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：

<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.

来源：http://www.cnblogs.com/mengrennwpu/p/6418114.html