

									   throws BeansException {

									  this.beanFactory = beanFactory;

									  beanFactory.registerScope(this.name, this);

									  setSerializationId(beanFactory);

									 }

									 @Override

									 public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry)

									   throws BeansException {

									  for (String name : registry.getBeanDefinitionNames()) {

									   BeanDefinition definition = registry.getBeanDefinition(name);

									   if (definition instanceof RootBeanDefinition) {

									    RootBeanDefinition root = (RootBeanDefinition) definition;

									    if (root.getDecoratedDefinition() != null && root.hasBeanClass()

									      && root.getBeanClass() == ScopedProxyFactoryBean.class) {

									     if (getName().equals(root.getDecoratedDefinition().getBeanDefinition()

									       .getScope())) {

									      root.setBeanClass(LockedScopedProxyFactoryBean.class);

									     }

									    }

									   }

									  }

									 }

									 /**

									  * If the bean factory is a DefaultListableBeanFactory then it can serialize scoped

									  * beans and deserialize them in another context (even in another JVM), as long as the

									  * ids of the bean factories match. This method sets up the serialization id to be

									  * either the id provided to the scope instance, or if that is null, a hash of all the

									  * bean names.

									  *

									  * @param beanFactory the bean factory to configure

									  */

									 private void setSerializationId(ConfigurableListableBeanFactory beanFactory) {

									  if (beanFactory instanceof DefaultListableBeanFactory) {

									   String id = this.id;

									   if (id == null) {

									    List<String> list = new ArrayList<>(

									      Arrays.asList(beanFactory.getBeanDefinitionNames()));

									    Collections.sort(list);

									    String names = list.toString();

									    logger.debug("Generating bean factory id from names: " + names);

									    id = UUID.nameUUIDFromBytes(names.getBytes()).toString();

									   }

									   logger.info("BeanFactory id=" + id);

									   ((DefaultListableBeanFactory) beanFactory).setSerializationId(id);

									  }

									  else {

									   logger.warn(

									     "BeanFactory was not a DefaultListableBeanFactory, scoped proxy beans "

									       + "cannot be serialized.");

									  }

									 }

									 static RuntimeException wrapIfNecessary(Throwable throwable) {

									  if (throwable instanceof RuntimeException) {

									   return (RuntimeException) throwable;

									  }

									  if (throwable instanceof Error) {

									   throw (Error) throwable;

									  }

									  return new IllegalStateException(throwable);

									 }

									 protected String getName() {

									  return this.name;

									 }

									 private static class BeanLifecycleWrapperCache {

									  private final ScopeCache cache;

									  public BeanLifecycleWrapperCache(ScopeCache cache) {

									   this.cache = cache;

									  }

									  public BeanLifecycleWrapper remove(String name) {

									   return (BeanLifecycleWrapper) this.cache.remove(name);

									  }

									  public Collection<BeanLifecycleWrapper> clear() {

									   Collection<Object> values = this.cache.clear();

									   Collection<BeanLifecycleWrapper> wrappers = new LinkedHashSet<BeanLifecycleWrapper>();

									   for (Object object : values) {

									    wrappers.add((BeanLifecycleWrapper) object);

									   }

									   return wrappers;

									  }

									  public BeanLifecycleWrapper get(String name) {

									   return (BeanLifecycleWrapper) this.cache.get(name);

									  }

									  public BeanLifecycleWrapper put(String name, BeanLifecycleWrapper value) {

									   return (BeanLifecycleWrapper) this.cache.put(name, value);

									  }

									 }

									 /**

									  * Wrapper for a bean instance and any destruction callback (DisposableBean etc.) that

									  * is registered for it. Also decorates the bean to optionally guard it from

									  * concurrent access (for instance).

									  *

									  * @author Dave Syer

									  *

									  */

									 private static class BeanLifecycleWrapper {

									  private Object bean;

									  private Runnable callback;

									  private final String name;

									  private final ObjectFactory<?> objectFactory;

									  public BeanLifecycleWrapper(String name, ObjectFactory<?> objectFactory) {

									   this.name = name;

									   this.objectFactory = objectFactory;

									  }

									  public String getName() {

									   return this.name;

									  }

									  public void setDestroyCallback(Runnable callback) {

									   this.callback = callback;

									  }

									  public Object getBean() {

									   if (this.bean == null) {

									    synchronized (this.name) {

									     if (this.bean == null) {

									      this.bean = this.objectFactory.getObject();

									     }

									    }

									   }

									   return this.bean;

									  }

									  public void destroy() {

									   if (this.callback == null) {

									    return;

									   }

									   synchronized (this.name) {

									    Runnable callback = this.callback;

									    if (callback != null) {

									     callback.run();

									    }

									    this.callback = null;

									    this.bean = null;

									   }

									  }

									  @Override

									  public int hashCode() {

									   final int prime = 31;

									   int result = 1;

									   result = prime * result + ((this.name == null) ? 0 : this.name.hashCode());

									   return result;

