java 自带 http get/post 请求

请求参数，请求参数应该是 name1=value1&name2=value2 的形式。

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.URL;
import java.net.URLConnection;
import java.util.List;
import java.util.Map;
import java.util.Set;

public class HttpRequest {
    /**
     * 向指定URL发送GET方法的请求
     * 
     * @param url   发送请求的URL
     * @param param 请求参数，请求参数应该是 name1=value1&name2=value2 的形式。
     * @return URL 所代表远程资源的响应结果
     */
    public static String sendGet(String url, String param) {
        String result = "";
        BufferedReader in = null;
        try {
            String urlNameString = url + "?" + param;
            URL realUrl = new URL(urlNameString);
            // 打开和URL之间的连接
            URLConnection connection = realUrl.openConnection();
            // 设置通用的请求属性
            connection.setRequestProperty("accept", "*/*");
            connection.setRequestProperty("connection", "Keep-Alive");
            connection.setRequestProperty("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
            // 建立实际的连接
            connection.connect();
            // 获取所有响应头字段
            Map<String, List<String>> map = connection.getHeaderFields();
            // 遍历所有的响应头字段
            for (String key : map.keySet()) {
                System.out.println(key + "--->" + map.get(key));
            }
            // 定义 BufferedReader输入流来读取URL的响应
            in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
            String line;
            while ((line = in.readLine()) != null) {
                result += line;
            }
        } catch (Exception e) {
            System.out.println("发送GET请求出现异常！" + e);
            e.printStackTrace();
        }
        // 使用finally块来关闭输入流
        finally {
            try {
                if (in != null) {
                    in.close();
                }
            } catch (Exception e2) {
                e2.printStackTrace();
            }
        }
        return result;
    }

    /**
     * 向指定 URL 发送POST方法的请求
     * 
     * @param url 发送请求的 URL
     * @param map/param 请求参数
     *               
     * 请求参数，请求参数应该是 name1=value1&name2=value2 的形式。
     * @return 所代表远程资源的响应结果
     */
    public static String sendPost(String url, String param) {
//    public static String sendPost(String url, Map<String, String> map) {
//        String param = getKeyVAlueSting(map);    //如果是参数是String 就不需要再转换成name1=value1&name2=value2 的形式
        System.out.println(param);
        PrintWriter out = null;
        BufferedReader in = null;
        String result = "";
        try {
            URL realUrl = new URL(url);
            // 打开和URL之间的连接
            URLConnection conn = realUrl.openConnection();
            // 设置通用的请求属性
            conn.setRequestProperty("accept", "*/*");
            conn.setRequestProperty("connection", "Keep-Alive");
            conn.setRequestProperty("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
            // 发送POST请求必须设置如下两行
            conn.setDoOutput(true);
            conn.setDoInput(true);
            // 1.获取URLConnection对象对应的输出流
            out = new PrintWriter(conn.getOutputStream());
            // 2.中文有乱码的需要将PrintWriter改为如下
            // out=new OutputStreamWriter(conn.getOutputStream(),"UTF-8")
            // 发送请求参数
            out.print(param);
            // flush输出流的缓冲
            out.flush();
            // 定义BufferedReader输入流来读取URL的响应
            in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
            String line;
            while ((line = in.readLine()) != null) {
                result += line;
            }
        } catch (Exception e) {
            System.out.println("发送 POST 请求出现异常！" + e);
            e.printStackTrace();
        }
        // 使用finally块来关闭输出流、输入流
        finally {
            try {
                if (out != null) {
                    out.close();
                }
                if (in != null) {
                    in.close();
                }
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }
        return result;
    }

    /**
     * 获取key=value格式字符串
     *
     * @param map
     * @return
     */
    public static String getKeyVAlueSting(Map<String, String> map) {
        String sign = "";

        Set<String> set = map.keySet();
        for (String key : set) {
            sign += key + "=" + map.get(key) + "&";
        }

        sign = sign.substring(0, sign.length() - 1);

        return sign;
    }

    public static void main(String[] args) {
        HttpRequest httpRequest = new HttpRequest();

//测试微信项目中通过post请求获取access token
        String url = "https://api.weixin.qq.com/cgi-bin/token";
        String param = "grant_type=client_credential&appid=wxfc27805daac56d9b&secret=12d853529003c68d0d2c9d4f87dd8b57";
        String sr=HttpRequest.sendPost(url, param);
        System.out.println(sr);
    }
}

Json格式、Post请求：

    /**Map转json post请求*/
    public void a(){
        Map<String, String> map = new LinkedHashMap<>();
        map.put("type",type)
        Map<String, String> requestMap = new LinkedHashMap<>();
        requestMap.put("bg_url", bg_url);
        requestMap.put("biz_code", biz_code);
        requestMap.put("sign", sign);
        map.put("data",requestMap);
        // 组装请求参数,JSON格式
        JSONObject json = new JSONObject(map);

        String result=sendPostJson("请求地址url",json.toJSONString());
    }

    /**
     * Post请求、 Json格式
     * @param strURL
     * @param params
     * @return
     */
    public static String sendPostJson(String strURL, String 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("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 ""; // 自定义错误信息
    }