Spring MVC (6) spring MVC 写一个增删改查的小项目

2022年3月10日 69次阅读来源: qq_34334390

今天，在这里总结一下之前写过的一个对员工信息进行增删改查的小项目，首先，先将必要的环境搭建好，员工和部门的实体类以及对应的dao如下

部门实体类：

package com.tanla.springmvc.crud.entities;

public class Department {

    private Integer id;
    private String departmentName;

    public Department() {
        // TODO Auto-generated constructor stub
    }

    public Department(int i, String string) {
        this.id = i;
        this.departmentName = string;
    }

    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;
    }

    @Override
    public String toString() {
        return "Department [id=" + id + ", departmentName=" + departmentName
                + "]";
    }

}

员工实体类：
其中有几个注解
@Past：验证的数据类型：java.util.Date，java.util.Calendar，Joda Time类库的日期类型
说明：验证注解的元素值（日期类型）比当前时间早
注解详情参见：http://www.cnblogs.com/easymind223/p/5841043.html

package com.tanla.springmvc.crud.entities;

import java.util.Date;

import javax.validation.constraints.Past;

import org.hibernate.validator.constraints.Email;
import org.hibernate.validator.constraints.NotEmpty;
import org.springframework.format.annotation.DateTimeFormat;
import org.springframework.format.annotation.NumberFormat;

public class Employee { 

    private Integer id;
    @NotEmpty
    private String lastName;

    @Email
    private String email;
    //1 male, 0 female
    private Integer gender;

    private Department department;

    @Past
    @DateTimeFormat(pattern="yyyy-MM-dd")
    private Date birth;

    @NumberFormat(pattern="#,###,###.#")
    private Float salary;

    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 Date getBirth() {
        return birth;
    }

    public void setBirth(Date birth) {
        this.birth = birth;
    }

    public Float getSalary() {
        return salary;
    }

    public void setSalary(Float salary) {
        this.salary = salary;
    }

    @Override
    public String toString() {
        return "Employee [id=" + id + ", lastName=" + lastName + ", email="
                + email + ", gender=" + gender + ", department=" + department
                + ", birth=" + birth + ", salary=" + salary + "]";
    }

    public Employee(Integer id, String lastName, String email, Integer gender,
            Department department) {
        super();
        this.id = id;
        this.lastName = lastName;
        this.email = email;
        this.gender = gender;
        this.department = department;
    }

    public Employee() {
        // TODO Auto-generated constructor stub
    }
}

dao层：

package com.tanla.springmvc.crud.dao;

import java.util.Collection;
import java.util.HashMap;
import java.util.Map;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Repository;

import com.tanla.springmvc.crud.entities.Department;
import com.tanla.springmvc.crud.entities.Employee;

@Repository
public class EmployeeDao { 

    private static Map<Integer, Employee> employees = null;

    @Autowired
    private DepartmentDao departmentDao;

    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);
    }
}

package com.tanla.springmvc.crud.dao;

import java.util.Collection;
import java.util.HashMap;
import java.util.Map;

import org.springframework.stereotype.Repository;

import com.tanla.springmvc.crud.entities.Department;

@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);
    }

}

然后，把Spring mvc的环境搭建好，注意：在web.xml中添加如下拦截器，实现将post请求变成delete或者put请求

<!--配置filter将post请求变成 delete，put请求 -->
    <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>

接下来，说一说这个小项目实现的功能，以及它的流程。
第一步，新建一个index.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
   <!-- 此处加斜杠的时候 点进去的路径为http://localhost:8080/emps 不加斜杠的是http://localhost:8080/springMVC-2/emps -->
   <a href="emps">Get All Employee</a>
</body>
</html>

第二步，为这个页面的超链接写一个处理方法，新建一个类，名为EmployeeHandler，在里面写一个方法，其中的返回值对应的是一个jsp视图，名为list

@RequestMapping("/emps")
    public String list(Map<String, Object> map) {

        map.put("employees", employeeDao.getAll());
        return "list";
    }

第三步，根据Springmvc.xml中的配置信息来创建视图，在本例中，Springmvc.xml是如下配置的，说明所有在EmployeeHandler类中的处理方法返回的视图都在/WEB-INF/views/路径下。所以新建一个list.jsp来显示所有的员工信息

