Feign 使用HttpClient和OkHttp方式

使用HttpClient和OkHttp

在Feign中，Client是一个非常重要的组件，Feign最终发送Request请求以及接收Response响应都是由Client组件来完成的。Client在Feign源码中是一个接口，在默认情况下，Client的实现类是Client.Default。Client.Default是由HttpURLConnection来实现网络请求的。另外,Client还支持HttpClient和OkHttp来进行网络请求。

首先查看FeignRibbonClient的自动配置类FeignRibbonClientAutoConfiguration，该类在程序启动的时候注入一些Bean，其中注入了一个BeanName为feignClient的Client类型的Bean。在省缺配置BeanName为FeignClient的Bean的情况下，会自动注入Client.Default这个对象，跟踪Client.Default源码,Client.Default使用的网络请求框架是HttpURLConnection，代码如下：

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									public static class Default implements Client {

									        private final SSLSocketFactory sslContextFactory;

									        private final HostnameVerifier hostnameVerifier;

									        public Default(SSLSocketFactory sslContextFactory, HostnameVerifier hostnameVerifier) {

									            this.sslContextFactory = sslContextFactory;

									            this.hostnameVerifier = hostnameVerifier;

									        }

									        public Response execute(Request request, Options options) throws IOException {

									            HttpURLConnection connection = this.convertAndSend(request, options);

									            return this.convertResponse(connection, request);

									        }        

									        ......//代码省略

									}

这种情况下，由于缺乏连接池的支持，在达到一定流量的后服务肯定会出问题。

使用HttpClient

那么如何在Feign中使用HttpClient的框架呢？我们查看FeignAutoConfiguration.HttpClientFeignConfiguration的源码：

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									@Configuration

									@ConditionalOnClass({ApacheHttpClient.class})

									@ConditionalOnMissingClass({"com.netflix.loadbalancer.ILoadBalancer"})

									@ConditionalOnMissingBean({CloseableHttpClient.class})

									@ConditionalOnProperty(

									    value = {"feign.httpclient.enabled"},

									    matchIfMissing = true

									)

									protected static class HttpClientFeignConfiguration {

									    private final Timer connectionManagerTimer = new Timer("FeignApacheHttpClientConfiguration.connectionManagerTimer", true);

									    @Autowired(

									        required = false

									    )

									    private RegistryBuilder registryBuilder;

									    private CloseableHttpClient httpClient;

									    protected HttpClientFeignConfiguration() {

									    }

									    @Bean

									    @ConditionalOnMissingBean({HttpClientConnectionManager.class})

									    public HttpClientConnectionManager connectionManager(ApacheHttpClientConnectionManagerFactory connectionManagerFactory, FeignHttpClientProperties httpClientProperties) {

									        final HttpClientConnectionManager connectionManager = connectionManagerFactory.newConnectionManager(httpClientProperties.isDisableSslValidation(), httpClientProperties.getMaxConnections(), httpClientProperties.getMaxConnectionsPerRoute(), httpClientProperties.getTimeToLive(), httpClientProperties.getTimeToLiveUnit(), this.registryBuilder);

									        this.connectionManagerTimer.schedule(new TimerTask() {

									            public void run() {

									                connectionManager.closeExpiredConnections();

									            }

									        }, 30000L, (long)httpClientProperties.getConnectionTimerRepeat());

									        return connectionManager;

									    }

									    @Bean

									    public CloseableHttpClient httpClient(ApacheHttpClientFactory httpClientFactory, HttpClientConnectionManager httpClientConnectionManager, FeignHttpClientProperties httpClientProperties) {

									        RequestConfig defaultRequestConfig = RequestConfig.custom().setConnectTimeout(httpClientProperties.getConnectionTimeout()).setRedirectsEnabled(httpClientProperties.isFollowRedirects()).build();

									        this.httpClient = httpClientFactory.createBuilder().setConnectionManager(httpClientConnectionManager).setDefaultRequestConfig(defaultRequestConfig).build();

									        return this.httpClient;

