Java 实现 Http 请求工具类

 package com.demo.util;

 import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStreamReader;
 import java.io.OutputStreamWriter;
 import java.net.URL;
 import java.net.URLConnection;

 public class HttpUtil {
     /**
      * 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 result     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 param      请求参数，请求参数应该是 name1=value1&name2=value2 的形式。
      * @return result    所代表远程资源的响应结果
      */
     public static String sendPost(String url, String param) {
         OutputStreamWriter 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)");
             conn.setRequestProperty("Charset", "utf-8");
             //发送POST请求必须设置如下两行
             conn.setDoOutput(true);
             conn.setDoInput(true);
             //获取URLConnection对象对应的输出流
             out = new OutputStreamWriter(conn.getOutputStream(), "utf-8");//这里设定需要字符集，防止项目环境编码与URL地址环境的编码（UTF-8）不一样，造成响应结果乱码
             // 发送请求参数
             out.write(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(),"utf-8"));
             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;
     }    

 }