Java Implementation Web page verification code

Servlet:

Package Cn.bdqn.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.font.imagegraphicattribute;import Java.awt.image.bufferedimage;import Java.io.IOException;import Java.util.Random; @WebServlet (name = "Servlet", Urlpatterns = "/yancode") public class Servlet extends HttpServlet {publi c void DoPost (Javax.servlet.http.HttpServletRequest request, httpservletresponse response) throws Servletexception,    IOException {this.doget (request,response);        } public void Doget (HttpServletRequest request, httpservletresponse response) throws Servletexception, IOException {        String s= "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";        Random random = new random ();        int width=500;        int height=50; BufferedImage image = NEW BufferedImage (WIDTH,HEIGHT,BUFFEREDIMAGE.TYPE_INT_RGB);        Graphics graphics = Image.getgraphics ();//equivalent brush//painting Background graphics.setcolor (Color.gray);        Graphics.fillrect (0,0,width,height);        Graphics.setcolor (Color.Black);            for (int i = 0; I <4; i++) {int index = Random.nextint (S.length ());            String C = s.substring (index, index + 1);        Graphics.DrawString (c,width/5* (i+1), 15);    } imageio.write (image, "JPG", Response.getoutputstream ()); }}

Jsp:

<%--  Created by IntelliJ idea.  User:administrator  DATE:2017/10/10 time:13:04 To change this  template use  File | Settings | File templates.--%><%@ page contenttype= "Text/html;charset=utf-8" language= "java"%>