HttpURLConnection简单用法-java模拟HTTP请求

HttpURLConnection为javaAPI提供的一种Rest访问的方式。其支持对Post,Delete,Get,Put等方式的访问。

以下为对于HttpURLConnection对Post等方式访问的一段代码。

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  package com.jago.cdn.util;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.HashMap;
import java.util.Map;

public class URLConnectionUtil {
   
     private static final String SERVLET_POST = "POST" ;
     private static final String SERVLET_GET = "GET" ;
     private static final String SERVLET_DELETE = "DELETE" ;
     private static final String SERVLET_PUT = "PUT" ;
    
     private static String prepareParam(Map<String,Object> paramMap){
         StringBuffer sb = new StringBuffer();
         if(paramMap.isEmpty()){
             return "" ;
         }else{
             for(String key: paramMap.keySet()){
                 String value = (String)paramMap.get(key);
                 if(sb.length()<1){
                     sb.append(key).append("=").append(value);
                 }else{
                     sb.append("&").append(key).append("=").append(value);
                 }
             }
             return sb.toString();
         }
     }
    
     public static void  doPost(String urlStr,Map<String,Object> paramMap ) throws Exception{
         URL url = new URL(urlStr);
         HttpURLConnection conn = (HttpURLConnection)url.openConnection();
         conn.setRequestMethod(SERVLET_POST);
         String paramStr = prepareParam(paramMap);
         conn.setDoInput(true);
         conn.setDoOutput(true);
         OutputStream os = conn.getOutputStream();    
         os.write(paramStr.toString().getBytes("utf-8"));    
         os.close();        
        
         BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream()));
         String line ;
         String result ="";
         while( (line =br.readLine()) != null ){
             result += "/n"+line;
         }
         System.out.println(result);
         br.close();
        
     }
    
     public static void  doGet(String urlStr,Map<String,Object> paramMap ) throws Exception{
         String paramStr = prepareParam(paramMap);
         if(paramStr == null || paramStr.trim().length()<1){
            
         }else{
             urlStr +="?"+paramStr;
         }
         System.out.println(urlStr);
         URL url = new URL(urlStr);
         HttpURLConnection conn = (HttpURLConnection)url.openConnection();
         conn.setRequestMethod(SERVLET_GET);
         conn.setRequestProperty("Content-Type","text/html; charset=UTF-8");
        
         conn.connect();
         BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream()));
         String line ;
         String result ="";
         while( (line =br.readLine()) != null ){
             result += "/n"+line;
         }
         System.out.println(result);
         br.close();
     }
    
     public static void doPut(String urlStr,Map<String,Object> paramMap) throws Exception{
         URL url = new URL(urlStr);
         HttpURLConnection conn = (HttpURLConnection)url.openConnection();
         conn.setRequestMethod(SERVLET_PUT);
         String paramStr = prepareParam(paramMap);
         conn.setDoInput(true);
         conn.setDoOutput(true);
         OutputStream os = conn.getOutputStream();    
         os.write(paramStr.toString().getBytes("utf-8"));    
         os.close();        
        
         BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream()));
         String line ;
         String result ="";
         while( (line =br.readLine()) != null ){
             result += "/n"+line;
         }
         System.out.println(result);
         br.close();
                
     }
    
     public static void doDelete(String urlStr,Map<String,Object> paramMap) throws Exception{
         String paramStr = prepareParam(paramMap);
         if(paramStr == null || paramStr.trim().length()<1){
            
         }else{
             urlStr +="?"+paramStr;
         }  
         System.out.println(urlStr);
         URL url = new URL(urlStr);
         HttpURLConnection conn = (HttpURLConnection)url.openConnection();
         conn.setDoOutput(true);
         conn.setRequestMethod(SERVLET_DELETE);
         if(conn.getResponseCode() ==200){
             System.out.println("成功");
         }else{
             System.out.println(conn.getResponseCode());
         }
     }
    
     public static void main(String[] args) throws Exception{
         String urlStr = "http://localhost:8080/SwTest/ReceiveDataServlet";
         Map<String,Object> map = new HashMap<String,Object>();
         map.put("username","张三");
         map.put("password","88888");
 //      URLConnectionUtil.doGet(urlStr, map);
 //      URLConnectionUtil.doPost(urlStr, map);
 //      URLConnectionUtil.doPut(urlStr, map);
         URLConnectionUtil.doDelete(urlStr, map);
        
     }
    
    
 }

方法中是存在重复的。有些方法是可以通过参数的改变来达到统一，但是那样的做法对于程序的扩展性会有很大的局限性。

还是对于每一种方式提供一个单独的方法进行访问比较好。

在Servlet端，获取参数可以通过

request.getInputStream,及request.getParamter来进行。

其中，当Rest访问传入参数是通过conn的outputStream来进行的，可以通过request.getInputStream来进行参数获取（Post方式可通用）；

