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javaweb项目，有两个文件，一个java文件，用来生成验证码并输出到servlet输出流中。一个html文件，用来写组件和点击事件，刷新验证码。
CodeServlet.java文件
package net.test.servlet;
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;
@WebServlet(name = "CodeServlet",urlPatterns = "/code")
public class CodeServlet extends HttpServlet {
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
}
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
int width=100;
int height=30;
String str="qwertyuiopasdfghjklzxcbnm123456789";
Random random = new Random();
BufferedImage image=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
Graphics graphics = image.getGraphics();
graphics.drawRect(0,0,100,30);
for (int i = 0; i < 4; i++) {
int number=random.nextInt(str.length());
String a=str.substring(number,number+1);
graphics.drawString(a,20*(i+1),15);
}
ImageIO.write(image,"jpg",resp.getOutputStream());
}
}
login.html文件
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>验证码</title>
</head>
<body>
<image id="verifycode" src="code" onclick="this.src=this.src+'?'+Math.random()" "btn.isDisable=false"></image>
<button id="btn" onclick="document.getElementById('verifycode').click()">刷新验证码</button>
</body>
</html>
运行结果：
点击图片或者按钮，都能刷新验证码
