使用Servlet生成验证码
本文演示如何在Servlet中生成随机验证码。
1 编写index.jsp
index.jsp:
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>一点教程网-使用Servlet生成验证码</title>
</head>
<body>
<h1>使用Servlet生成验证码</h1>
<a href="VaidateCode">生成验证码</a>
</body>
</html>
2 编写ImageUtil
ImageUtil用于生成随机验证码：
import javax.servlet.http.HttpSession;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.util.Random;
/**
* 一点教程网 - http://www.yiidian.com
*/
public class ImageUtil {
private ImageUtil() {};
private static final Random r = new Random();
private static final int width = 148;
private static final int height = 26;
private static final char[] c= {
'a','b','c','d','e','f','g','h','i','j',
'k','l','m','n','o','p','q','r','s','t',
'u','v','w','x','y','z',
'0','1','2','3','4','5','6','7','8','9'
};
public static final BufferedImage createImage(HttpSession session, int length) {
//根据宽高创建一张缓冲区图像, 图像使用的是正整数的RGB格式
BufferedImage bi = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
//从图像中获取画笔
Graphics g = bi.getGraphics();
//设置画笔颜色
g.setColor(new Color(175,215,151));
//使用画笔填充矩形,背景色
setBackGround(g);
//设置干扰线
drowRandomLine((Graphics2D)g);
StringBuilder sb = new StringBuilder();
for(int i=0; i < length; i++) {
int index = r.nextInt(c.length);
sb.append(c[index]);
//设置字体
g.setFont(new Font("微软雅黑",Font.PLAIN,r.nextInt(5)+15));
g.setColor(new Color(r.nextInt(200),r.nextInt(200),r.nextInt(200)));
g.drawString(Character.toString(c[index]), (i+1)*20, 18);
}
//将验证码存入到session中
session.setAttribute("sb", sb.toString());
g.dispose();
return bi;
}
/** 设置背景颜色 */
private static void setBackGround(Graphics g) {
//设置画笔颜色
g.setColor(Color.white);
//填充区域
g.fillRect(0, 0, width, height);
}
/** 干扰线 */
private static void drowRandomLine(Graphics2D g) {
g.setStroke(new BasicStroke(0.3f));
//设置线条数目, 线条颜色
for(int i=0; i<3;i++) {
//每次颜色随机
g.setColor(new Color(r.nextInt(10),r.nextInt(10),r.nextInt(10)));
int x1 = r.nextInt(width);
int y1 = r.nextInt(height);
int x2 = r.nextInt(width);
int y2 = r.nextInt(height);
g.drawLine(x1, y1, x2, y2);
}
}
}
3 编写VaidateCodeServlet
ValidateCodeServlet用于调用ImageUtil展示随机验证码到浏览器：
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.image.BufferedImage;
import java.io.*;
/**
* 一点教程网 - http://www.yiidian.com
*/
public class VaidateCodeServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//创建图像
BufferedImage bi = ImageUtil.createImage(request.getSession(), 5);
//以png格式 输出响应流到界面
ImageIO.write(bi, "png", response.getOutputStream());
/** 设置浏览器不缓存图片*/
response.setHeader("Cache-Control", "no-cache");
response.setHeader("Pragma", "no-cache");
response.setDateHeader("expires", -1);
}
}
4 配置web.xml
web.xml:
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
version="3.1">
<servlet>
<servlet-name>VaidateCodeServlet</servlet-name>
<servlet-class>VaidateCodeServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>VaidateCodeServlet</servlet-name>
<url-pattern>/VaidateCode</url-pattern>
</servlet-mapping>
</web-app>
5 运行测试
热门文章
优秀文章
