如何解决 Servlet 应用程序中出现 405 错误并在 servlet 文件中发布数据？

Question

我是 java servlet 和 JSP 的新手。 我正在构建一个测验应用程序，它现在具有两个功能，即登录和 SingUp。 注册页面具有客户端和服务器端验证，这两个单独工作正常，即如果在表单中输入数据并单击提交按钮，则数据在服务器端验证并插入数据库，但当 jsp 文件与 javascript 连接，数据不会插入数据库。

• 我希望在客户端验证数据。
• 完全验证后，将数据发布到服务器端，即 servlet 文件进行验证（这是发生错误的地方）。
• 在完全验证@服务器端后，将数据插入数据库。 这是我面临的错误：

错误 405: Method Not Allowed 消息 HTTP 方法 GET 不受此 URL 支持 说明 请求行中接收的方法是源服务器已知的，但目标资源不支持。

到目前为止，这是我的代码： Servlet File

import java.io.IOException;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/Register")
public class Register extends HttpServlet {
    private static final long serialVersionUID = 1L;
    
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String fname = request.getParameter("firstname");
        String lname = request.getParameter("lastname");
        String email = request.getParameter("email");
        String password = request.getParameter("password");
        
        Member member = new Member(fname, lname, email, password);
        RegisterDao rDao = new RegisterDao();
        String result = rDao.insert(member);
        RequestDispatcher dispatcher = request.getRequestDispatcher("memberRegistration.jsp");
        
        if (result.equals("data not entered")) {
            request.setAttribute("hiddenalert", "failed");
            //response.sendRedirect("login.jsp");
        } else {
            request.setAttribute("hiddenalert", "success");
            //response.sendRedirect("dashboard-student.jsp");
        }
        dispatcher.forward(request, response);
    }
}

Database Connectivity Class

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;

public class RegisterDao {
    private String dbUrl = "jdbc:mysql://localhost:3306/dbname?useSSL=false";
    private String dbusername = "username";
    private String dbpassword = "password";
    private String dbDriver = "com.mysql.cj.jdbc.Driver";
    
    public void loadDriver(String dbDriver) {
        try {
            Class.forName(dbDriver);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
    
    public Connection getConnection() {
        Connection con = null;
        try {
            con = DriverManager.getConnection(dbUrl, dbusername, dbpassword);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return con;
    }
    
    public String insert (Member member) {
        loadDriver(dbDriver);
        Connection con = getConnection();
        String result = "data entered successfully";
        String sql = "insert into quizzbuzz.users(fname, lname, email, passwords) values(?, ?, ?, ?)";
        
        PreparedStatement ps;
        try {
            ps = con.prepareStatement(sql);
            ps.setString(1, member.getFname());
            ps.setString(2, member.getLname());
            ps.setString(3, member.getEmail());
            ps.setString(4, member.getPassword());
            ps.executeUpdate();
            
        } catch (SQLException e) {
            e.printStackTrace();
            result = "data not entered";
        } finally {
            try {
                con.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        return result;
    }
}

javascript file

const form = document.getElementById('register-form');
const fname = document.getElementById('fname');
const lname = document.getElementById('lname');
const email = document.getElementById('email');
const password = document.getElementById('password');

// add event
form.addEventListener('submit', (event) => {
    event.preventDefault();
    validate();
})

const sendData = (fnameVal, sRate, count) => {
    if (sRate === count) {
        //location.href = `dashboard-student.jsp?fname=${fnameVal}`;
        location.href = `Register`;
    }
}

const successMsg = (fnameVal) => {
    let formG = document.getElementsByClassName('form-group');
    var count = formG.length - 1;
    for (var i = 0; i < formG.length; i++) {
        if (formG[i].className === "form-group success") {
            var sRate = 0 + i;
            sendData(fnameVal, sRate, count);
        } else {
            return false;
        }
    }
}

const isEmail = (emailVal) => {
    var atSymbol = emailVal.indexOf("@");
    if (atSymbol < 1) return false;
    var dot = emailVal.indexOf('.');
    if (dot === emailVal.length - 1) return false;
    return true;
}

const validate = () => {
    const fnameVal = fname.value.trim();
    const lnameVal = lname.value.trim();
    const emailVal = email.value.trim();
    const passwordVal = password.value.trim();
        
