验证码生成

系统登陆或者注册的时候，为了防止恶意注册或者机器自动注册，采用验证码是常常使用的方式，下面是自己参考网上写的，自己处理了一下，目前使用的一个验证码生成类，其代码如下：

 

1、首先是验证码生成的Java类

package com.mail.sys.sysmgr.action;

import java.io.IOException;  
import javax.servlet.ServletException;  
import javax.servlet.http.HttpServlet;  
import javax.servlet.http.HttpServletRequest;  
import javax.servlet.http.HttpServletResponse;  
import javax.servlet.http.HttpSession;  
import java.util.*;  
import java.awt.*;  
import java.awt.image.*;  
  
import javax.imageio.*;  
/**
 * 登录验证码生成器
 * @author lizhenbin
 *
 */
public class RandCodeServlet extends HttpServlet {  
	
    private static final long serialVersionUID = 1L;  
  
    /** 
     * @see HttpServlet#HttpServlet() 
     */  
    public RandCodeServlet() {  
        super();  
        // TODO Auto-generated constructor stub  
    }  
    /**
     * 验证码生成方法
     */
    public void doGet(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 = 70, height = 25;  
        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, 20));  
        // 画边框  
        g.setColor(getRandColor(160, 200));  
        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 + 14, 20);  
        }  
        
        // 将认证码存入SESSION  
        session.setAttribute("vcode_sRand", sRand);  
  
        // 图象生效  
        g.dispose();  
        // 输出图象到页面  
        ImageIO.write(image, "JPEG", response.getOutputStream());  
    }  
  
    /**
     * 调用doGet
     */
    public void doPost(HttpServletRequest request,  
            HttpServletResponse response) throws ServletException, IOException {  
        // TODO Auto-generated method stub  
    	this.doGet(request, response);
    }  
  
    /**
     * 颜色产生器
     * @param fc
     * @param bc
     * @return
     */
    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);  
    }  
  
}  

 2、页面调用验证码部分

<tr>
              <td height="30"> 验 证 码: </td>
			  <td>
			  	  <input type="text" id="j_captcha_response">
			      <img src="servlet/RandCode" alt="验证码" name="checkImg" id="checkImg" style="position:relative; top:6px; left:2px; " onClick="javascript:changePic()"/>
		      </td>
            </tr>

 3、JS调用部分

//ExtJS获取Session的值
     function getSesssionName (){ 
		 var name = <%=(String)session.getAttribute("vcode_sRand")%>; 
	 } 
	
	 function changePic() {
			document.getElementById('checkImg').src='servlet/RandCode?temp='+ (new Date().getTime().toString(36)); 
			return false;
	 }

 5. 配置文件部分

  <servlet-mapping>
    <servlet-name>RandCode</servlet-name>
    <url-pattern>/servlet/RandCode</url-pattern>
  </servlet-mapping>
  <servlet-mapping>
    <servlet-name>CheckCodeServlet</servlet-name>
    <url-pattern>/servlet/CheckCodeServlet</url-pattern>
  </servlet-mapping>