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;
    }    
    
}