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><!-- https://mvnrepository.com/artifact/org.springframework/spring-webmvc --><dependency><groupId>org.springframework</groupId><artifactId>spring-webmvc</artifactId><version>5.0.3.RELEASE</version></dependency><!-- https://mvnrepository.com/artifact/javax.servlet/javax.servlet-api --><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"><!--编码过滤器--><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><!--配置org.springframework.web.filter.HiddenHttpMethodFilter:可以把POST请求转为DELETE　或　POST　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><servlet><servlet-name>springDispatcherServlet</servlet-name><servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class><!--配置DispatcherServlet初始化参数：springMVC配置文件的位置和参数--><!--也可以不通过contextConfigLocation来配置springMVC的配置文件，而使用默认的配置文件: /WEB-INF/views/<servlet-name>-servlet.xml即:springDispatcherServlet-servlet.xml--><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"><!--配置自动扫描的包--><context:component-scan base-package="com.ifox"></context:component-scan><!--配置视图解析器:如何把handler 方法返回值解析为实际的物理视图--><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;@Autowiredprivate 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() {}@Overridepublic 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;}@Overridepublic 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

1.1 handlers

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

1.2 index.jsp

 <a href="/emps">list page</a>

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:

<!-- https://mvnrepository.com/artifact/javax.servlet/jstl --><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 MapitemValue：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="&nbsp;&nbsp;"></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。

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:

<td><a href="emp/${emp.id}">Edit</a></td>

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。
注意我们在web.xml中加入的：

 <!--配置org.springframework.web.filter.HiddenHttpMethodFilter:可以把POST请求转为DELETE　或　POST　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>

handlers:EmployeeHandler.java中添加:

@ModelAttributepublic 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="&nbsp;&nbsp;"></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:

<!-- https://mvnrepository.com/artifact/javax.servlet/jstl --><dependency><groupId>javax.servlet</groupId><artifactId>jstl</artifactId><version>1.2</version></dependency>

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:
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:

 <!--静态资源处理--><mvc:default-servlet-handler></mvc:default-servlet-handler>

上一篇:SpringMVC 12. 重定向
下一篇:SpringMVC 14. 处理静态资源

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