Java使用HttpClient實現Post請求實例

基於項目需求，想要實現Post消息推送，故采用HttpClient組件進行實現，相關代碼如下(注：程序采用的httpclient和httpcore依賴包的版本為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();

    // 設置超時時間
    httpClient.getParams().setParameter(CoreConnectionPNames.CONNECTION_TIMEOUT, 2000);
    httpClient.getParams().setParameter(CoreConnectionPNames.SO_TIMEOUT, 2000);
      
    post = new HttpPost(url);
    // 構造消息頭
    post.setHeader("Content-type", "application/json; charset=utf-8");
    post.setHeader("Connection", "Close");
    String sessionId = getSessionId();
    post.setHeader("SessionId", sessionId);
    post.setHeader("appid", appid);
          
    // 構建消息實體
    StringEntity entity = new StringEntity(jsonObj.toString(), Charset.forName("UTF-8"));
    entity.setContentEncoding("UTF-8");
    // 發送Json格式的數據請求
    entity.setContentType("application/json");
    post.setEntity(entity);
      
    HttpResponse response = httpClient.execute(post);
      
    // 檢驗返回碼
    int statusCode = response.getStatusLine().getStatusCode();
    if(statusCode != HttpStatus.SC_OK){
      LogUtil.info("請求出錯: "+statusCode);
      isSuccess = false;
    }else{
      int retCode = 0;
      String sessendId = "";
      // 返回碼中包含retCode及會話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;
}

// 構建唯一會話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集群進行發送POST請求時，遇到"java.lang.NoSuchFieldError: INSTANCE"的問題，此類問題一般是"jar包沖突"的問題所致，但奇怪的是本地的pom.xml設置的依賴包中有該字段，相關的httpclient依賴包如下：　　

<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>  

隨後在網上查找了一翻，找到問題的緣由，原因在於Hadoop集群運行程序時，首先會加載自己相關目錄下的jar包，在自己目錄下如果未找到，才會加載程序運行時指定的jar包，隨查找了Hadoop集群中相關Jar包路徑，發現httpclient的相關依賴包為4.2.5，因此將pom.xml配置文件也更新為該版本，程序則運行通過.

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