http接口调用POST--参数json格式

package user;

/**
 * Created by www on 17/6/12.
 */

import org.json.JSONObject;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStreamWriter;
import java.net.HttpURLConnection;
import java.net.URL;
//success
public class postN {

    final static String url = "http://www.test/api/queryCouponById";
    final static String params = "{\"id\":\"1\"}";

    /**
     * 发送HttpPost请求
     *
     * @param strURL
     *            服务地址
     * @param params
     *            json字符串,例如: "{ \"id\":\"12345\" }" ;其中属性名必须带双引号<br/>
     * @return 成功:返回json字符串<br/>
     */
    public static String post(String strURL, String params) {

        System.out.println(strURL);
        System.out.println(params);
        try {
            URL url = new URL(strURL);// 创建连接
            HttpURLConnection connection = (HttpURLConnection) url
                    .openConnection();
            connection.setDoOutput(true);
            connection.setDoInput(true);
            connection.setUseCaches(false);
            connection.setInstanceFollowRedirects(true);
            connection.setRequestMethod("POST"); // 设置请求方式
            connection.setRequestProperty("Accept", "application/json"); // 设置接收数据的格式
            connection.setRequestProperty("Content-Type", "application/json"); // 设置发送数据的格式
            connection.connect();
            OutputStreamWriter out = new OutputStreamWriter(
                    connection.getOutputStream(), "UTF-8"); // utf-8编码
            out.append(params);
            out.flush();
            out.close();
            // 读取响应
            int length = (int) connection.getContentLength();// 获取长度
            InputStream is = connection.getInputStream();
            if (length != -1) {
                byte[] data = new byte[length];
                byte[] temp = new byte[512];
                int readLen = 0;
                int destPos = 0;
                while ((readLen = is.read(temp)) > 0) {
                    System.arraycopy(temp, 0, data, destPos, readLen);
                    destPos += readLen;
                }
                String result = new String(data, "UTF-8"); // utf-8编码
                System.out.println(result);
                return result;
            }
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return "error"; // 自定义错误信息
    }

    public static void main(String[] args) {

        post(url, params);
    }

}
____________________________________________________________
对应maven 

<!--json包 -->
<dependency>
    <groupId>net.sf.json-lib</groupId>
    <artifactId>json-lib</artifactId>
    <version>2.4</version>
    <classifier>jdk15</classifier>
</dependency>
<!--json包-->
<dependency>
    <groupId>org.json</groupId>
    <artifactId>json</artifactId>
    <version>20150729</version>
</dependency>