									    }

									    @Bean

									    @ConditionalOnMissingBean({Client.class})

									    public Client feignClient(HttpClient httpClient) {

									        return new ApacheHttpClient(httpClient);

									    }

									    @PreDestroy

									    public void destroy() throws Exception {

									        this.connectionManagerTimer.cancel();

									        if (this.httpClient != null) {

									            this.httpClient.close();

									        }

									    }

									}

从代码@ConditionalOnClass({ApacheHttpClient.class})注解可知，只需要在pom文件上加上HttpClient依赖即可。另外需要在配置文件中配置feign.httpclient.enabled为true，从@ConditionalOnProperty注解可知，这个配置可以不写，因为在默认情况下就为true:

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									<dependency>

									    <groupId>io.github.openfeign</groupId>

									    <artifactId>feign-httpclient</artifactId>

									    <version>9.4.0</version>

									</dependency>

使用OkHttp

查看FeignAutoConfiguration.HttpClientFeignConfiguration的源码：

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									@Configuration

									@ConditionalOnClass({OkHttpClient.class})

									@ConditionalOnMissingClass({"com.netflix.loadbalancer.ILoadBalancer"})

									@ConditionalOnMissingBean({okhttp3.OkHttpClient.class})

									@ConditionalOnProperty({"feign.okhttp.enabled"})

									protected static class OkHttpFeignConfiguration {

									    private okhttp3.OkHttpClient okHttpClient;

									    protected OkHttpFeignConfiguration() {

									    }

									    @Bean

									    @ConditionalOnMissingBean({ConnectionPool.class})

									    public ConnectionPool httpClientConnectionPool(FeignHttpClientProperties httpClientProperties, OkHttpClientConnectionPoolFactory connectionPoolFactory) {

									        Integer maxTotalConnections = httpClientProperties.getMaxConnections();

									        Long timeToLive = httpClientProperties.getTimeToLive();

									        TimeUnit ttlUnit = httpClientProperties.getTimeToLiveUnit();

									        return connectionPoolFactory.create(maxTotalConnections, timeToLive, ttlUnit);

									    }

									    @Bean

									    public okhttp3.OkHttpClient client(OkHttpClientFactory httpClientFactory, ConnectionPool connectionPool, FeignHttpClientProperties httpClientProperties) {

									        Boolean followRedirects = httpClientProperties.isFollowRedirects();

									        Integer connectTimeout = httpClientProperties.getConnectionTimeout();

									        Boolean disableSslValidation = httpClientProperties.isDisableSslValidation();

									        this.okHttpClient = httpClientFactory.createBuilder(disableSslValidation).connectTimeout((long)connectTimeout, TimeUnit.MILLISECONDS).followRedirects(followRedirects).connectionPool(connectionPool).build();

									        return this.okHttpClient;

									    }

									    @PreDestroy

									    public void destroy() {

									        if (this.okHttpClient != null) {

									            this.okHttpClient.dispatcher().executorService().shutdown();

									            this.okHttpClient.connectionPool().evictAll();

									        }

									    }

									    @Bean

									    @ConditionalOnMissingBean({Client.class})

									    public Client feignClient(okhttp3.OkHttpClient client) {

									        return new OkHttpClient(client);

									    }

									}

同理，如果想要在Feign中使用OkHttp作为网络请求框架，则只需要在pom文件中加上feign-okhttp的依赖，代码如下：

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									<dependency>

									    <groupId>io.github.openfeign</groupId>

									    <artifactId>feign-okhttp</artifactId>

									    <version>10.2.0</version>

									</dependency>

OpenFeign替换为OkHttp

pom中引入feign-okhttp

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									<dependency>

									    <groupId>io.github.openfeign</groupId>

									    <artifactId>feign-okhttp</artifactId>

									</dependency>

在application.yml中配置okhttp

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									feign:

									  httpclient:

									    connection-timeout: 2000  #单位ms,默认2000

									    max-connections: 200 #线程池最大连接数

									  okhttp:

									    enabled: true