SpringMVC 13. RESTful CRUD

不念不忘少年蓝@ 2022-05-24 22:53 204阅读 0赞

# RESTful CRUD #

## 1 前置准备 ##

### 1.0 配置文件 ###

*  pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
      <modelVersion>4.0.0</modelVersion>
      <groupId>com.ifox.hgx</groupId>
      <artifactId>springMVC_1</artifactId>
      <packaging>war</packaging>
      <version>1.0-SNAPSHOT</version>
      <name>springMVC_1 Maven Webapp</name>
      <url>http://maven.apache.org</url>
    
      <dependencies>
    
        
        <dependency>
          <groupId>org.springframework</groupId>
          <artifactId>spring-webmvc</artifactId>
          <version>5.0.3.RELEASE</version>
        </dependency>
    
        
        <dependency>
          <groupId>javax.servlet</groupId>
          <artifactId>javax.servlet-api</artifactId>
          <version>3.1.0</version>
          <scope>provided</scope>
        </dependency>
    
      </dependencies>
      <build>
        <finalName>springMVC_1</finalName>
      </build>
    </project>

*  web.xml

<?xml version="1.0" encoding="UTF-8"?>
    <web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" version="3.1">
    
    
    
    
        
        <filter>
            <filter-name>CharacterEncodingFilter</filter-name>
            <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
            <init-param>
                <param-name>encoding</param-name>
                <param-value>utf-8</param-value>
            </init-param>
        </filter>
    
        <filter-mapping>
            <filter-name>CharacterEncodingFilter</filter-name>
            <url-pattern>/*</url-pattern>
        </filter-mapping>
    
        
        <filter>
            <filter-name>HiddenHttpMethodFilter</filter-name>
            <filter-class>org.springframework.web.filter.HiddenHttpMethodFilter</filter-class>
        </filter>
        <filter-mapping>
            <filter-name>HiddenHttpMethodFilter</filter-name>
            <url-pattern>/*</url-pattern>
        </filter-mapping>
    
        <servlet>
            <servlet-name>springDispatcherServlet</servlet-name>
            <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
            
            
            <init-param>
                <param-name>contextConfigLocation</param-name>
                <param-value>classpath:springmvc.xml</param-value>
            </init-param>
            <load-on-startup>1</load-on-startup>
        </servlet>
        <servlet-mapping>
            <servlet-name>springDispatcherServlet</servlet-name>
            <url-pattern>/</url-pattern>
        </servlet-mapping>
    
    
    </web-app>

*  springmvc.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">
    
        
        <context:component-scan base-package="com.ifox"></context:component-scan>
    
        
        <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
            <property name="prefix" value="/WEB-INF/views/"></property>
            <property name="suffix" value=".jsp"></property>
        </bean>
    
        <mvc:annotation-driven></mvc:annotation-driven>
    
    </beans>

### 1.1 DAO ###

*  DepartmentDao.java

import com.ifox.restful_CRUD.entities.Department;
    import org.springframework.stereotype.Repository;
    
    import java.util.Collection;
    import java.util.HashMap;
    import java.util.Map;
    
    @Repository
    public class DepartmentDao { 
    
        private static Map<Integer, Department> departments = null;
    
        static {
            departments = new HashMap<Integer, Department>();
    
            departments.put(101, new Department(101, "D-AA"));
            departments.put(102, new Department(102, "D-BB"));
            departments.put(103, new Department(103, "D-CC"));
            departments.put(104, new Department(104, "D-DD"));
            departments.put(105, new Department(105, "D-EE"));
        }
    
        public Collection<Department> getDepartments() {
            return departments.values();
        }
    
        public Department getDepartment(Integer id) {
            return departments.get(id);
        }
    
    }

*  EmployeeDao.java

import java.util.Collection;
    import java.util.HashMap;
    import java.util.Map;
    
    import com.ifox.restful_CRUD.entities.Department;
    import com.ifox.restful_CRUD.entities.Employee;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Repository;
    
    
    @Repository
    public class EmployeeDao { 
    
        private static Map<Integer, Employee> employees = null;
    
        @Autowired
        private DepartmentDao departmentDao;
    
