JavaWeb 网页的账号密码登录及验证码判断

1.首先在main文件夹中创建一个java文件夹标记为源码根，在java文件夹内创建包，在刚刚创建的包中创建CaptcheController的java类和loginController的Java类，以及StrUtil的Java类。如图所示：

loginController ：

package cn.edu.mju.project13.controller;

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.io.IOException;
import java.io.PrintWriter;

@WebServlet("/login")
public class logincontroller extends HttpServlet{
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {

        StringBuilder stringBuilder= new StringBuilder();
        stringBuilder.append("<form action='' method='post'>");
        stringBuilder.append("账号：<input type='text' name='loginName' value=''><br>");
        stringBuilder.append("密码：<input type='password' name='loginPwd' value=''><br>");
        stringBuilder.append("验证码：<input type='text' name='validCode' value=''><img src='./captche' width='100',height='80'><br>");
        stringBuilder.append("<input type='submit' name='submit' value='登录'>");
        stringBuilder.append("<input type='reset' name='reset' value='取消'>");
        stringBuilder.ap