java验证码

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.ServletOutputStream;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpSession;

public class ValidateCodeServlet extends HttpServlet {

 

    protected void processRequest(HttpServletRequest request, HttpServletResponse response)

    throws ServletException, IOException {

        response.setContentType("image/jpeg");

        response.setHeader("Pragma","No-cache");

        response.setHeader("Cache-Control","no-cache");

        response.setDateHeader("Expires", 0);      

        HttpSession session=request.getSession();

        // 在内存中创建图象

        int width=60, height=20;

        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

        // 获取图形上下文

        Graphics g = image.getGraphics();

        //生成随机类

        Random random = new Random();

        // 设定背景色

        g.setColor(getRandColor(200,250));

        g.fillRect(0, 0, width, height);

        //设定字体

        g.setFont(new Font("Times New Roman",Font.PLAIN,18));

        //画边框

        //g.setColor(new Color());

        //g.drawRect(0,0,width-1,height-1);

 

        // 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到

        g.setColor(getRandColor(160,200));

        for (int i=0;i<155;i++) {

            int x = random.nextInt(width);

            int y = random.nextInt(height);

            int xl = random.nextInt(12);

            int yl = random.nextInt(12);

            g.drawLine(x,y,x+xl,y+yl);

        }

        // 取随机产生的认证码(4位数字)

        String sRand="";

        for (int i=0;i<4;i++){

            String rand=String.valueOf(random.nextInt(10));

            sRand+=rand;

            // 将认证码显示到图象中

            g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));//调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成

            g.drawString(rand,13*i+6,16);

        }

        // 将认证码存入SESSION

        session.setAttribute("rand",sRand);

        // 图象生效

        g.dispose();

        ServletOutputStream responseOutputStream =response.getOutputStream();

        // 输出图象到页面

        ImageIO.write(image, "JPEG", responseOutputStream);

        //以下关闭输入流！

        responseOutputStream.flush();

        responseOutputStream.close();

    }

    Color getRandColor(int fc,int bc){//给定范围获得随机颜色

        Random random = new Random();

        if(fc>255) fc=255;

        if(bc>255) bc=255;

        int r=fc+random.nextInt(bc-fc);

        int g=fc+random.nextInt(bc-fc);

        int b=fc+random.nextInt(bc-fc);

        return new Color(r,g,b);

    }

    // <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">

   

    protected void doGet(HttpServletRequest request, HttpServletResponse response)

    throws ServletException, IOException {

        processRequest(request, response);

    }

   

    protected void doPost(HttpServletRequest request, HttpServletResponse response)

    throws ServletException, IOException {

        processRequest(request, response);

    }

   

    public String getServletInfo() {

        return "Short description";

    }

    // </editor-fold>

 

 

    }