RESTFul

RESTFul简介

REST：Representational State Transfer，表现层资源状态转移。

a>资源

资源是一种看待服务器的方式，即，将服务器看作是由很多离散的资源组成。每个资源是服务器上一个可命名的抽象概念。因为资源是一个抽象的概念，所以它不仅仅能代表服务器文件系统中的一个文件、数据库中的一张表等等具体的东西，可以将资源设计的要多抽象有多抽象，只要想象力允许而且客户端应用开发者能够理解。与面向对象设计类似，资源是以名词为核心来组织的，首先关注的是名词。一个资源可以由一个或多个URI来标识。URI既是资源的名称，也是资源在Web上的地址。对某个资源感兴趣的客户端应用，可以通过资源的URI与其进行交互。

b>资源的表述

资源的表述是一段对于资源在某个特定时刻的状态的描述。可以在客户端-服务器端之间转移（交换）。资源的表述可以有多种格式，例如HTML/XML/JSON/纯文本/图片/视频/音频等等。资源的表述格式可以通过协商机制来确定。请求-响应方向的表述通常使用不同的格式。

c>状态转移

状态转移说的是：在客户端和服务器端之间转移（transfer）代表资源状态的表述。通过转移和操作资源的表述，来间接实现操作资源的目的。

RESTful的实现

具体说，就是 HTTP 协议里面，四个表示操作方式的动词：GET、POST、PUT、DELETE。

它们分别对应四种基本操作：GET 用来获取资源，POST 用来新建资源，PUT 用来更新资源，DELETE 用来删除资源。

REST 风格提倡 URL 地址使用统一的风格设计，从前到后各个单词使用斜杠分开，不使用问号键值对方式携带请求参数，而是将要发送给服务器的数据作为 URL 地址的一部分，以保证整体风格的一致性。

操作	传统方式	REST风格
查询操作	getUserById?id=1	user/1-->get请求方式
保存操作	saveUser	user-->post请求方式
删除操作	deleteUser?id=1	user/1-->delete请求方式
更新操作	updateUser	user-->put请求方式

HiddenHttpMethodFilter

由于浏览器只支持发送get和post方式的请求，那么该如何发送put和delete请求呢？

SpringMVC 提供了 HiddenHttpMethodFilter 帮助我们将 POST 请求转换为 DELETE 或 PUT 请求

HiddenHttpMethodFilter 处理put和delete请求的条件：

a>当前请求的请求方式必须为post

b>当前请求必须传输请求参数_method

满足以上条件，HiddenHttpMethodFilter 过滤器就会将当前请求的请求方式转换为请求参数_method的值，因此请求参数_method的值才是最终的请求方式

在web.xml中注册HiddenHttpMethodFilter

<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>

tips：
目前为止，SpringMVC中提供了两个过滤器：CharacterEncodingFilter和HiddenHttpMethodFilter
在web.xml中注册时，必须先注册CharacterEncodingFilter，再注册HiddenHttpMethodFilter
原因：
在 CharacterEncodingFilter 中通过 request.setCharacterEncoding(encoding) 方法设置字符集的
request.setCharacterEncoding(encoding) 方法要求前面不能有任何获取请求参数的操作
而 HiddenHttpMethodFilter 恰恰有一个获取请求方式的操作：
1
String paramValue = request.getParameter(this.methodParam);

完整代码：

@Controller
public class UserController {

    /**
     * 使用RESTFul模拟用户资源的增删改查
     * /user    GET       查询所有用户信息
     * /user/1  GET       根据用户ID查询所有用户信息
     * /user    POST      添加用户信息
     * /user/1  DELETE    删除用户信息
     * /user    PUT       修改用户信息
     */

    @RequestMapping(value = "/user",method = RequestMethod.GET )
    public String getAllUser(){
        System.out.println("查询所有用户信息");
        return "success";
    }

    @RequestMapping(value = "/user/{id}",method=RequestMethod.GET)
    public String getUserById(){
        System.out.println("根据ID查询用户信息");
        return "success";
    }

    @RequestMapping(value = "/user",method = RequestMethod.POST)
    public String insertUser(String username,String password){
        System.out.println("添加用户信息:"+username+","+password);
        return "success";
    }

    @RequestMapping(value = "/user",method = RequestMethod.PUT)
    public String updateUser(String username,String password){
        System.out.println("修改用户信息:"+username+","+password);
        return "success";

    }


}

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<a th:href="@{/user}">查询所有用户信息</a><br>
<a th:href="@{/user/1}">根据Id查询用户信息</a><br>
<form th:action="@{/user}" method="post">
    用户名:<input type="text" name="username"><br>
    密码:<input type="password" name="password"><br>
    <input type="submit" name="添加"><br>
</form><br>

<form th:action="@{/user}" method="post">
    <input type="hidden " name="_method" value="PUT"><br>
    用户名:<input type="text" name="username"><br>
    密码:<input type="password" name="password"><br>
    <input type="submit" name="修改"><br>
</form><br>

<form th:action="@{/user}" method="post">
    <input type="hidden " name="_method" value="DELETE"><br>
    用户名:<input type="text" name="username"><br>
    密码:<input type="password" name="password"><br>
    <input type="submit" name="删除"><br>
</form>