        //为了简化，省略了数据库，使用静态代码块代替
        static{
            employees = new HashMap<Integer, Employee>();
    
            employees.put(1001, new Employee(1001, "E-AA", "aa@163.com", 1, new Department(101, "D-AA")));
            employees.put(1002, new Employee(1002, "E-BB", "bb@163.com", 1, new Department(102, "D-BB")));
            employees.put(1003, new Employee(1003, "E-CC", "cc@163.com", 0, new Department(103, "D-CC")));
            employees.put(1004, new Employee(1004, "E-DD", "dd@163.com", 0, new Department(104, "D-DD")));
            employees.put(1005, new Employee(1005, "E-EE", "ee@163.com", 1, new Department(105, "D-EE")));
        }
    
        private static Integer initId = 1006;
    
        public void save(Employee employee){
            if(employee.getId() == null){
                employee.setId(initId++);
            }
    
            employee.setDepartment(departmentDao.getDepartment(employee.getDepartment().getId()));
            employees.put(employee.getId(), employee);
        }
    
        public Collection<Employee> getAll(){
            return employees.values();
        }
    
        public Employee get(Integer id){
            return employees.get(id);
        }
    
        public void delete(Integer id){
            employees.remove(id);
        }
    }

### 1.2 entities ###

*  Department.java

public class Department {
        private Integer id ;
        private String departmentName ;
    
        public Integer getId() {
            return id;
        }
    
        public void setId(Integer id) {
            this.id = id;
        }
    
        public String getDepartmentName() {
            return departmentName;
        }
    
        public void setDepartmentName(String departmentName) {
            this.departmentName = departmentName;
        }
    
        public Department(Integer id, String departmentName) {
            this.id = id;
            this.departmentName = departmentName;
        }
    
        public Department() {
        }
    
        @Override
        public String toString() {
            return "Department{" +
                    "id=" + id +
                    ", departmentName='" + departmentName + '\'' +
                    '}';
        }
    }

*  Employee.java

public class Employee {
        private Integer id ;
        private String lastName ;
        private String email ;
        private Integer gender ;
        private Department department ;
        private Date birth ;
    
        public Date getBirth() {
            return birth;
        }
    
        public void setBirth(Date birth) {
            this.birth = birth;
        }
    
        public Integer getId() {
            return id;
        }
    
        public void setId(Integer id) {
            this.id = id;
        }
    
        public String getLastName() {
            return lastName;
        }
    
        public void setLastName(String lastName) {
            this.lastName = lastName;
        }
    
        public String getEmail() {
            return email;
        }
    
        public void setEmail(String email) {
            this.email = email;
        }
    
        public Integer getGender() {
            return gender;
        }
    
        public void setGender(Integer gender) {
            this.gender = gender;
        }
    
        public Department getDepartment() {
            return department;
        }
    
        public void setDepartment(Department department) {
            this.department = department;
        }
    
        public Employee() {
        }
    
        public Employee(Integer id, String lastName, String email, Integer gender, Department department) {
            this.id = id;
            this.lastName = lastName;
            this.email = email;
            this.gender = gender;
            this.department = department;
        }
    
        public Employee(Integer id, String lastName, String email, Integer gender, Department department, Date birth) {
            this.id = id;
            this.lastName = lastName;
            this.email = email;
            this.gender = gender;
            this.department = department;
            this.birth = birth;
        }
    
         @Override
        public String toString() {
            return "Employee{" +
                    "id=" + id +
                    ", lastName='" + lastName + '\'' +
                    ", email='" + email + '\'' +
                    ", gender=" + gender +
                    ", department=" + department +
                    ", birth=" + birth +
                    '}';
        }
    }

## 2 显示所有员工信息（R） ##

*  URI：emps
 *  请求方式：GET
 *  显示效果

![所有员工信息][Image 1]

### 1.1 handlers ###

@Controller
    public class EmployeeHandler { 
        @Autowired
        private EmployeeDao employeeDao;
    
        @Autowired
        private DepartmentDao departmentDao ;
    
        @RequestMapping("/emps")
        public String list(Map<String, Object> map) {
            map.put("employees", employeeDao.getAll());
            return "list";
        }
    }

### 1.2 index.jsp ###

### 1.3 list.jsp 显示页面 ###

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
    <html>
    <head>
        <title>restful crud list</title>
    </head>
    <body>
    
