Spring MVC：请求的资源不可用

Question

I am new to Spring framework exploring sample project where my jsp page will have a table to list out customer details which is already present in DB and there is Add Customer and Update & delete existing customer button. 

When I click Add Customer or Update Delete button 404 error is shown. 
Went through various answers in StackOverflow but issue not resolved yet. If someone can help here.

**Web.xml:**

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>CustomerManagementSystem</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>main-page.jsp</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.jsp</welcome-file>
    <welcome-file>default.htm</welcome-file>
    
  </welcome-file-list>
  <absolute-ordering/>
  <servlet>
    <servlet-name>dispatcher</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <init-param>
      <param-name>contextConfigLocation</param-name>
      <param-value>/WEB-INF/spring-mvc-demo-servlet.xml</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
    <servlet-name>dispatcher</servlet-name>
    <url-pattern>/</url-pattern>
  </servlet-mapping>
</web-app>

**servlet.xml:**

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:mvc="http://www.springframework.org/schema/mvc"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd
        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc.xsd">

    <!-- Add support for component scanning -->
    <context:component-scan
        base-package="com.gl.lib.cust"/>



    <!-- Define Spring MVC view resolver -->
    <bean
        class="org.springframework.web.servlet.view.InternalResourceViewResolver"
        id="jspViewResolver">
        <property name="viewClass"
            value="org.springframework.web.servlet.view.JstlView"></property>
        <property name="prefix" value="/WEB-INF/views/"></property>
        <property name="suffix" value=".jsp"></property>
    </bean>

    <bean
        class="org.springframework.jdbc.datasource.DriverManagerDataSource"
        id="dataSource">
        <property name="driverClassName"
            value="com.mysql.jdbc.Driver"></property>
        <property name="url"
            value="jdbc:mysql://localhost:3306/CustomerRelationshipManagement"></property>
        <property name="username" value="root"></property>
        <property name="password" value="password"></property>
    </bean>

    <bean id="sessionFactory"
        class="org.springframework.orm.hibernate5.LocalSessionFactoryBean">
        <property name="dataSource" ref="dataSource"></property>
        <property name="annotatedClasses">
            <list>
                <value>com.gl.lib.cust.Customer</value>
            </list>
        </property>
        <property name="hibernateProperties">
            <props>
                <prop key="hibernate.dialect">org.hibernate.dialect.MySQL8Dialect</prop>
                <prop key="hibernate.show_sql">true</prop>
                <prop key="hibernate.hbm2ddl.auto">update</prop>
            </props>
        </property>
    </bean>

    <bean id="myTransactionManager"
        class="org.springframework.orm.hibernate5.HibernateTransactionManager">
        <property name="sessionFactory" ref="sessionFactory" />
    </bean>


</beans>


**Three JSP pages**

**main-page.jsp**

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<!-- Required meta tags -->
<meta charset="utf-8">
<meta name="viewport"
    content="width=device-width, initial-scale=1, shrink-to-fit=no">

<!-- Bootstrap CSS -->
<link rel="stylesheet"
    href="https://stackpath.bootstrapcdn.com/bootstrap/4.2.1/css/bootstrap.min.css"
    integrity="sha384-GJzZqFGwb1QTTN6wy59ffF1BuGJpLSa9DkKMp0DgiMDm4iYMj70gZWKYbI706tWS"
    crossorigin="anonymous">

<title>Customer Directory</title>
</head>

<body>

    <div class="container">

        <h3 style="background-color:green;">CUSTOMER RELATIONSHIP MANAGEMENT</h3>
        <hr>
<form action="/CustomerManagementSystem/customer/showFormForAdd"
            class="form-inline">
            <a href="/CustomerManagementSystem/customer/showFormForAdd">
                <button class="btn btn-primary btn-sm mb-3">Add Customer</button>
            </a>
        
        </form> 

        <table class="table table-bordered table-striped">
            <thead>
                <tr>
                    <th>First Name</th>
                    <th>Last Name</th>
                    <th>Email</th>
                    <th>Action</th>
                </tr>
            </thead>

            <tbody>
                <c:forEach items="${customer}" var="temp">
                    <tr>
                        <td><c:out value="${temp.fname}" /></td>
                        <td><c:out value="${temp.lname}" /></td>
                        <td><c:out value="${temp.email}" /></td>
                        <td>
                            <!-- Add "update" button/link --> <a
                            href="/CustomerManagementSystem/customer/showFormForUpdate?email=${temp.email}"> Update </a> 
                            <a
                            href="/CustomerManagementSystem/customer/delete?email=${temp.email}"
                            onclick="if (!(confirm('Are you sure you want to delete this student?'))) return false">
                                Delete </a>

                        </td>

                    </tr>
                </c:forEach>

            </tbody>
        </table>

    </div>

</body>
</html>



**Customer-form.jsp**

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<!-- Required meta tags -->
<meta charset="utf-8">
<meta name="viewport"
    content="width=device-width, initial-scale=1, shrink-to-fit=no">

<!-- Bootstrap CSS -->
<link rel="stylesheet"
    href="https://stackpath.bootstrapcdn.com/bootstrap/4.2.1/css/bootstrap.min.css"
    integrity="sha384-GJzZqFGwb1QTTN6wy59ffF1BuGJpLSa9DkKMp0DgiMDm4iYMj70gZWKYbI706tWS"
    crossorigin="anonymous">

