javaWeb页面验证码的生成

下面是验证码生成的基本步骤和源码，如果有什么不足的请指出

首先设计jsp页面，Login.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>








	用户名：

	密码：

	验证码：
	
	
	
${requestScope.info }

其次设计验证码生成的servlet，CheckCode.java

package servlet;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.IOException;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

/**
 * Servlet implementation class CheckCode
 */
@WebServlet("/CheckCode")
public class CheckCode extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public CheckCode() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
//		response.getWriter().append("Served at: ").append(request.getContextPath());
		response.setContentType("image/jpeg");
		HttpSession session = request.getSession();
		int width = 60;
		int height = 20;
		
		// Set the browser not to cache the picture
		response.setHeader("Pragma", "N0-cache");
		response.setHeader("Cache-Control", "no-cache");
		response.setDateHeader("Expires", 0);
		
		// Create a memory image and get its context
		BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
		Graphics g = image.getGraphics();
		
		// Generating Random Verification Codes
		// Character table defining validation codes
		String chars = "0123456789ABCDEFGHIGKLMNOPQRSTUVWXYZ";
		char[] rands = new char[4];
		for(int i=0;i<4;i++) {
			int rand = (int)(Math.random()*36);
			rands[i] = chars.charAt(rand);
		}
		
		// generating image
		// draw background
		g.setColor(new Color(0xDCDCDC));
		g.fillRect(0, 0, width, height);
		
		// Random generation of 120 interference points
		for(int i=0;i<120;i++) {
			int x = (int)(Math.random()*width);
			int y = (int)(Math.random()*height);
			int red = (int)(Math.random()*255);
			int green = (int)(Math.random()*255);
			int blue = (int)(Math.random()*255);
			g.setColor(new Color(red,green,blue));
			g.drawOval(x, y, 1, 0);
		}
		g.setColor(Color.black);
		g.setFont(new Font(null,Font.ITALIC|Font.BOLD,18));
		
		// Output different characters of verification code at different heights
		g.drawString(""+rands[0], 1, 17);
		g.drawString(""+rands[1], 16, 15);
		g.drawString(""+rands[2], 31, 18);
		g.drawString(""+rands[3], 46, 16);
		g.dispose();
		
		// output the image to client
		ServletOutputStream sos = response.getOutputStream();
		ByteArrayOutputStream baos = new ByteArrayOutputStream();
		ImageIO.write(image,"JPEG",baos);
		byte[] buffer = baos.toByteArray();
		response.setContentLength(buffer.length);
		sos.write(buffer);
		baos.close();
		sos.close();
		
		// Put the validation code into session
		session.setAttribute("checkCode", new String(rands));
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

设计更换验证码的servlet，ChangeCheckCode.java

package servlet;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class ChangeCheckCode
 */
@WebServlet("/ChangeCheckCode")
public class ChangeCheckCode extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public ChangeCheckCode() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		response.getWriter().append("Served at: ").append(request.getContextPath());
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
//		doGet(request, response);
		request.setCharacterEncoding("utf-8");
		response.setContentType("html/text;character=utf-8");
		request.getRequestDispatcher("/Login.jsp").forward(request, response);
	}

}

最后设计登陆验证的servlet，LogCheck.java

package servlet;

import java.io.IOException;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

/**
 * Servlet implementation class LogCheck
 */
@WebServlet("/LogCheck")
public class LogCheck extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public LogCheck() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		response.getWriter().append("Served at: ").append(request.getContextPath());
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
//		doGet(request, response);
		request.setCharacterEncoding("utf-8");
		String userid = request.getParameter("userid");
		String userpwd = request.getParameter("userpwd");
		String usercheckcode = request.getParameter("checkcode");
		String info = "";
		HttpSession session = request.getSession();
		String servercheckcode = (String)session.getAttribute("checkCode");
		if(!servercheckcode.equalsIgnoreCase(usercheckcode)) {
			info = "验证码不正确，请重新输入";
		}else if("张三".equals(userid)&&"123".equals(userpwd)){
			info = "登陆成功";
		}else {
			info = "用户名或者密码不正确";
		}
		request.setAttribute("info", info);
		RequestDispatcher rd = request.getRequestDispatcher("/Login.jsp");
		rd.forward(request, response);
	}

}