 <context:component-scan base-package="com.tanla.springmvc.crud"></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>

list.jsp：

<c:if test="${empty requestScope.employees }">
               没有员工信息
    </c:if>

    <c:if test="${!empty requestScope.employees }">
      <table border="1" cellpadding="10" cellspacing="0">
         <tr>
           <td>ID</td>
           <td>LAST NAME</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>

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

第四步，写一个添加新员工的功能。，点击list.jsp上面的添加新员工按钮，就会到对应的handler类中的方法中，然后会跳转到input.jsp页面

@RequestMapping(value="/emp" , method = RequestMethod.GET)
    public String input(Map<String ,Object> maps) {
            //将部门信息从数据库中读出来方便表单回显
        maps.put("departments",departmentDao.getDepartments() );
        //表单显示的时候，域对象里面必须有一个与表单字段对应的bean
        maps.put("employee", new Employee());
        return "input";
    }

input.jsp中应注意事项：
1）action中的路径必须加${pageContext.request.contextPath }
2）页面中的属性必须和实体类中的属性一一对应。

<%@page import="java.util.HashMap"%>
<%@page import="java.util.Map"%>
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>

  <form:form action="${pageContext.request.contextPath }/emp" method="POST" modelAttribute="employee">
    <!--根据这个来判断是添加操作还是编辑操作-->
    <c:if test="${employee.id == null }">
      LastName:<form:input path="lastName" />
    </c:if>

    <c:if test="${employee.id != null }">
      <form:hidden path="id"/>
      <input type="hidden" name="_method" value="PUT"/>
    </c:if>
    <br><br>
    Email:<form:input path="email"/>
    <br><br>
    <% Map<Integer , String> genders = new HashMap<Integer,String>(); genders.put(1, "male"); genders.put(0, "female"); request.setAttribute("genders",genders); %>
    Gender:<form:radiobuttons path="gender" items="${genders }"/>
    <br><br>
    Department:<form:select path="department.id" items="${departments }" itemLabel="departmentName" itemValue="id"></form:select>
    <br><br>
    <input type="submit" value="Submit">

  </form:form>

</body>
</html>

第五步，点击提交之后，会根据提交方法转到save方法中

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

第六步，删除操作
list.jsp页面上应该添加如下代码

<form action="" method="post">
        <input type="hidden" name="_method" value="DELETE">
    </form>

<script type="text/javascript"> $(function(){  $(".delete").click(function(){  var href = $(this).attr("href"); $("form").attr("action",href).submit(); return false; }); }) </script>

为了让静态页面有效果，必须在springmvc.xml配置文件中添加：

 <!-- 可以在 SpringMVC 的配置文件中配置 <mvc:default-servlet-handler/> 的方式解决静态资源的问题： <mvc:default-servlet-handler/> 将在 SpringMVC 上下文中定义一个 – DefaultServletHttpRequestHandler，它会对进入 DispatcherServlet 的 请求进行筛查，如果发现是没有经过映射的请求，就将该请求交由 WEB 应用服务器默认的 Servlet 处理， 如果不是静态资源的请求，才由DispatcherServlet 继续处理一般 WEB 应用服务器默认的 Servlet 的名称都是 default。 若所使用的 WEB 服务器的默认 Servlet 名称不是 default，则需要通过 default-servlet-name 属性显式指定 -->

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

@RequestMapping(value="/emp/{id}",method = RequestMethod.DELETE)
    public String delete(@PathVariable("id") Integer id) {

        employeeDao.delete(id);
        return "redirect:/emps";
    }

第七步，修改操作
注意事项：要在handler类中加入如下方法，因为在页面上没有lastName属性，所以不能直接去页面上的值，会导致lastName为空，应该先把数据从数据库中取出来，然后再用页面上的值覆盖它，保证没有修改的值也不会为空。

@ModelAttribute
    public void getEmployee(@RequestParam(value="id",required=false)Integer id,
            Map<String ,Object> maps) {
        if(id!=null) {
            maps.put("employee", employeeDao.get(id));
        }
    }

@RequestMapping(value="/emp",method=RequestMethod.PUT)
    public String update(Employee employee) {
        employeeDao.save(employee);
        return "redirect:/emps";
    }

    原文作者：qq_34334390
    原文地址: https://blog.csdn.net/qq_34334390/article/details/77680320
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