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Idpublic 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：　　

<dependency> <groupId>org.apache.httpcomponents</groupId> <artifactId>httpclient</artifactId> <version>4.4.1</version></dependency><dependency> <groupId>org.apache.httpcomponents</groupId> <artifactId>httpcore</artifactId> <version>4.4.1</version></dependency>

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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