</body>
</html>

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
success<br>
<p th:text="${testRequestScope}"></p>
<p th:text="${session.testSessionScope}"></p>
</body>
</html>

访问URL

控制台
添加用户信息

修改用户信息

RESTful案例

准备工作

和传统 CRUD 一样，实现对员工信息的增删改查。

搭建环境

准备实体类

package com.atguigu.mvc.bean;

public class Employee {

   private Integer id;
   private String lastName;

   private String email;
   //1 male, 0 female
   private Integer gender;
   
   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 Employee(Integer id, String lastName, String email, Integer gender) {
      super();
      this.id = id;
      this.lastName = lastName;
      this.email = email;
      this.gender = gender;
   }

   public Employee() {
   }
}

准备dao模拟数据

package com.atguigu.mvc.dao;

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

import com.atguigu.mvc.bean.Employee;
import org.springframework.stereotype.Repository;


@Repository
public class EmployeeDao {

   private static Map<Integer, Employee> employees = null;
   
   static{
      employees = new HashMap<Integer, Employee>();

      employees.put(1001, new Employee(1001, "E-AA", "aa@163.com", 1));
      employees.put(1002, new Employee(1002, "E-BB", "bb@163.com", 1));
      employees.put(1003, new Employee(1003, "E-CC", "cc@163.com", 0));
      employees.put(1004, new Employee(1004, "E-DD", "dd@163.com", 0));
      employees.put(1005, new Employee(1005, "E-EE", "ee@163.com", 1));
   }
   
   private static Integer initId = 1006;
   
   public void save(Employee employee){
      if(employee.getId() == null){
         employee.setId(initId++);
      }
      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);
   }
}

功能清单

功能	URL 地址	请求方式
访问首页√	/	GET
查询全部数据√	/employee	GET
删除√	/employee/2	DELETE
跳转到添加数据页面√	/toAdd	GET
执行保存√	/employee	POST
跳转到更新数据页面√	/employee/2	GET
执行更新√	/employee	PUT

具体功能：访问首页

a>配置view-controller

1	`<mvc:view-controller path="/" view-name="index"/>`

b>创建页面

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8" >
    <title>Title</title>
</head>
<body>
<h1>首页</h1>
<a th:href="@{/employee}">访问员工信息</a>
</body>
</html>

具体功能：查询所有员工数据

a>控制器方法

@RequestMapping(value = "/employee", method = RequestMethod.GET)
public String getEmployeeList(Model model){
    Collection<Employee> employeeList = employeeDao.getAll();
    model.addAttribute("employeeList", employeeList);
    return "employee_list";
}

b>创建employee_list.html

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>Employee Info</title>
    <script type="text/javascript" th:src="@{/static/js/vue.js}"></script>
</head>
<body>

    <table border="1" cellpadding="0" cellspacing="0" style="text-align: center;" id="dataTable">
        <tr>
            <th colspan="5">Employee Info</th>
        </tr>
        <tr>
            <th>id</th>
            <th>lastName</th>
            <th>email</th>
            <th>gender</th>
            <th>options(<a th:href="@{/toAdd}">add</a>)</th>
        </tr>
        <tr th:each="employee : ${employeeList}">
            <td th:text="${employee.id}"></td>
            <td th:text="${employee.lastName}"></td>
            <td th:text="${employee.email}"></td>
            <td th:text="${employee.gender}"></td>
            <td>
                <a class="deleteA" @click="deleteEmployee" th:href="@{'/employee/'+${employee.id}}">delete</a>
                <a th:href="@{'/employee/'+${employee.id}}">update</a>
            </td>
        </tr>
    </table>
</body>
</html>

具体功能：删除

a>创建处理delete请求方式的表单

<!-- 作用：通过超链接控制表单的提交，将post请求转换为delete请求 -->
<form id="delete_form" method="post">
    <!-- HiddenHttpMethodFilter要求：必须传输_method请求参数，并且值为最终的请求方式 -->
    <input type="hidden" name="_method" value="delete"/>
</form>

b>删除超链接绑定点击事件

引入vue.js

1	`<script type="text/javascript" th:src="@{/static/js/vue.js}"></script>`

删除超链接

1	`<a class="deleteA" @click="deleteEmployee" th:href="@{'/employee/'+${employee.id}}">delete</a>`

通过vue处理点击事件

<script type="text/javascript">
    var vue = new Vue({
        el:"#dataTable",
        methods:{
            //event表示当前事件
            deleteEmployee:function (event) {
                //通过id获取表单标签
                var delete_form = document.getElementById("delete_form");
                //将触发事件的超链接的href属性为表单的action属性赋值
                delete_form.action = event.target.href;
                //提交表单
                delete_form.submit();
                //阻止超链接的默认跳转行为
                event.preventDefault();
            }
        }
    });
</script>

c>控制器方法

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

具体功能：跳转到添加数据页面

a>配置view-controller

1	`<mvc:view-controller path="/toAdd" view-name="employee_add"></mvc:view-controller>`

b>创建employee_add.html

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>Add Employee</title>
</head>
<body>

