自定义URL请求工具类: get请求以及带json参数的post请求

package com.fengche.utils;

import com.google.gson.Gson;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.HashMap;
import java.util.Map;

/**
 * Created by Administrator on  2018/9/5
 */
public class URLUtils {

    /**
     * Get请求
     *
     * @param url
     * @return
     */
    public static String sendGet(String url) {
        try {
            URL u = new URL(url);
            String res = inputStreamToString(u.openStream());
            return res;
        } catch (Exception e) {
            System.out.println(url + "：get请求出错");
            e.printStackTrace();
            return null;
        }
    }

    /**
     * Post请求
     *
     * @param url
     * @return
     */
    public static String sendPost(String url) {
        try {
            URL u = new URL(url);
            HttpURLConnection con = (HttpURLConnection) u.openConnection();
            con.setRequestMethod("POST");
            String res = inputStreamToString(con.getInputStream());
            return res;
        } catch (Exception e) {
            System.out.println(url + "：post请求出错");
            e.printStackTrace();
            return null;
        }
    }

    /**
     * Post请求，json传参
     *
     * @param url
     * @param params
     * @return
     */
    public static String sendPost(String url, Map<String, Object> params) {
        try {
            URL u = new URL(url);
            HttpURLConnection con = (HttpURLConnection) u.openConnection();

            con.setRequestMethod("POST");
            //flag to true if you intend to use the URL connection for output.The default is false.
            //要在请求体中传参，必须开启这个属性。默认为false
            con.setDoOutput(true);
            //设置参数形式为json
            con.setRequestProperty("Content-Type", "application/json");
            //传参
            if (params.size() > 0) {
                OutputStream out = con.getOutputStream();
                out.write(new Gson().toJson(params).getBytes());
                out.flush();
                out.close();
            }
            //查看状态码
            String res = inputStreamToString(con.getInputStream());
            return res;
        } catch (Exception e) {
            System.out.println(url + "：post请求出错");
            e.printStackTrace();
            return null;
        }
    }

    /**
     * InputStream 转 String
     *
     * @param InputStream
     * @return String
     */
    public static String inputStreamToString(InputStream inputStream) throws IOException {
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        byte buf[] = new byte[1024];
        int read = 0;
        while ((read = inputStream.read(buf)) > 0) {
            out.write(buf, 0, read);
        }
        //可设置gbk编码
        String res = new String(out.toByteArray(), "utf-8");
        out.close();
        return res;
    }

    /**
     * 测试
     * @param args
     */
    public static void main(String[] args) {
        String sb = "name";
        Map<String,Object> params = new HashMap<>();
        params.put("name","huang");
        params.put("date","2018年9月5日");
        String res = sendPost("http://localhost/info/post",params);
        System.out.println(res);
    }
}