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
     }