微服系列之Feign使用HttpClient和OkHttp网络请求框架

Feign实现了远程调用，底层默认使用的是HttpURLConnection网络请求框架

那Feign支不支持其他的网络请求框架呢，答案那是肯定的，Feign还支持HttpClient和OkHttp，

那Feign中怎么将请求框架切换到另外两种呢，首先我们先查看一下Feign配置类

@ConditionalOnClass({ILoadBalancer.class, Feign.class})@Configuration@AutoConfigureBefore({FeignAutoConfiguration.class})public class FeignRibbonClientAutoConfiguration {public FeignRibbonClientAutoConfiguration() {}@Bean@Primary@ConditionalOnMissingClass({"org.springframework.retry.support.RetryTemplate"})public CachingSpringLoadBalancerFactory cachingLBClientFactory(SpringClientFactory factory) {return new CachingSpringLoadBalancerFactory(factory);}@Bean@Primary@ConditionalOnClass(name = {"org.springframework.retry.support.RetryTemplate"})public CachingSpringLoadBalancerFactory retryabeCachingLBClientFactory(SpringClientFactory factory, LoadBalancedRetryPolicyFactory retryPolicyFactory) {return new CachingSpringLoadBalancerFactory(factory, retryPolicyFactory, true);}@Bean@ConditionalOnMissingBeanpublic Client feignClient(CachingSpringLoadBalancerFactory cachingFactory, SpringClientFactory clientFactory) {return new LoadBalancerFeignClient(new Default((SSLSocketFactory)null, (HostnameVerifier)null), cachingFactory, clientFactory);}@Bean@ConditionalOnMissingBeanpublic Options feignRequestOptions() {return LoadBalancerFeignClient.DEFAULT_OPTIONS;}@Configuration@ConditionalOnClass({OkHttpClient.class})@ConditionalOnProperty(value = {"feign.okhttp.enabled"},matchIfMissing = true)protected static class OkHttpFeignLoadBalancedConfiguration {@Autowired(required = false)private okhttp3.OkHttpClient okHttpClient;protected OkHttpFeignLoadBalancedConfiguration() {}@Bean@ConditionalOnMissingBean({Client.class})public Client feignClient(CachingSpringLoadBalancerFactory cachingFactory, SpringClientFactory clientFactory) {OkHttpClient delegate;if (this.okHttpClient != null) {delegate = new OkHttpClient(this.okHttpClient);} else {delegate = new OkHttpClient();}return new LoadBalancerFeignClient(delegate, cachingFactory, clientFactory);}}@Configuration@ConditionalOnClass({ApacheHttpClient.class})@ConditionalOnProperty(value = {"feign.httpclient.enabled"},matchIfMissing = true)protected static class HttpClientFeignLoadBalancedConfiguration {@Autowired(required = false)private HttpClient httpClient;protected HttpClientFeignLoadBalancedConfiguration() {}@Bean@ConditionalOnMissingBean({Client.class})public Client feignClient(CachingSpringLoadBalancerFactory cachingFactory, SpringClientFactory clientFactory) {ApacheHttpClient delegate;if (this.httpClient != null) {delegate = new ApacheHttpClient(this.httpClient);} else {delegate = new ApacheHttpClient();}return new LoadBalancerFeignClient(delegate, cachingFactory, clientFactory);}}}

我们着重看一下方法名为：HttpClientFeignLoadBalancedConfiguration，从代码上来看@ConditionalOnClass({ApacheHttpClient.class})这个注解可以知道，只需要在pom文件中加上HttpClient的ClassPath即可，另外需要在配置文件application.yml或application.properties中配置上feign.httpclinet.enabled=true即可，从注解@ConditionalOnProperty注解可知，这个配置可以不写，因为在默认的情况下就是true，接下来实现：

在工程pom文件中添加feign-httpclient的依赖，Feign就会采用HttpClient作为网络请求框架，而不是默认的HttpURLConnection，依赖如下：

com.netflix.feign
feign-httpclient
RELEASE

同理，如果想使用Okhttp作为网络请求框架，只需要在pom中添加feign-okhttp的依赖即可，依赖如下：

com.netflix.feign
feign-okhttp
RELEASE