java 通过发送json,post请求,返回json数据

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import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;

import org.json.JSONArray;
import org.json.JSONObject;

public class GetJsonData {

	public static String getJsonData(JSONObject jsonParam,String urls) {
		StringBuffer sb=new StringBuffer();
		try {
			;
			// 创建url资源
			URL url = new URL(urls);
			// 建立http连接
			HttpURLConnection conn = (HttpURLConnection) url.openConnection();
			// 设置允许输出
			conn.setDoOutput(true);
                        // 设置允许输入
                        conn.setDoInput(true);
                       // 设置不用缓存
                       conn.setUseCaches(false);
                       // 设置传递方式
                       conn.setRequestMethod("POST");
                       // 设置维持长连接
                        conn.setRequestProperty("Connection", "Keep-Alive");
                       // 设置文件字符集:
                       conn.setRequestProperty("Charset", "UTF-8");
                       // 转换为字节数组
                       byte[] data = (jsonParam.toString()).getBytes();
                      // 设置文件长度
                       conn.setRequestProperty("Content-Length", String.valueOf(data.length));
                      // 设置文件类型:
                      conn.setRequestProperty("contentType", "application/json");
                        // 开始连接请求
                       conn.connect();		
                    OutputStream out = new DataOutputStream(conn.getOutputStream()) ;
			// 写入请求的字符串
			out.write((jsonParam.toString()).getBytes());
			out.flush();
			out.close();

			System.out.println(conn.getResponseCode());
			
			// 请求返回的状态
			if (HttpURLConnection.HTTP_OK == conn.getResponseCode(){
				System.out.println("连接成功");
				// 请求返回的数据
				InputStream in1 = conn.getInputStream();
				try {
				      String readLine=new String();
				      BufferedReader responseReader=new BufferedReader(new InputStreamReader(in1,"UTF-8"));
				      while((readLine=responseReader.readLine())!=null){
				        sb.append(readLine).append("\n");
				      }
				      responseReader.close();
				      System.out.println(sb.toString());
					
				} catch (Exception e1) {
					e1.printStackTrace();
				}
			} else {
				System.out.println("error++");
				
			}

		} catch (Exception e) {

		}
		
		return sb.toString();

	}
	public static void main(String[] args) {
		JSONObject jsonParam = new JSONObject();
		jsonParam.put("id", "1401_1406");
		jsonParam.put("device_size", "480x720");
		String url="www.baidu.com";
		String data=GetJsonData.getJsonData(jsonParam,url);
                //返回的是一个[{}]格式的字符串时:                               
                JSONArray jsonArray = new JSONArray(data);                       
               //返回的是一个{}格式的字符串时:                       
               /*JSONObject obj= new JSONObject(data);*/      
    }
}