									  }

									  @Override

									  public boolean equals(Object obj) {

									   if (this == obj) {

									    return true;

									   }

									   if (obj == null) {

									    return false;

									   }

									   if (getClass() != obj.getClass()) {

									    return false;

									   }

									   BeanLifecycleWrapper other = (BeanLifecycleWrapper) obj;

									   if (this.name == null) {

									    if (other.name != null) {

									     return false;

									    }

									   }

									   else if (!this.name.equals(other.name)) {

									    return false;

									   }

									   return true;

									  }

									 }

									 @SuppressWarnings("serial")

									 public class LockedScopedProxyFactoryBean extends ScopedProxyFactoryBean

									   implements MethodInterceptor {

									  private String targetBeanName;

									  @Override

									  public void setBeanFactory(BeanFactory beanFactory) {

									   super.setBeanFactory(beanFactory);

									   Object proxy = getObject();

									   if (proxy instanceof Advised) {

									    Advised advised = (Advised) proxy;

									    advised.addAdvice(0, this);

									   }

									  }

									  @Override

									  public void setTargetBeanName(String targetBeanName) {

									   super.setTargetBeanName(targetBeanName);

									   this.targetBeanName = targetBeanName;

									  }

									  @Override

									  public Object invoke(MethodInvocation invocation) throws Throwable {

									   Method method = invocation.getMethod();

									   if (AopUtils.isEqualsMethod(method)

									     || AopUtils.isToStringMethod(method)

									     || AopUtils.isHashCodeMethod(method)

									     || isScopedObjectGetTargetObject(method)) {

									    return invocation.proceed();

									   }

									   Object proxy = getObject();

									   Lock lock = locks.get(this.targetBeanName).readLock();

									   lock.lock();

									   try {

									    if (proxy instanceof Advised) {

									     Advised advised = (Advised) proxy;

									     ReflectionUtils.makeAccessible(method);

									     return ReflectionUtils.invokeMethod(method,

									       advised.getTargetSource().getTarget(),

									       invocation.getArguments());

									    }

									    return invocation.proceed();

									   }

									   finally {

									    lock.unlock();

									   }

									  }

									  private boolean isScopedObjectGetTargetObject(Method method) {

									   return method.getDeclaringClass().equals(ScopedObject.class)

									     && method.getName().equals("getTargetObject")

									     && method.getParameterTypes().length == 0;

									  }

									 }

									}

这里面我们先看一下RefreshScope的构造函数：

				?

									/**

									  * Create a scope instance and give it the default name: "refresh".

									  */

									 public RefreshScope() {

									  super.setName("refresh");

									 }

　　这里面创建了一个名字为refresh的scope。

　　紧接着在它的父类里我们可以看一下这个方法：

				?

									@Override

									public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory)

									  throws BeansException {

									 this.beanFactory = beanFactory;

									 beanFactory.registerScope(this.name, this);

									 setSerializationId(beanFactory);

									}

　　此方法中使用BeanFactory注册了一个refresh的范围，使得scope为refresh的bean生效。@RefreshScope标注的类还有一个特点：会使用代理对象并进行延迟加载。我们来看一下postProcessBeanDefinitionRegistry方法

				?

									@Override

									 public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry)

									   throws BeansException {

									  for (String name : registry.getBeanDefinitionNames()) {

									   BeanDefinition definition = registry.getBeanDefinition(name);

									   if (definition instanceof RootBeanDefinition) {

									    RootBeanDefinition root = (RootBeanDefinition) definition;

									    if (root.getDecoratedDefinition() != null && root.hasBeanClass()

									      && root.getBeanClass() == ScopedProxyFactoryBean.class) {

									     if (getName().equals(root.getDecoratedDefinition().getBeanDefinition()

									       .getScope())) {

									      root.setBeanClass(LockedScopedProxyFactoryBean.class);

									     }

									    }

									   }

									  }

									 }

　　该方法遍历所有的bean定义如果当前的bean的scope为refresh,那么就把当前的bean设置为 LockedScopedProxyFactoryBean的代理对象。

　　RefreshScope还会监听一个ContextRefreshedEvent，该事件会在ApplicationContext初始化或者refreshed时触发，我们来看一下代码：

				?

									@EventListener

									 public void start(ContextRefreshedEvent event) {

									  if (event.getApplicationContext() == this.context && this.eager

									    && this.registry != null) {

									   eagerlyInitialize();

									  }

									 }

									 private void eagerlyInitialize() {

									  for (String name : this.context.getBeanDefinitionNames()) {

									   BeanDefinition definition = this.registry.getBeanDefinition(name);

									   if (this.getName().equals(definition.getScope()) && !definition.isLazyInit()) {

									    Object bean = this.context.getBean(name);

									    if (bean != null) {

									     bean.getClass();

									    }

									   }

									  }

									 }

　　注意此处获取refreshscope的bean，其中getBean是一个复杂而又繁琐的过程，此处我们先不在这里讨论，只不过经过这个方法以后，其通过代理机制会在GernericScope的BeanLifecycleWrapperCache缓存里把这个@RefreshScope标记的bean添加进去。

　　最后我们回过头来看一看RefreshScope的refreshAll方法：

				?

