jsp验证码实现代码

1.后台java代码

package com.bobo.base.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;

/**
* <p>Title:用于产生校验码的servlet类</p>
* <p>Description: 用于产生校验码的servlet类</p>
* @author
* @version 1.0 2010-09-05
*/

@SuppressWarnings("serial")
public class CheckCodeServlet extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

//设置页面不缓存
response.setHeader("Pragma", "No-cache");
response.setHeader("Cache-Control", "no-cache");
response.setDateHeader("Expires", 0);

// 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
// 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.setColor(new Color(20 + random.nextInt(110), 20 + random.nextInt(110), 20 + random.nextInt(110)));
g.drawString(rand, 13 * i + 6, 16);
}

// 将认证码存入SESSION
request.getSession().setAttribute("checkCode", sRand);

// 图象生效
g.dispose();

// 输出图象到页面
ImageIO.write(image, "JPEG", response.getOutputStream());
}
/**
* 获取随机颜色
* @param fc
* @param bc
* @return
*/
private Color getRandColor(int fc,int bc) {
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.web.xml配置
<servlet>
<servlet-name>checkCodeServlet</servlet-name>
<servlet-class>com.bobo.base.servlet.CheckCodeServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>checkCodeServlet</servlet-name>
<url-pattern>/checkCode.jpg</url-pattern>
</servlet-mapping>

3.jsp页面调用
<tr>
<th>验证码:</th>
<td><input id="checkCode" name="checkCode" size="30" maxlength="6" type="text" value="" style="ime-mode:disabled"/><img src='checkCode.jpg' class="code" /></td>
</tr>

4.java验证代码：
session中拿到checkCode的值与jsp页面传入的值checkCode进行比较。