Java使用HttpClient实现Post请求实例

基于项目需求，想要实现Post消息推送，故采用HttpClient组件进行实现，相关代码如下(注：程序采用的httpclient和httpcore依赖包的版本为4.2.5)：

import org.apache.http.Header;
import org.apache.http.HttpResponse;
import org.apache.http.HttpStatus;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.params.CoreConnectionPNames;
import java.util.UUID;
import net.sf.json.JSONObject;
import java.nio.charset.Charset;

public static boolean httpPostWithJson(JSonObject jsonObj,String url,String appId){
  boolean isSuccess = false;
  
  HttpPost post = null;
  try {
    HttpClient httpClient = new DefaultHttpClient();

    // 设置超时时间
    httpClient.getParams().setParameter(CoreConnectionPNames.CONNECTION_TIMEOUT, 2000);
    httpClient.getParams().setParameter(CoreConnectionPNames.SO_TIMEOUT, 2000);
      
    post = new HttpPost(url);
    // 构造消息头
    post.setHeader("Content-type", "application/json; charset=utf-8");
    post.setHeader("Connection", "Close");
    String sessionId = getSessionId();
    post.setHeader("SessionId", sessionId);
    post.setHeader("appid", appid);
   
    // 构建消息实体
    StringEntity entity = new StringEntity(jsonObj.toString(), Charset.forName("UTF-8"));
    entity.setContentEncoding("UTF-8");
    // 发送Json格式的数据请求
    entity.setContentType("application/json");
    post.setEntity(entity);
      
    HttpResponse response = httpClient.execute(post);
      
    // 检验返回码
    int statusCode = response.getStatusLine().getStatusCode();
    if(statusCode != HttpStatus.SC_OK){
      LogUtil.info("请求出错: "+statusCode);
      isSuccess = false;
    }else{
      int retCode = 0;
      String sessendId = "";
      // 返回码中包含retCode及会话Id
      for(Header header : response.getAllHeaders()){
 if(header.getName().equals("retcode")){
   retCode = Integer.parseInt(header.getValue());
 }
 if(header.getName().equals("SessionId")){
   sessendId = header.getValue();
 }
      }
      
      if(ErrorCodeHelper.IAS_SUCCESS != retCode ){
 // 日志打印
 LogUtil.info("error return code, sessionId: "sessendId"t"+"retCode: "+retCode);
 isSuccess = false;
      }else{
 isSuccess = true;
      }
    }
  } catch (Exception e) {
    e.printStackTrace();
    isSuccess = false;
  }finally{
    if(post != null){
      try {
 post.releaseConnection();
 Thread.sleep(500);
      } catch (InterruptedException e) {
 e.printStackTrace();
      }
    }
  }
  return isSuccess;
}

// 构建唯一会话Id
public static String getSessionId(){
  UUID uuid = UUID.randomUUID();
  String str = uuid.toString();
  return str.substring(0, 8) + str.substring(9, 13) + str.substring(14, 18) + str.substring(19, 23) + str.substring(24);
}

Ps: 在使用Hadoop集群进行发送POST请求时，遇到"java.lang.NoSuchFieldError: INSTANCE"的问题，此类问题一般是"jar包冲突"的问题所致，但奇怪的是本地的pom.xml设置的依赖包中有该字段，相关的httpclient依赖包如下：　　

  org.apache.httpcomponents
  httpclient
  4.4.1


  org.apache.httpcomponents
  httpcore
  4.4.1
  

随后在网上查找了一翻，找到问题的缘由，原因在于Hadoop集群运行程序时，首先会加载自己相关目录下的jar包，在自己目录下如果未找到，才会加载程序运行时指定的jar包，随查找了Hadoop集群中相关Jar包路径，发现httpclient的相关依赖包为4.2.5，因此将pom.xml配置文件也更新为该版本，程序则运行通过.

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