JavaNote 3.5 Servlet简单的验证码

一、前端代码

<body>
    <script typeof="text/javascript">
        var c = 0;
        var id ;
        function changeCode() {
            document.getElementById("identity").src='code?ts=' + new Date().getTime();
            countTime();
        }
        function countTime() {
            id = setTimeout(countTime, 1000);
            c = c + 1;
            if (c < 50) {
                document.getElementById("butt").value = 60 - c;
                document.getElementById("butt").disabled = true;
            }
            else if(c > 50&& c < 60){
                document.getElementById("butt").value = "0" + (60 - c); 
                document.getElementById("butt").disabled = true;
            }
            else {
                document.getElementById("butt").value = "请点击";
                document.getElementById("butt").disabled = false;
                c = 0;
                clearTimeout(id);
            }
        }
    </script>
    <img src="code" alt="" id="identity"  style="cursor: pointer">
    <input type="button" id="butt" onclick="changeCode()" value="请点击" width="100" height="30"  >
</body>

二、Servlet代码

package com.zxw.helloServlet;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
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 = "VerifyCode",urlPatterns = "/code")
public class VerifyCode extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String data = "013456789";//定义数据池
        Random random = new Random();
        int width = 100;
        int heigth = 30;
        BufferedImage image = new BufferedImage(width,heigth,BufferedImage.TYPE_INT_RGB);
        Graphics graphics = image.getGraphics();
        graphics.setColor(Color.GRAY);//这个颜色的设置只会针对上文，所以下面还需要设置
        graphics.fillRect(0,0,width,heigth);
        graphics.setColor(Color.black);

        for(int i=0;i<4;i++){
            int possion = random.nextInt(data.length());
            String msg = data.substring(possion,possion + 1);
            graphics.drawString(msg,width/5*(i+1),15);
        }
        ImageIO.write(image,"jpg",response.getOutputStream());


    }
}

三、效果展示