									@ManagedOperation(description = "Dispose of the current instance of all beans in this scope and force a refresh on next method execution.")

									 public void refreshAll() {

									  super.destroy();

									  this.context.publishEvent(new RefreshScopeRefreshedEvent());

									 }

									//.......GernericScope的destroy方法

									 @Override

									 public void destroy() {

									  List<Throwable> errors = new ArrayList<Throwable>();

									  Collection<BeanLifecycleWrapper> wrappers = this.cache.clear();

									  for (BeanLifecycleWrapper wrapper : wrappers) {

									   try {

									    Lock lock = locks.get(wrapper.getName()).writeLock();

									    lock.lock();

									    try {

									     wrapper.destroy();

									    }

									    finally {

									     lock.unlock();

									    }

									   }

									   catch (RuntimeException e) {

									    errors.add(e);

									   }

									  }

									  if (!errors.isEmpty()) {

									   throw wrapIfNecessary(errors.get(0));

									  }

									  this.errors.clear();

									 }

　　这里的代码逻辑很简单清除与释放缓存里被@RefreshScope标记的bean 。

　　当我们要获取对象时，我们可以关注如下方法：

				?

									@Override

									 public Object get(String name, ObjectFactory<?> objectFactory) {

									  BeanLifecycleWrapper value = this.cache.put(name,

									    new BeanLifecycleWrapper(name, objectFactory));

									  locks.putIfAbsent(name, new ReentrantReadWriteLock());

									  try {

									   return value.getBean();

									  }

									  catch (RuntimeException e) {

									   this.errors.put(name, e);

									   throw e;

									  }

									 }  

									//..... BeanLifecycleWrapper的方法

									  public Object getBean() {

									   if (this.bean == null) {

									    synchronized (this.name) {

									     if (this.bean == null) {

									      this.bean = this.objectFactory.getObject();

									     }

									    }

									   }

									   return this.bean;

									  }

BeanLifecycleWrapper这个是@RefreshScope标记bean的一个包装类，会被存储到缓存里，在这里取不到值的话就会从objectFactory里去拿

三、示例与总结

3.1、示例

　　创建AppConfig类代码如下：

				?

									package com.bdqn.lyrk.refresh.scope.server;

									import org.springframework.boot.context.properties.EnableConfigurationProperties;

									import org.springframework.cloud.context.config.annotation.RefreshScope;

									import org.springframework.context.annotation.Bean;

									import org.springframework.context.annotation.Configuration;

									@Configuration

									@EnableConfigurationProperties(StudentConfig.class)

									public class AppConfig {

									 @RefreshScope

									 @Bean

									 public Student student(StudentConfig config) {

									  Student student = new Student();

									  student.setName(config.getName());

									  return student;

									 }

									}

　　在这里，将Student设置为@RefreshScope 那么刷新以后会获取最新的Bean

　　启动类：

				?

									package com.bdqn.lyrk.refresh.scope.server;

									import org.springframework.beans.factory.annotation.Autowired;

									import org.springframework.boot.SpringApplication;

									import org.springframework.boot.autoconfigure.SpringBootApplication;

									import org.springframework.web.bind.annotation.GetMapping;

									import org.springframework.web.bind.annotation.RestController;

									@SpringBootApplication

									@RestController

									public class RefreshScopeApplication {

									 @Autowired

									 private Student student;

									 @GetMapping

									 public String student() {

									  return student.getName();

									 }

									 public static void main(String[] args) throws InterruptedException {

									  SpringApplication.run(RefreshScopeApplication.class, args);

									 }

									}

　　application.yml文件：

				?

									spring:

									 application:

									 name: refresh-scope-server

									endpoints:

									 refresh:

									 sensitive: false

									server:

									 port: 8089

									student:

									 name: admin

　　这里把refresh端点开放出来，然后变更配置后就可以获取最新的对象了

3.2、总结

　　1) 当配置更新并通过refresh端点刷新后，会执行ContextRefresher的refresh方法，该方法会记录当前的Environment，而后构建一个简易的SpringApplicationBuilder并执行其run方法，此时ConfigFileApplicationListener会读取我们修改过后的配置并绑定到SpringApplication对象上，最后进行changes操作来变更已有的PropertySource

　　2) @RefreshScope最好配合@Bean使用，当且仅当变更配置后，需要重新获取最新的bean时使用。加上该注解的Bean会被代理并且延迟加载，所有的scope属性为Refresh的bean会被包装成BeanLifecycleWrapper存入缓存(ConcurrentHashMap)中,所有的读取，修改，删除都是基于该缓存的。

总结

以上所述是小编给大家介绍的SpringCloud配置刷新原理解析，希望对大家有所帮助，如果大家有任何疑问欢迎给我留言，小编会及时回复大家的！

原文链接：http://www.cnblogs.com/niechen/p/8979578.html

SpringCloud配置刷新原理解析

相关文章

热门资讯