图片验证码

1.今天从网上找了一个图片验证码的例子，很好，看代码

package com.zhao.util;

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 AuthImg extends HttpServlet
{
    private Font mFont = new Font("Arial Black", Font.BOLD, 16);//字体，风格，字号
    public void init() throws ServletException
    {
        super.init();//applet初始化，在applet首次创建时执行
    }
    Color getRandColor(int fc,int bc)//随机产生r,g,b均在fc和bc之间的一种颜色
    {
        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);
    }

    public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
    {
        response.setHeader("Pragma","No-cache");
        response.setHeader("Cache-Control","no-cache");
        response.setDateHeader("Expires", 0);
        response.setContentType("image/jpeg");
        
        int width=100, height=150;
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_4BYTE_ABGR);
        
        Graphics g = image.getGraphics();
        Random random = new Random();
        g.setColor(getRandColor(200,250));
        g.fillRect(1, 1, width-1, height-1);
        g.setColor(new Color(102,102,102));
        g.drawRect(0, 0, width-1, height-1);//画矩形。左角坐标，宽，高
        g.setFont(mFont);

        g.setColor(getRandColor(160,200));
        for (int i=0;i<155;i++)
        {
            int x = random.nextInt(width - 1);
            int y = random.nextInt(height - 1);
            int xl = random.nextInt(6) + 1;
            int yl = random.nextInt(12) + 1;
            g.drawLine(x,y,x + xl,y + yl);//画直线起点坐标、终点坐标
        }
        for (int i = 0;i < 70;i++)
        {
            int x = random.nextInt(width - 1);
            int y = random.nextInt(height - 1);
            int xl = random.nextInt(12) + 1;
            int yl = random.nextInt(6) + 1;
            g.drawLine(x,y,x - xl,y - yl);
        }

        String sRand="";
        for (int i=0;i<6;i++)
        {
			String tmp = getRandomChar();
            sRand += tmp;
            g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));
	        g.drawString(tmp,15*i+10,15);//写文本tmp
        }

        HttpSession session = request.getSession(true);
        session.setAttribute("rand",sRand);
        g.dispose();
        ImageIO.write(image, "JPEG", response.getOutputStream());
    }
    private String getRandomChar()//产生文本
    {
		int rand = (int)Math.round(Math.random() * 2);
		long itmp = 0;
		char ctmp = '\u0000';
		switch (rand)
		{
			case 1:
				itmp = Math.round(Math.random() * 25 + 65);
				ctmp = (char)itmp;
				return String.valueOf(ctmp);
			case 2:
				itmp = Math.round(Math.random() * 25 + 97);
				ctmp = (char)itmp;
				return String.valueOf(ctmp);
			default :
				itmp = Math.round(Math.random() * 9);
				return String.valueOf(itmp);
		}
    }
}

2.原作者给的步骤

1.建立一个AuthImg类，用来生成验证码
2.在web中配置AuthImg
  <servlet>
    <servlet-name>img</servlet-name>
    <servlet-class>com.zhao.util.AuthImg</class-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>img</servlet-name>
    <url-pattern>/authImg</url-pattern>
  </servlet-mapping>
3.页面上：
 验证码如图：<img src="authImg" id="authImg"/>看不清？<a href="#" onClick="refresh()">单击此处刷新</a>
<SCRIPT type="text/javascript" >
			function refresh(){
				document.getElementById("authImg").src='authImg?now='+new Date();
			}
		</SCRIPT>
4.AuthImg.java

3.截图（框框改的有点大）