    </form>
    
    <c:if test="${employees == null || employees.size()==0}">
        <p style="color: red;">没有任何内容</p>
    </c:if>
    
    <c:if test="${employees != null && employees.size() != 0}">
        <table border="1" cellspacing="0" cellpadding="10">
            <tr>
                <td>ID</td>
                <td>LastName</td>
                <td>Email</td>
                <td>Gender</td>
                <td>Department</td>
                <td>Edit</td>
                <td>Delete</td>
            </tr>
            <c:forEach items="${requestScope.employees }" var="emp">
                <tr>
                    <td>${emp.id }</td>
                    <td>${emp.lastName }</td>
                    <td>${emp.email }</td>
                    <td>${emp.gender == 0 ? 'Female' : 'Male' }</td>
                    <td>${emp.department.departmentName }</td>
                    <td><a href="emp/${emp.id}">Edit</a></td>
                    <td><a class="delete" href="emp/${emp.id}">Delete</a></td>
                </tr>
            </c:forEach>
        </table>
    </c:if>
    <br><br>
    
    <a href="emp">Add New Employee</a>
    
    </body>
    </html>

*  pom.xml 加入:

<dependency>
          <groupId>javax.servlet</groupId>
          <artifactId>jstl</artifactId>
          <version>1.2</version>
        </dependency>

此页面用到了SpringMVC的表单标签:

*  通过 SpringMVC 的表单标签可以实现将模型数据中的属性和 HTML 表单元素相绑定，以实现表单数据更便捷编辑和表单值的回显

### 1.4 form 标签 ###

*  一般情况下，通过 GET 请求获取表单页面，而通过POST 请求提交表单页面，因此获取表单页面和提交表单页面的 URL 是相同的。只要满足该最佳条件的契约，`<form:form>` 标签就无需通过 action 属性指定表单提交的 URL
 *  可以通过 modelAttribute 属性指定绑定的模型属性，若没有指定该属性，则默认从 request 域对象中读取command 的表单 bean，如果该属性值也不存在，则会发生错误。
 *  SpringMVC 提供了多个表单组件标签，如`<form:input/>`、`<form:select/>` 等，用以绑定表单字段的属性值，它们的共有属性如下：  
    `path`：表单字段，对应 html 元素的 name 属性，支持级联属性  
    `htmlEscape`：是否对表单值的 HTML 特殊字符进行转换，默认值为 true  
    `cssClass`：表单组件对应的 CSS 样式类名  
    `cssErrorClass`：表单组件的数据存在错误时，采取的 CSS 样式

`form:input、form:password、form:hidden、form:textarea`：对应 HTML 表单的 text、password、hidden、textarea标签

`form:radiobutton`：单选框组件标签，当表单 bean 对应的属性值和 value 值相等时，单选框被选中  
`form:radiobuttons`：单选框组标签，用于构造多个单选框

items：可以是一个 List、String[] 或 Map
         itemValue：指定 radio 的 value 值。可以是集合中 bean 的一个属性值
         itemLabel：指定 radio 的 label 值
         delimiter：多个单选框可以通过 delimiter 指定分隔符表单标签

`form:checkbox`：复选框组件。用于构造单个复选框  
`form:checkboxs`：用于构造多个复选框。使用方式同form:radiobuttons 标签  
`form:select`：用于构造下拉框组件。使用方式同form:radiobuttons 标签  
`form:option`：下拉框选项组件标签。使用方式同form:radiobuttons 标签  
`form:errors`：显示表单组件或数据校验所对应的错误 – `<form:errors path= “ *” />` ：显示表单所有的错误  
`<form:errors path= “ user*” />` ：显示所有以 user 为前缀的属性对应的错误  
`<form:errors path= “ username” />` ：显示特定表单对象属性的错误

## 3 添加新的员工（C） ##

### 3.1 Edit:显示添加员工页面 ###

显示添加页面：

*  URI：emp
 *  请求方式：GET

**示例:**

*  jsp页面:

<a href="emp">Add New Employee</a>

*  handlers：EmployeeHandler.java中加入

@RequestMapping(value = "/emp", method = RequestMethod.GET)
        public String input(Map<String, Object> map) {
            map.put("departments",departmentDao.getDepartments() ) ;
            map.put("employee",new Employee()) ;
            return "input" ;
        }

