javascript实现网页登录验证码

SeccodeServlet.java

package servlet;

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

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

public class SeccodeServlet extends HttpServlet {
	private static final int width = 200;
	private static final int height = 50;
	private static final String code = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ123456789";
	private Random random = new Random();
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.setContentType("image/jpeg");
		BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_BGR);
		Graphics g = image.getGraphics();
		g.setColor(getColor(200,40));
		g.fillRect(0,0,width,height);
		
		for(int i=0;i<100;i++){
			int x1 = random.nextInt(width);
			int y1 = random.nextInt(width);
			int x2 = random.nextInt(width);
			int y2 = random.nextInt(width);
			g.setColor(getColor(160,40));
			g.drawLine(x1, y1, x2, y2);
			
		}
		//输出字符
		String seccode = "";
		Font font = new Font("宋体",Font.ITALIC,width/4);
		g.setFont(font);
		for(int i=0;i<4;i++){
			char c = code.charAt(random.nextInt(code.length()));
			seccode += c;
			g.setColor(getColor(100,40));
			g.drawString(c + "", i*width/4 + 5, 40);
		}
		HttpSession sessino = request.getSession();
		sessino.setAttribute("seccode",seccode);
		
		ImageIO.write(image, "JPEG", response.getOutputStream());
		g.dispose();
		
		
		
		
		ImageIO.write(image, "JPEG", response.getOutputStream());
		g.dispose();
	}
	private Color getColor(int base,int inc){
		int r = base + random.nextInt(inc);
		int g = base + random.nextInt(inc);
		int b = base + random.nextInt(inc);
		return new Color(r,g,b);
		
	}

}

login.jsp

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



  
    
    
    
	
	
	    
	
	
	
  
  
  
    <%
    String msg=(String) session.getAttribute("msg");
    if(msg!=null){
    	session.removeAttribute("msg");
    	out.println("" +msg+"");
    }
    %>
    

    用户名：

    用户名：

    验证码：

    
        /seccode"/>

        
        
    
    
    
  

web.xml

  
    This is the description of my J2EE component
    This is the display name of my J2EE component
    SeccodeServlet
    servlet.SeccodeServlet
  
  
    This is the description of my J2EE component
    This is the display name of my J2EE component
    LoginServlet
    servlet.LoginServlet
  


  
    SeccodeServlet
    /seccode
  
  
    LoginServlet
    /login
  
  
    index.jsp
  

LoginServlet.java

package servlet;

import java.io.IOException;
import java.io.PrintWriter;

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

public class LoginServlet extends HttpServlet {

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		request.setCharacterEncoding("UTF-8");
		response.setContentType("text/html;charset=utf-8");
		PrintWriter out = response.getWriter();
		
		String secode = request.getParameter("seccode");
		
		HttpSession session = request.getSession();
		String oldCode=(String)session.getAttribute("seccode");
		if(!secode.equals(oldCode)){
			session.setAttribute("msg","验证码不正确！！");
			response.sendRedirect("login.jsp");
		}else{
			out.println("验证码输入正确");
		}

		out.flush();
		out.close();
	}

}