    // validate first-name
    if (fnameVal === "") {
        setErrorMsg(fname, 'first-name cannot be blank');
    } else if (fnameVal.length <= 2) {
        setErrorMsg(fname, 'first-name requires min 3 char');
    } else {
        setSuccessMsg(fname);
    }

    // check last-name
    if (lnameVal === "") {
        setErrorMsg(lname, 'last-name cannot be blank');
    } else if (lnameVal.length <= 2) {
        setErrorMsg(lname, 'last-name requires min 3 char');
    } else {
        setSuccessMsg(lname);
    }

    // check email
    if (emailVal === "") {
        setErrorMsg(email, 'email cannot be blank');
    } else if (!isEmail(emailVal)) {
        setErrorMsg(email, 'not valide email');
    } else {
        setSuccessMsg(email);
    }

    if (passwordVal === "") {
        setErrorMsg(password, 'password cannot be blank');
    } else if (passwordVal.length <= 5) {
        setErrorMsg(password, "Minimum 6 char required")
    } else {
        setSuccessMsg(password);
    }
    successMsg(fnameVal);
}

function setErrorMsg(input, errormsgs) {
    const formGroup = input.parentElement;
    const small = formGroup.querySelector('small');
    formGroup.className = "form-group error";
    small.innerText = errormsgs;
}

function setSuccessMsg(input) {
    const formGroup = input.parentElement;
    formGroup.className = "form-group success";
}

var status = document.getElementById("status").value;
if (status == "success") {
    swal("Congratulations", "Account Created Successfully", "success");
} 

JSP file

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>QuizzBuzz Sign-Up Portal</title>

    <link rel="stylesheet" href="./css/registration-style.css">

    <!--font-->
    <link rel="preconnect" href="https://fonts.googleapis.com">
    <link rel="preconnect" href="https://fonts.gstatic.com">
    <link href="https://fonts.googleapis.com/css2?family=Poppins&display=swap" rel="stylesheet">
</head>
<body>
<input type="hidden" name="hiddenalert" id = "status" value = "<%= request.getAttribute("hiddenalert") %>">
    <div class="main">
        <section class="signup">
            <div class="container">
                <div class="signup-content">
                    <div class="signup-image">
                        <figure>
                            <img src="./images/signup-image.jpg" alt="singup-image">
                        </figure>
                    </div>
                    <div class="signup-form">
                        <h2 class="title">Create an Account</h2>
                        <form method="post" action="Register" class="register-form" id="register-form" novalidate>
                            <div class="form-group">
                                <input type="text" name="firstname" id="fname" placeholder="Enter your first-name" autocomplete="off" required="required">
                                <i class="fa-solid fa-circle-check"></i>
                                <i class="fa-solid fa-exclamation-circle"></i>
                                <small>Error!</small>
                            </div>
                            <div class="form-group">
                                <input type="text" name="lastname" id="lname" placeholder="Enter your last-name" autocomplete="off" required="required">
                                <i class="fa-solid fa-circle-check"></i>
                                <i class="fa-solid fa-exclamation-circle"></i>
                                <small>Error!</small>
                            </div>
                            <div class="form-group">
                                <input type="email" name="email" id="email" placeholder="Enter your Email ID" autocomplete="off" required="required">
                                <i class="fa-solid fa-circle-check"></i>
                                <i class="fa-solid fa-exclamation-circle"></i>
                                <small>Error!</small>
                            </div>
                            <div class="form-group">
                                <input type="password" name="password" id="password" placeholder="Enter your password" autocomplete="off" required="required">
                                <i class="fa-solid fa-circle-check"></i>
                                <i class="fa-solid fa-exclamation-circle"></i>
                                <small>Error!</small>
                            </div>
                            <input type="submit" value="Submit" class="button">
                        </form>
                    </div>
                </div>
            </div>
        </section>
    </div>
    <script src="https://unpkg.com/sweetalert/dist/sweetalert.min.js"></script>
    <script src="./js/member-registration.js"></script>
</body>
</html>