java Servlet产生验证码图片
1、书写验证码产生程序：
package com.bobo.shopping.common.util;
/**
* Title:用于产生校验码的servlet类
* Description:用于产生校验码的servlet类
* @version 1.0
*/
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;
public class CheckCodeServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
private static int codeLength = 4; //验证码位数
private static int imageWidth = 60; //图片宽度
private static int imageHeight = 20; //图片高度
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
BufferedImage image = new BufferedImage(imageWidth, imageHeight, 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, imageWidth, imageHeight);
//设定字体
g.setFont(new Font("Times New Roman", Font.PLAIN, 18));
//画边框
g.setColor(new Color(20,20,20));
g.drawRect(0, 0, imageWidth - 1, imageHeight - 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(imageWidth);
int y = random.nextInt(imageHeight);
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
// 可以自己设置数字字母等，本例只是产生数字
String sRand = "";
for (int i = 0;i < codeLength; 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中
// 获取方式 request.getSession().getAttribute("checkCode");
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
<!-- 验证码servlet start -->
<servlet>
<servlet-name>checkCodeServlet</servlet-name>
<servlet-class>
com.bobo.shopping.common.util.CheckCodeServlet
</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>checkCodeServlet</servlet-name>
<url-pattern>/checkCode.jpg</url-pattern>
</servlet-mapping>
<!-- 校验码servlet end -->
3、jsp页面调用方法：
<img src="<%=basePath%>checkCode.jpg"/>
4、提交后 后台获取本来产生验证码方法：
request.getSession().getAttribute("checkCode");
与提交的验证码进行比较即可。