版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/ScongHW/article/details/81256338
1.使用BufferedImage类来生成验证码图片
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.PrintWriter;
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;
/**
*生成验证码
*/
public class ImageServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
int width = 200;
int height = 35;
//创建一张图片
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_BGR);
//得到该图片
Graphics g = image.getGraphics();
//设置图片的背景色
g.setColor(Color.GRAY);
//设置图片边框
g.fillRect(1, 1, width-2, height-2);
//设置边框颜色
g.setColor(Color.blue);
g.drawRect(0, 0, width, height);
//设置干扰线颜色
g.setColor(Color.white);
//画干扰线
Random r = new Random();
for(int i=0;i<10;i++){
g.drawLine(r.nextInt(width), r.nextInt(height), r.nextInt(width), r.nextInt(height));
}
StringBuffer sb = new StringBuffer();
g.setColor(Color.RED);
Font f = new Font("宋体",Font.BOLD,30);
g.setFont(f);
int x=30;
//在图片上写数字(也可以写其他的)
for(int i=0;i<4;i++){
String code = String.valueOf(r.nextInt(10));
g.drawString(code, x, 25);
x+=30;
sb.append(code);
}
//将验证码存入session中，方便验证输入是否正确
HttpSession session = request.getSession();
session.setAttribute("scode", sb.toString());
//将图片写给浏览器
ImageIO.write(image, "jpg" , response.getOutputStream());
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
2.在表单中使用验证码图片
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>验证码</title>
</head>
<body>
<form action="${pageContext.request.contextPath }/servlet/LoginServlet" method="post">
用户名：<input name="name" type="text" /><br/>
验证码：<input name="fcode" type="text"/>
<img src="${pageContext.request.contextPath }/servlet/ImageServlet" width="200px" height="35px">
<br/>
<input type="submit" value="提交"/>
</form>
</body>
</html>效果图：
3.服务器对提交的数据进行验证
import java.io.IOException;
import java.io.PrintWriter;
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 LoginServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String name = request.getParameter("name");
String fcode = request.getParameter("fcode");
HttpSession session = request.getSession();
String scode = (String) session.getAttribute("scode");
if (scode != null) {
if (scode.equals(fcode)) {
session.removeAttribute("scode");//第一次登陆成功之后移除session
response.getWriter().write("success");
} else {//验证码输出错误
response.getWriter().write("false");
}
}else{//如果session不存在
response.getWriter().write("resubmit");
}
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}