【SpringMVC】7.REST风格的CRUD实战（一）之前期工作

##一、什么是REST和CRUD？

###1.有关REST
有关REST的解释我已近在之前的SpringMVC系列文章提到过，如果有兴趣的同学可以翻看《【SpringMVC】3.REST表现层状态转换》进行查看。

###2.有关CRUD

In computer programming, create, read, update, and delete(CRUD) are the four basic functions of persistent storage.Alternate words are sometimes used when defining the four basic functions of CRUD, such as retrieve instead of read, modify instead of update, or destroy instead of delete. CRUD is also sometimes used to describe user interface conventions that facilitate viewing, searching, and changing information; often using computer-based forms and reports. The term was likely first popularized by James Martin in his 1983 book Managing the Data-base Environment.[1][3] The acronym may be extended to CRUDL to cover listing of large data sets which bring additional complexity such as pagination when the data sets are too large to hold easily in memory.–维基百科《Create, read, update and delete》

在计算机编程中，创建，读取，更新和删除CRUD）是持久存储的四个基本功能。在定义CRUD的四个基本功能时，有时会使用替代词，例如检索而不是读取，修改而不是更新，或者销毁而不是删除。CRUD有时也用于描述便于查看，搜索和更改信息的用户界面约定; 经常使用基于计算机的表格和报告。詹姆斯·马丁（James Martin）在其1983年的“ 管理数据库环境”一书中首次推广该术语。首字母缩略词可以扩展到CRUDL，以涵盖大数据集的列表，当数据集太大而无法轻易保存在内存中时，这些数据集会带来额外的复杂性，例如分页。



##二、实战项目需求

###1.目标
使用REST和CRUD的方式来对数据进行增加，查询，修改，删除操作。
###2.相关接口
####显示所有员工信息

• URI：emps
• 请求方式：GET
• 显示效果
  

####显示添加页面

• URI：emp
• 请求方式：GET
• 显示效果
  

####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。

####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

####修改操作

• 显示修改页面
• URI：emp/{id}
• 请求方式：GET
• 显示效果：回显表单。

####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
  
  
  
  ##三、实战代码

---

###开发前需要准备的配置
####1.创建一个名为SpringMVC-2的新Web项目
####2.导入相关的JAR包


####3.配置web.xml文件

<?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">
	<!-- 配置springDispatcherServlet -->
	<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>

####4.配置src根目录下的springmvc.xml文件

<?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:mvc="http://www.springframework.org/schema/mvc"
	xmlns:context="http://www.springframework.org/schema/context"
	xsi:schemaLocation="http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.1.xsd
		http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.1.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.1.xsd">

	<!-- 配置自动扫描的包 -->
	<context:component-scan base-package="com.springmvc.crud"></context:component-scan>

	<!-- 配置视图解析器 -->
	<bean
		class="org.springframework.web.servlet.view.InternalResourceViewResolver">
		<property name="prefix" value="/WEB-INF/views/"></property>
		<property name="suffix" value=".jsp"></property>
	</bean>
</beans>

####5.在com.springmvc.crud.entities包中建立实体类Employee和Department

实体类Employee

package com.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
	}
}

实体类Department

package com.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
				+ "]";
	}
	
}

####6.在com.springmvc.crud.dao中创建Dao类EmployeeDao和DepartmentDao
注意！！！
由于由于连接数据库比较麻烦，所以在这里选择使用静态模拟从数据库中取出数据。

Dao类EmployeeDao

package com.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.springmvc.crud.entities.Department;
import com.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", "[email protected]", 1, new Department(101, "D-AA")));
		employees.put(1002, new Employee(1002, "E-BB", "[email protected]", 1, new Department(102, "D-BB")));
		employees.put(1003, new Employee(1003, "E-CC", "[email protected]", 0, new Department(103, "D-CC")));
		employees.put(1004, new Employee(1004, "E-DD", "[email protected]", 0, new Department(104, "D-DD")));
		employees.put(1005, new Employee(1005, "E-EE", "[email protected]", 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);
	}
}

Dao类DepartmentDao

package com.springmvc.crud.dao;

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

import org.springframework.stereotype.Repository;

import com.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);
	}
	
}

####7.在WebRoot/WEB-INF/views/下创建list.jsp和input.jsp

####8.在WebRoot根目录创建index.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>My JSP 'index.jsp' starting page</title>
  </head>
  
  <body>
   <a href="emps">Show all employee</a>
   
  
  </body>
</html>

###9.在com.springmvc.crud.handlers下创建Handler类EmployeeHandler