*  input.jsp

<%@ page import="java.util.Map" %>
    <%@ page import="java.util.HashMap" %>
    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <%@ taglib prefix="form" uri="http://www.springframework.org/tags/form" %>
    
    <html>
    <head>
        <title>restful CRUD input</title>
    </head>
    <body>
    <form:form action="${pageContext.request.contextPath}/emp" method="post" modelAttribute="employee">
    
        LastName: <form:input path="lastName"></form:input>
        <br>
        Email:<form:input path="email"></form:input>
        <br>
        <% Map<String,String> genders = new HashMap<>() ; genders.put("0","Male") ; genders.put("1","Female") ; request.setAttribute("genders",genders); %>
        Gender:<form:radiobuttons path="gender" items="${genders}" delimiter="  "></form:radiobuttons>
        <br>
        Department:<form:select path="department.id" items="${departments}" itemLabel="departmentName" itemValue="id" ></form:select>
        <br>
        Birth:<form:input path="birth"></form:input>
        <br>
        <input type="submit" value="Submit">
    </form:form>
    
    </body>
    </html>

点击后跳转到如下input.jsp页面

### 3.2 添加员工信息: ###

*  URI：emp
 *  请求方式：POST
 *  显示效果：完成添加，重定向到 list 页面。

![添加员工][70]

*  handlers:EmployeeHandler.java加入:

@RequestMapping(value = "/emp",method = RequestMethod.POST)
        public String save(Employee employee , Map<String,Object> map){
            System.out.println("save:"+employee);
            employeeDao.save(employee);
            return "redirect:/emps" ;
        }

点击提交，重定向到/emps 。

## 4 更新员工信息（U） ##

### 显示修改页面： ###

*  URI：emp/\{id\}
 *  请求方式：GET
 *  显示效果：回显表单。
 *  handlers:EmployeeHandler.java中添加:

@RequestMapping(value = "/emp/{id}",method = RequestMethod.GET)
        public String input(@PathVariable("id") Integer id ,Map<String,Object> map){
            map.put("employee",employeeDao.get(id)) ;
            map.put("departments",departmentDao.getDepartments()) ;
            return "input" ;
        }

list页面Edit:

点击跳转到修改页面，为了简化，修改和添加员工用一个页面，跳转到input.jsp，但是也有不同的地方，修改操作不允许修改员工名字，和 id 。

### 修改员工信息： ###

*  URI：emp
 *  请求方式：PUT
 *  显示效果：完成修改，重定向到 list 页面。  
    ![修改员工][70 1]
 *  注意我们在web.xml中加入的：

<filter>
            <filter-name>HiddenHttpMethodFilter</filter-name>
            <filter-class>org.springframework.web.filter.HiddenHttpMethodFilter</filter-class>
        </filter>
        <filter-mapping>
            <filter-name>HiddenHttpMethodFilter</filter-name>
            <url-pattern>/*</url-pattern>
        </filter-mapping>

*  handlers:EmployeeHandler.java中添加:

@ModelAttribute
        public void getEmployee(@RequestParam(value = "id",required = false) Integer id , Map<String,Object> map){
            if (id != null) {
                Employee e = employeeDao.get(id);
                map.put("employee",e) ;
            }
        }
    
        @RequestMapping(value = "/emp",method = RequestMethod.PUT )
        public String update(Employee employee){
           // employee.setLastName(employeeDao.get(employee.getId()).getLastName());
            employeeDao.save(employee);
            return "redirect:/emps" ;
        }

*  input.jsp页面:

<%@ page import="java.util.Map" %>
    <%@ page import="java.util.HashMap" %>
    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <%@ taglib prefix="form" uri="http://www.springframework.org/tags/form" %>
    <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
    
    <html>
    <head>
        <title>restful CRUD input</title>
    </head>
    <body>
    
    <form:form action="${pageContext.request.contextPath}/emp" method="post" modelAttribute="employee">
        <c:if test="${employee.id == null}">
        LastName: <form:input path="lastName"></form:input>
            <form:errors path="lastName" cssStyle="color: red"></form:errors>
        </c:if>
        <br>
    
