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：