背景
数据库配置主从之后，如何在代码层面实现读写分离？
用户自定义设置数据库路由
Spring boot提供了AbstractRoutingDataSource根据用户定义的规则选择当前的数据库，这样我们可以在执行查询之前，设置读取从库，在执行完成后，恢复到主库。
实现可动态路由的数据源，在每次数据库查询操作前执行
ReadWriteSplitRoutingDataSource.java
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import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;/** * @author songrgg * @since 1.0 */public class ReadWriteSplitRoutingDataSource extends AbstractRoutingDataSource { @Override protected Object determineCurrentLookupKey() { return DbContextHolder.getDbType(); }} |
线程私有路由配置，用于ReadWriteSplitRoutingDataSource动态读取配置
DbContextHolder.java
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/** * @author songrgg * @since 1.0 */public class DbContextHolder { public enum DbType { MASTER, SLAVE } private static final ThreadLocal<DbType> contextHolder = new ThreadLocal<>(); public static void setDbType(DbType dbType) { if(dbType == null){ throw new NullPointerException(); } contextHolder.set(dbType); } public static DbType getDbType() { return contextHolder.get() == null ? DbType.MASTER : contextHolder.get(); } public static void clearDbType() { contextHolder.remove(); }} |
AOP优化代码
利用AOP将设置数据库的操作从代码中抽离，这里的粒度控制在方法级别，所以利用注解的形式标注这个方法涉及的数据库事务只读，走从库。
只读注解，用于标注方法的数据库操作只走从库。
ReadOnlyConnection.java
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package com.wallstreetcn.hatano.config;import java.lang.annotation.ElementType;import java.lang.annotation.Retention;import java.lang.annotation.RetentionPolicy;import java.lang.annotation.Target;/** * Indicates the database operations is bound to the slave database. * AOP interceptor will set the database to the slave with this interface. * @author songrgg * @since 1.0 */@Target({ElementType.METHOD, ElementType.TYPE})@Retention(RetentionPolicy.RUNTIME)public @interface ReadOnlyConnection {} |
ReadOnlyConnectionInterceptor.java
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import org.aspectj.lang.ProceedingJoinPoint;import org.aspectj.lang.annotation.Around;import org.aspectj.lang.annotation.Aspect;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import org.springframework.core.Ordered;import org.springframework.stereotype.Component;/** * Intercept the database operations, bind database to read-only database as this annotation * is applied. * @author songrgg * @since 1.0 */@Aspect@Componentpublic class ReadOnlyConnectionInterceptor implements Ordered { private static final Logger logger = LoggerFactory.getLogger(ReadOnlyConnectionInterceptor.class); @Around("@annotation(readOnlyConnection)") public Object proceed(ProceedingJoinPoint proceedingJoinPoint, ReadOnlyConnection readOnlyConnection) throws Throwable { try { logger.info("set database connection to read only"); DbContextHolder.setDbType(DbContextHolder.DbType.SLAVE); Object result = proceedingJoinPoint.proceed(); return result; } finally { DbContextHolder.clearDbType(); logger.info("restore database connection"); } } @Override public int getOrder() { return 0; }} |
UserService.java
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@ReadOnlyConnectionpublic List<User> getUsers(Integer page, Integer limit) { return repository.findAll(new PageRequest(page, limit));} |
配置Druid数据库连接池
build.gradle
compile("com.alibaba:druid:1.0.18")
groovy依赖注入
配置dataSource为可路由数据源
context.groovy
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import com.alibaba.druid.pool.DruidDataSourceimport DbContextHolderimport ReadWriteSplitRoutingDataSource** SOME INITIALIZED CODE LOAD PROPERTIES **def dataSourceMaster = new DruidDataSource()dataSourceMaster.url = properties.get('datasource.master.url')println("master set to " + dataSourceMaster.url)dataSourceMaster.username = properties.get('datasource.master.username')dataSourceMaster.password = properties.get('datasource.master.password')def dataSourceSlave = new DruidDataSource()dataSourceSlave.url = properties.get('datasource.slave.url')println("slave set to " + dataSourceSlave.url)dataSourceSlave.username = properties.get('datasource.slave.username')dataSourceSlave.password = properties.get('datasource.slave.password') beans { dataSource(ReadWriteSplitRoutingDataSource) { bean -> targetDataSources = [ (DbContextHolder.DbType.MASTER): dataSourceMaster, (DbContextHolder.DbType.SLAVE): dataSourceSlave ] }} |
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持服务器之家。
原文链接：http://www.cnblogs.com/pier2/p/spring-boot-read-write-split.html
