转载:通过Servlet生成验证码

package servlet;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
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;

/**
 * 生成随机图片，用来作为验证码
 */
public class DrawImage extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    public static final int WIDTH = 120;//生成图片的宽度
    public static final int HEIGHT = 30;//生成图片的高度 
    public DrawImage() {
        super();
        // TODO Auto-generated constructor stub
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }


    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //接收客户端传递的createTypeFlag标识
        String createTypeFlag = request.getParameter("createTypeFlag");
        //1.在内存中生成图片
        BufferedImage image = new BufferedImage(WIDTH,HEIGHT,BufferedImage.TYPE_INT_RGB);
        //2.获得图片
        Graphics g = image.getGraphics();
        //3.设置图片的背景颜色
        setBackground(g);
        //4.设置图片的边框
        setBorder(g);
        //5.在图片上画干扰线
        drawRandomLine(g);
        //6.在图片上写随机数
        String random = drawRandomNum((Graphics2D)g,createTypeFlag);//根据客户端传递的createTypeFlag标识生成验证码图片
        //7.将随机数存在session中
        request.getSession().setAttribute("checkcode", random);
        //8.设置响应头通知浏览器以图片的形式打开
        response.setHeader("content-type", "image/jpeg");
        //9.设置响应头控制浏览器不要缓存
        response.setDateHeader("expires", -1);
        response.setHeader("Cache-Control", "no-cache");
        response.setHeader("Pragma", "no-cache");
        //10.将图片写给浏览器
        ImageIO.write(image, "jpg", response.getOutputStream());
    }
    
    /**
     * 设置图片背景颜色
     * @param g
     */
    private void setBackground(Graphics g){
        //设置颜色
        g.setColor(Color.WHITE);
        //填充区域
        g.fillRect(0, 0, WIDTH, HEIGHT);
    }
    
    /**
     * 设置图片的边框
     * @param g
     */
    private void setBorder(Graphics g){
        //设置边框颜色
        g.setColor(Color.BLUE);
        //边框区域
        g.drawRect(1, 1, WIDTH - 2, HEIGHT - 2);
    }
    
    /**
     * 设置干扰线
     * @param g
     */
    private void drawRandomLine(Graphics g){
        //设置颜色
        g.setColor(Color.GREEN);
        //设置线条个数并画线
        for(int i = 0; i < 5; i++){
            int x1 = new Random().nextInt(WIDTH);
            int y1 = new Random().nextInt(HEIGHT);
            int x2 = new Random().nextInt(WIDTH);
            int y2 = new Random().nextInt(HEIGHT);
            g.drawLine(x1, y1, x2, y2);
        }
    }
    
    private String drawRandomNum(Graphics2D g,String...createTypeFlag){
        //设置颜色
        g.setColor(Color.red);
        //设置字体
        g.setFont(new Font("宋体",Font.BOLD,20));
        //常用的中国汉字
        String baseChineseChar = 
                "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";
        //数字和字母的组合
        String baseNumLetter = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
        //纯数字
        String baseNum = "0123456789";
        //纯字母
        String baseLetter = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
        //createTypeFlag[0]==null表示没有传递参数
        if(createTypeFlag.length > 0 && createTypeFlag[0] != null){
            if(createTypeFlag[0].equals("ch")){
                //截取汉字
                return createRandomChar(g,baseChineseChar);
            }else if(createTypeFlag[0].equals("nl")){
                //截取数字和字母的组合
                return createRandomChar(g,baseNumLetter);
            }else if(createTypeFlag[0].equals("n")){
                //截取数字
                return createRandomChar(g,baseNum);
            }else if(createTypeFlag[0].equals("l")){
                //截取字母
                return createRandomChar(g,baseLetter);
            }else{
                //默认截取数字和字母的组合
                return createRandomChar(g,baseNumLetter);
            }
        }else{
            //默认截取数字和字母的组合
            return createRandomChar(g,baseNumLetter);
        }
        
    }
    
    /**
     * 创建随机字符
     * @param g
     * @param str
     * @return
     */
    private String createRandomChar(Graphics2D g, String baseChar) {
        StringBuffer sb = new StringBuffer();
        int x = 5;
        String ch = "";
        for(int i = 0; i <4; i++){
            //设置字体旋转角度
            int degree = new Random().nextInt() % 30;
            ch = baseChar.charAt(new Random().nextInt(baseChar.length()))+"";
            sb.append(ch);
            //正向角度
            g.rotate(degree * Math.PI/180,x,20);
            g.drawString(ch, x, 20);
            //反向角度
            g.rotate(-degree * Math.PI/180, x, 20);
            x += 30;
        }
        return sb.toString();
    }
}