原生Java发送Post请求

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStreamWriter;
import java.net.HttpURLConnection;
import java.net.URL;
import java.io.BufferedReader;
import java.io.InputStreamReader;

public class JavaPostJson2 {
    final static String url = "http://localhost:1111/sendData";
    // final static String params = "{\"token\":\"12345\","
    //         + "\"appId\":\"20180628173051169c85d965d164ed9ab1281d22ff350ec19\"" 
    //         + "\"appName\":\"test33\""
    //         + "\"classTopic\":\"112\"" 
    //         + "\"eventTag\":\"22\"" 
    //         + "\"msg\":{}"
    //         + "}";
    final static String params = "{\"token\":\"12345\","
            + "\"appId\":\"20180628173051169c85d965d164ed9ab1281d22ff350ec19\","
            + "\"appName\":\"test33\","
            + "\"classTopic\":\"112\","
            + "\"eventTag\":\"22\""
            + "}";

    public static void main(String[] args) {

        String res = post(url, params);
        System.out.println(res);

    }

    /**
     * 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);
        BufferedReader reader = null;
        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
            reader = new BufferedReader(new InputStreamReader(connection.getInputStream(), "UTF-8"));
            String line;
            String res = "";
            while ((line = reader.readLine()) != null) {
                res += line;
            }
            reader.close();

            return res;
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return "error"; // 自定义错误信息
    }

}