http://www.cnblogs.com/mengrennwpu/p/6418114.html
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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(具体参见：http://bbs.umeng.com/thread-12187-1-1.html)，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.