当以url?key=value方法传递参数时，可以通过request.getParamter来进行参数获取。（Post方式可通用）

其中request.getInputStream和request.getParamter两种方式不能同时出现。当 request.getParamter运行的过程，也是输入流的读取过程。当输入流读取完成后，再次调用时无效的。

附上Servlet端程序

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   1. package com.sw.servlet;
   2. 
   3. import java.io.BufferedReader;
   4. import java.io.IOException;
   5. import java.io.InputStreamReader;
   6. import java.io.OutputStream;
   7. 
   8. import javax.servlet.ServletException;
   9. import javax.servlet.ServletInputStream;
  10. import javax.servlet.http.HttpServlet;
  11. import javax.servlet.http.HttpServletRequest;
  12. import javax.servlet.http.HttpServletResponse;
  13. 
  14. /**
  15.  * Servlet implementation class ReceiveDataServlet
  16.  */
  17. public class ReceiveDataServlet extends HttpServlet {
  18.     private static final long serialVersionUID = 1L;
  19.        
  20.     /**
  21.      * @see HttpServlet#HttpServlet()
  22.      */
  23.     public ReceiveDataServlet() {
  24.         super();
  25.         // TODO Auto-generated constructor stub
  26.     }
  27. 
  28.     /**
  29.      * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
  30.      */
  31.     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  32.         System.out.println("----------get--------------");      
  33.         String username = new String(request.getParameter("username").getBytes("iso-8859-1"),"utf-8");
  34.         String password = new String(request.getParameter("password").getBytes("iso-8859-1"),"utf-8");
  35.         System.out.println(username);
  36.         System.out.println(password);
  37.         OutputStream os = response.getOutputStream();
  38.         os.write("get".getBytes("utf-8"));
  39.     }
  40. 
  41.     /**
  42.      * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
  43.      */
  44.     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  45.         System.out.println("----------post--------------");
  46.         BufferedReader br = new BufferedReader(new InputStreamReader((ServletInputStream)request.getInputStream()));
  47.         String line = null;
  48.         StringBuilder sb = new StringBuilder();
  49.         while((line = br.readLine())!=null){
  50.             sb.append(line);
  51.         }       
  52.         System.out.println(sb.toString());
  53.         br.close();
  54. /*      String username = new String(request.getParameter("username").getBytes("iso-8859-1"),"utf-8");
  55.         String password = new String(request.getParameter("password").getBytes("iso-8859-1"),"utf-8");
  56.         System.out.println(username);
  57.         System.out.println(password);
  58. */      OutputStream os = response.getOutputStream();
  59.         os.write("post".getBytes("utf-8"));
  60.     }
  61.     
  62.     @Override
  63.     protected void doDelete(HttpServletRequest request, HttpServletResponse response)
  64.             throws ServletException, IOException {
  65.         System.out.println("----------delete--------------");
  66.         String username = new String(request.getParameter("username").getBytes("iso-8859-1"),"utf-8");
  67.         String password = new String(request.getParameter("password").getBytes("iso-8859-1"),"utf-8");
  68.         System.out.println(username);
  69.         System.out.println(password);
  70.         OutputStream os = response.getOutputStream();
  71.         os.write("delete".getBytes("utf-8"));           
  72.     }
  73.     
  74.     @Override
  75.     protected void doPut(HttpServletRequest request, HttpServletResponse response)
  76.             throws ServletException, IOException {
  77.         System.out.println("----------put--------------");
  78.         
  79.     /*  BufferedReader br = new BufferedReader(new InputStreamReader((ServletInputStream)request.getInputStream()));
  80.         String line = null;
  81.         StringBuilder sb = new StringBuilder();
  82.         while((line = br.readLine())!=null){
  83.             sb.append(line);
  84.         }      
  85.         System.out.println(sb.toString());
  86.         br.close();*/
  87.         
  88.         String username = new String(request.getParameter("username").getBytes("iso-8859-1"),"utf-8");
  89.         String password = new String(request.getParameter("password").getBytes("iso-8859-1"),"utf-8");
  90.         System.out.println(username);
  91.         System.out.println(password);
  92.         OutputStream os = response.getOutputStream();
  93.         os.write("put".getBytes("utf-8"));  
  94.     }
  95. 
  96. }

程序中对于request.getInputStream和getParameter的获取方式可能说明的会多少有些问题，我也是通过几组测试后得出的结论。肯定有我没有测试到得。如果有问题，请指出，我会再看到评论后进行测试，修改。

另外，Apache的HttpClient非常好。封装的详细。在我的工作中也用到过，在以后会对于HttpClient进行有些单独的程序笔记。

这里HttpUrlConnection是同事在别的项目中用到的，用法比较简单，我大体给他简单讲解了一下，简明扼要，功能完备，还是很方便，

所以在这里记下来，留个笔记吧。

btw,最近工作比较忙，有2个月没有写些东西了，在工作中确实还遇到了不少有意思的问题，最近刚好快闲下来了，慢慢整理一下。