<title>Save Customer</title>
</head>

<body>

    <div class="container">

        <h3>CUSTOMER RELATIONSHIP MANAGEMENT</h3>
        <hr>

        <p class="h4 mb-4">Save Customer</p>

        <form action="/CustomerManagementSystem/customer/save" method="POST">


            <div class="form-inline">
                <input type="text" name="name" value="${customer.fname}"
                    class="form-control mb-4 col-4" placeholder="First Name:">



            </div>

            <div class="form-inline">

                <input type="text" name="category" value="${customer.lname}"
                    class="form-control mb-4 col-4" placeholder="Last Name:">



            </div>

            <div class="form-inline">

                <input type="text" name="author" value="${customer.email}"
                    class="form-control mb-4 col-4" placeholder="Email:">



            </div>
            

            <button type="submit" class="btn btn-info col-2">Save</button> 

        </form>

        <hr>
     <a href="/CustomerManagementSystem/customer/list">Back to List</a> 

    </div>
</body>

</html>


**Update-form.jsp:**

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>

    <div class="container">

        <h3>CUSTOMER RELATIONSHIP MANAGEMENT</h3>
        <hr>

        <p class="h4 mb-4">Save Customer</p>

        <form action="/CustomerManagementSystem/customer/update" method="POST">

            
            

            <button type="submit" class="btn btn-info col-2">Save</button> 

        </form>
<table class="table table-bordered table-striped">
            <!-- <thead class="thead-dark">
                <tr>
                    <th>First Name</th>
                    <th>Last Name</th>
                    <th>Email</th>
                    <th>Action</th>
                </tr>
            </thead> -->

            <tbody>
                <c:forEach items="${customer}" var="temp">
                    <tr>
                        <td>First Name: <c:out value="${temp.fname}" /></td>
                        <td>Last Name: <c:out value="${temp.lname}" /></td>
                        <td>Email: <c:out value="${temp.email}" /></td>
                        <td>
                            <!-- Add "save" button/link --> <a
                            href="/CustomerManagementSystem/customer/showFormForUpdate?email=${temp.email}"
                            class="btn btn-info btn-sm"> Save </a> 

                        </td>

                    </tr>
                </c:forEach>

            </tbody>
        </table>
        <hr>
     <a href="/StudentManagementSystem/student/list">Back to List</a> 

    </div>
</body>

</html>



**Controller Class**

package com.gl.lib.cust;

import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;


@Controller
@RequestMapping("/customer")
public class CustomerController {

    @Autowired
    private CustomerServiceImplementation customerService;


    @RequestMapping("/print")
    public String listCustomer(Model theModel) {
        List<Customer> ct = customerService.findAll();

        // add to the spring model
        theModel.addAttribute("customer", ct);

        return "main-page";
    }

    @RequestMapping("/showFormForAdd")
    public String showFormForAdd(Model theModel) {

        Customer ct = new Customer();
        theModel.addAttribute("customer", ct);

        return "Customer-form";
    }

    @RequestMapping("/showFormForUpdate")
    public String showFormForUpdate(@RequestParam("email") String email,
            Model theModel) {

        Customer ct = customerService.findByEmail(email);

        theModel.addAttribute("customer", ct);

        return "Update-form";           
    }


    @PostMapping("/save")
    public String saveCustomerRecord(@RequestParam("fname") String fname,
            @RequestParam("lname") String lname,@RequestParam("email") String email) {

        Customer ct;
        ct=new Customer(fname, lname, email);
        customerService.save(ct);
        // use a redirect to prevent duplicate submissions
        return "redirect:/customer/list";

    }


    @RequestMapping("/delete")
    public String delete(@RequestParam("email")String email) {

        //  customerService.delete(email);

        // redirect to /Books/list
        return "redirect:/student/list";

    }

    public String index() {
        return "forward:/customer/main-page.jsp";
    }   

}

我的 main-page.jsp 已正确加载，并且显示了所有主页数据，但导航到其他 2 个页面失败。

尽管 url 的格式正确。例如，当我选择“添加客户”按钮时，形成的 URL 为“http://localhost:8080/CustomerManagementSystem/customer/showFormForAdd?”

我在控制器类中映射了 showFormForAdd，并将其路由到 Customer-form.jsp 页面。我在这里错过了什么吗？

Eclipse 项目结构：

Answer 1

您的主菜单正在加载，因为您在 web.xml 中将其定义为欢迎文件。

您确定视图文件夹中有 Customer-form 和 Update-form JSP 文件吗？或者您是否以不同的方式命名它们，因为控制器返回的字符串值必须与 JSP 页面名称匹配？

另外，根据您的 Eclipse 版本，当您创建新的动态 Web 项目时，Eclipse 将创建 webapp 文件夹或 WebContent 文件夹，这就是您需要遵循的项目结构。

如果您的 Eclipse 创建了 webapp 文件夹，您无法真正创建 WebContent 文件夹并期望它能够工作。
以下是 WebContent 文件夹和 webapp 文件夹的动态 Web 项目的正确结构

这也是您的 ViewResolver bean 的样子

<bean class = "org.springframework.web.servlet.view.InternalResourceViewResolver">
   <property name = "prefix" value = "/WEB-INF/views/"/>
   <property name = "suffix" value = ".jsp"/>
</bean>