Servlet：response生成图片验证码

src 目录下com.xieyuan包MyServlet.java文件（Servlet文件）

package com.xieyuan;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.URLEncoder;
import java.util.Random;

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.sun.corba.se.impl.javax.rmi.CORBA.Util;
import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;

public class MyServlet extends HttpServlet {

	/**
	 * Constructor of the object.
	 */
	public MyServlet() {
		super();
	}

	/**
	 * Destruction of the servlet. 

	 */
	public void destroy() {
		super.destroy(); // Just puts "destroy" string in log
		// Put your code here
	}

	/**
	 * The doGet method of the servlet. 

	 *
	 * This method is called when a form has its tag value method equals to get.
	 * 
	 * @param request the request send by the client to the server
	 * @param response the response send by the server to the client
	 * @throws ServletException if an error occurred
	 * @throws IOException if an error occurred
	 */
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		execute(request, response);
	}

	/**
	 * The doPost method of the servlet. 

	 *
	 * This method is called when a form has its tag value method equals to post.
	 * 
	 * @param request the request send by the client to the server
	 * @param response the response send by the server to the client
	 * @throws ServletException if an error occurred
	 * @throws IOException if an error occurred
	 */
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		execute(request, response);
	}

	
	private static final char CHARS[]={'2','3','4','5','6','7','8','9','A','B','C','D','E',
		                               'F','G','H','J','K','L','M','N','P','Q','R','S','T','U','V',
		                               'W','X','Y','Z'
	                                  };
	public static Random random=new Random();
	//生成随机数字，len为需要随机数字的个数
	public static String getRandomString(int len)
	{
		StringBuilder builder=new StringBuilder();
		for(int i=0;i
	 *
	 * @throws ServletException if an error occurs
	 */
	public void init() throws ServletException {
	}

}

配置好web.xml

  
    This is the description of my J2EE component
    This is the display name of my J2EE component
    MyServlet
    com.xieyuan.MyServlet
  

  
    MyServlet
    /servlet/MyServlet
  
  
    index.jsp
  

接着部署您的WEB 应用，此时访问：

http://127.0.0.1:8080/Test/servlet/MyServlet

可以看到一张图片验证码。但是，这种效果好吗？这,并不是我们想要的，图片验证码应该混搭在HTML页面里，做登录等功能才对。

那么，接下来我们来做个JSP页面，直接使用项目WebRoot目录下的，index.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>



  
    
    
    
	
	
	    
	
	
	
	
  
  
  
     


     

     
  

此时，我直接访问：http://127.0.0.1:8080/Test/  

结果就是我们想要的了

可以看到，无论我们点击多少次 “换一张图片”按钮，网页始终没有刷新，页面最后更新时间也没变，变的就是图片验证码！