<form th:action="@{/employee}" method="post">
    lastName:<input type="text" name="lastName"><br>
    email:<input type="text" name="email"><br>
    gender:<input type="radio" name="gender" value="1">male
    <input type="radio" name="gender" value="0">female<br>
    <input type="submit" value="add"><br>
</form>

</body>
</html>

具体功能：执行保存

>控制器方法

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

具体功能：跳转到更新数据页面

a>修改超链接

1	`<a th:href="@{'/employee/'+${employee.id}}">update</a>`

b>控制器方法

@RequestMapping(value = "/employee/{id}", method = RequestMethod.GET)
public String getEmployeeById(@PathVariable("id") Integer id, Model model){
    Employee employee = employeeDao.get(id);
    model.addAttribute("employee", employee);
    return "employee_update";
}

c>创建employee_update.html

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>Update Employee</title>
</head>
<body>

<form th:action="@{/employee}" method="post">
    <input type="hidden" name="_method" value="put">
    <input type="hidden" name="id" th:value="${employee.id}">
    lastName:<input type="text" name="lastName" th:value="${employee.lastName}"><br>
    email:<input type="text" name="email" th:value="${employee.email}"><br>
    <!--
        th:field="${employee.gender}"可用于单选框或复选框的回显
        若单选框的value和employee.gender的值一致，则添加checked="checked"属性
    -->
    gender:<input type="radio" name="gender" value="1" th:field="${employee.gender}">male
    <input type="radio" name="gender" value="0" th:field="${employee.gender}">female<br>
    <input type="submit" value="update"><br>
</form>

</body>
</html>

具体功能：执行更新

a>控制器方法

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

完整代码：

@Controller
public class EmployeeController {

    @Autowired
    private EmployeeDao employeeDao;

    @RequestMapping(value = "/employee",method = RequestMethod.GET)
    public String getAllEmployee(Model model){
        Collection<Employee> employeeList = employeeDao.getAll();
        model.addAttribute("employeeList",employeeList);
        return "Employee_list";

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

    }

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

    @RequestMapping(value = "/employee/{id}",method = RequestMethod.GET)
    public String getEmployeeById(@PathVariable("id") Integer id,Model model){
        Employee employee = employeeDao.get(id);
        model.addAttribute("employee",employee);
        return "Employee_update";
    }

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

    }
}

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>首页</title>
</head>
<body>
<h1>首页</h1>
<a th:href="@{/employee}">查看员工信息</a>
</body>
</html>

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>Employee-Info</title>
</head>
<body>

    <table id="dataTable" border="1" cellspacing="0" cellpadding="0" style="text-align:center">
        <tr>
            <th colspan="5">Employee Info</th>
        </tr>
        <tr>
            <th>id</th>
            <th>lastName</th>
            <th>email</th>
            <th>gender</th>
            <th>options(<a th:href="@{/toAdd}")>add</a>></th>
        </tr>
        <tr th:each="employee:${employeeList}">
            <td th:text="${employee.id}"></td>
            <td th:text="${employee.lastName}"></td>
            <td th:text="${employee.email}"></td>
            <td th:text="${employee.gender}"></td>
            <td>
                <a class="deleteA" @click="deleteEmployee" th:href="@{'/employee/'+${employee.id}}">delete</a>
                <a th:href="@{'/employee/'+${employee.id}}">update</a></a>
            </td>
        </tr>
    </table>
    <form id="deleteForm" method="post">
        <input type="hidden" name="_method" value="delete">
    </form>

    <script type="text/javascript" th:src="@{/static/js/vue.js}"></script>
    <script type="text/javascript">
        var vue=new Vue({
            el:"#dataTable",
            methods:{
                deleteEmployee:function (event){
                    //根据id获取表单元素
                    var deleteForm=document.getElementById("deleteForm");
                    //将触发点击事件的超链接的href属性赋值给表单的action
                    deleteForm.action=event.target.href;
                    //提交表单
                    deleteForm.submit();
                    //取消超链接的默认行为
                    event.preventDefault();
                }
            }

        })
    </script>
</body>
</html>

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>add Employee</title>
</head>
<body>
<form th:action="@{/employee}" method="post">
    lastName:<input type="text" name="lastName"><br>
    email:<input type="text" name="email"><br>
    gender:<input type="radio" name="gender" value="1">male
    <input type="radio" name="gender" value="0">female<br>
    <input type="submit" name="add"><br>
</form>
</body>
</html>

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>Update Employee</title>
</head>
<body>

<form th:action="@{/employee}" method="post">
    <input type="hidden" name="_method" value="put">
    <input type="hidden" name="id" th:value="${employee.id}">
    lastName:<input type="text" name="lastName" th:value="${employee.lastName}"><br>
    email:<input type="text" name="email" th:value="${employee.email}"><br>
    gender:<input type="radio" name="gender" value="1" th:field="${employee.gender}">male
    <input type="radio" name="gender" value="0" th:field="${employee.gender}">female<br>
    <input type="submit" value="update"><br>
</form>

</body>
</html>