        <c:if test="${employee.id != null}">
            <form:hidden path="id"></form:hidden>
            <input type="hidden" name="_method" value="PUT">
        </c:if>
        Email:<form:input path="email"></form:input>
        <br>
        <% Map<String,String> genders = new HashMap<>() ; genders.put("0","Male") ; genders.put("1","Female") ; request.setAttribute("genders",genders); %>
        Gender:<form:radiobuttons path="gender" items="${genders}" delimiter="  "></form:radiobuttons>
        <br>
        Department:<form:select path="department.id" items="${departments}" itemLabel="departmentName" itemValue="id" ></form:select>
        <br>
        Birth:<form:input path="birth"></form:input>
        <br>
        <input type="submit" value="Submit">
    </form:form>
    
    </body>
    </html>

*  在pom.xml中加入:

注意在其中我们写了一个@ModelAttribute注解修饰的方法，该方法会使得我们的employee是从数据库查到的，使得表单修改直接修改这个数据库查到的数据，从而避免了LastName在修改后为空的情况。

*  修改完成，submit后，重定向到/emps 。

## 5 删除员工（D） ##

### 删除操作 ###

*  URL：emp/\{id\}
 *  请求方式：DELETE
 *  删除后效果：对应记录从数据表中删除
 *  删除员工1001后:  
    ![删除员工1001][Image 1]
 *  list页面Delete:

<td><a class="delete" href="emp/${emp.id}">Delete</a></td>

注意：我们需要DELETE请求，但是只能由POST请求转为DELETE，这里是GET请求，所以我们使用js来实现，选用Jquery来做。

*  list.jsp修改为：

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
    <html>
    <head>
        <title>restful crud list</title>
        <%--处理静态资源--%>
        <%--添加--%>
        <script type="text/javascript" src="/scripts/jquery-1.9.1.min.js"></script>
        <script type="text/javascript"> $(function(){ $(".delete").click(function () { var href = $(this).attr("href") ; $("form").attr("action",href).submit() ; return false ; }) ; }) </script>
    </head>
    <body>
    
    <%--添加--%>
    <form name="form" method="post" action="">
        <input type="hidden" name="_method" value="DELETE">
    </form>
    
    <c:if test="${employees == null || employees.size()==0}">
        <p style="color: red;">没有任何内容</p>
    </c:if>
    
    <c:if test="${employees != null && employees.size() != 0}">
        <table border="1" cellspacing="0" cellpadding="10">
            <tr>
                <td>ID</td>
                <td>LastName</td>
                <td>Email</td>
                <td>Gender</td>
                <td>Department</td>
                <td>Edit</td>
                <td>Delete</td>
            </tr>
            <c:forEach items="${requestScope.employees }" var="emp">
                <tr>
                    <td>${emp.id }</td>
                    <td>${emp.lastName }</td>
                    <td>${emp.email }</td>
                    <td>${emp.gender == 0 ? 'Female' : 'Male' }</td>
                    <td>${emp.department.departmentName }</td>
                    <td><a href="emp/${emp.id}">Edit</a></td>
                    <%--添加--%>
                    <td><a class="delete" href="emp/${emp.id}">Delete</a></td>
                </tr>
            </c:forEach>
        </table>
    </c:if>
    <br><br>
    
    <a href="emp">Add New Employee</a>
    
    </body>
    </html>

*  handlers:Employee.java加入:

@RequestMapping(value = "/emp/{id}",method = RequestMethod.DELETE)
        public String delete(@PathVariable("id") Integer id){
            employeeDao.delete(id);
            return "redirect:/emps" ;
        }

删除后直接跳重定向到/emps 。

注意: 此时你会发现DELETE不行，这是因为引入jquery是静态资源。我们将 DispatcherServlet 请求映射配置为le /， Spring MVC会将捕获WEB 容器的所有请求，包括静态资源的请求， SpringMVC 会将他们当成一个普通请求处理，因找不到对应处理器将导致错误。

所以我们需要在springmvc.xml配置文件中加入:

<mvc:default-servlet-handler></mvc:default-servlet-handler>

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[Image 1]: 
[70]: /images/20220525/73fb68f7343841bd8da03f47538a67ea.png
[70 1]: /images/20220525/aa1b9dbbd7cf42ae90a0bb7d31c3013d.png
[SpringMVC 12.]: https://blog.csdn.net/hgx_suiyuesusu/article/details/80188284
[SpringMVC 14.]: https://blog.csdn.net/hgx_suiyuesusu/article/details/80200324