spring boot封装HttpClient的示例代码

最近使用到了HttpClient，看了一下官方文档：HttpClient implementations are expected to be thread safe. It is recommended that the same instance of this class is reused for multiple request executions，翻译过来的意思就是：HttpClient的实现是线程安全的，可以重用相同的实例来执行多次请求。遇到这种描述的话，我们就应该想到，需要对HttpClient来进行封装了。由于是使用的spring boot，所以下面来结合spring boot来封装HttpClient。

一、Request retry handler(请求重试处理)

为了使自定义异常机制生效，需要实现HttpRequestRetryHandler接口，代码如下：

import java.io.IOException; import java.io.InterruptedIOException; import java.net.UnknownHostException; import javax.net.ssl.SSLException; import javax.net.ssl.SSLHandshakeException; import org.apache.http.HttpEntityEnclosingRequest; import org.apache.http.HttpRequest; import org.apache.http.NoHttpResponseException; import org.apache.http.client.HttpRequestRetryHandler; import org.apache.http.client.protocol.HttpClientContext; import org.apache.http.conn.ConnectTimeoutException; import org.apache.http.protocol.HttpContext; import org.springframework.beans.factory.annotation.Value; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration;  /**  * 描述：HttpClient的重试处理机制  */ @Configuration public class MyhttpRequestRetryHandler {    @Value("${httpclient.config.retryTime}")// 此处建议采用@ConfigurationProperties(prefix="httpclient.config")方式，方便复用   private int retryTime;      @Bean   public HttpRequestRetryHandler httpRequestRetryHandler() {     // 请求重试     final int retryTime = this.retryTime;     return new HttpRequestRetryHandler() {       public boolean retryRequest(IOException exception, int executionCount, HttpContext context) {         // Do not retry if over max retry count,如果重试次数超过了retryTime,则不再重试请求         if (executionCount >= retryTime) {           return false;         }         // 服务端断掉客户端的连接异常         if (exception instanceof NoHttpResponseException) {           return true;         }         // time out 超时重试         if (exception instanceof InterruptedIOException) {           return true;         }         // Unknown host         if (exception instanceof UnknownHostException) {           return false;         }         // Connection refused         if (exception instanceof ConnectTimeoutException) {           return false;         }         // SSL handshake exception         if (exception instanceof SSLException) {           return false;         }         HttpClientContext clientContext = HttpClientContext.adapt(context);         HttpRequest request = clientContext.getRequest();         if (!(request instanceof HttpEntityEnclosingRequest)) {           return true;         }         return false;       }     };   } } 

二、Pooling connection manager(连接池管理)

PoolingHttpClientConnectionManager用来管理客户端的连接池，并且可以为多个线程的请求提供服务，代码如下：