REST全称Representation State Transfer，表现形式状态转换

1. 为什么提出了REST？

传统风格资源描述形式：

• http://localhost/user/getById?id=1
• http://localhost/user/saveUser

REST风格描述形式：

• http://localhost/user/1
• http://localhost/user

REST风格优点：

• 隐藏资源的访问行为，无法通过地址得知对资源是何种操作（REST风格描述的第二项既可以描述一个saveUser操作，也可以描述一个updateUser操作）
• 书写简化

按照REST风格访问资源时使用行为动作区分对资源进行了何种操作，根据REST风格对资源进行访问称为RESTful

地址	作用	行为动作
http://localhost/users	查询全部用户信息	GET (查询)
http://localhost/user/1	查询指定用户信息	GET (查询)
http://localhost/users	添加用户信息	POST (新增/保存)
http://localhost/users	修改用户信息	PUT (修改/更新)
http://localhost/users/1	删除用户信息	DELETE (删除)

注： 上述行为是约定方式，约定不是规范，可以打破，所以称REST风格，而不是REST规范
描述模块的名称通常使用复数，也就是加s的格式描述，表示此类资源，而非单个资源，例如：users、books、accounts…

2. RESTful入门案例

案例代码

config/ServletContainerInitConfig.java

package com.demo.config;import org.apache.ibatis.jdbc.Null;
import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.AnnotationConfigWebApplicationContext;
import org.springframework.web.filter.CharacterEncodingFilter;
import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;
import org.springframework.web.servlet.support.AbstractDispatcherServletInitializer;import javax.servlet.Filter;public class ServletContainerInitConfig extends AbstractAnnotationConfigDispatcherServletInitializer {@Overrideprotected Class<?>[] getRootConfigClasses() {return new Class[0];}@Overrideprotected Class<?>[] getServletConfigClasses() {return new Class[]{SpringMvcConfig.class};}@Overrideprotected String[] getServletMappings() {return new String[]{"/"};}@Overrideprotected Filter[] getServletFilters() {CharacterEncodingFilter filter = new CharacterEncodingFilter();filter.setEncoding("UTF-8");return new Filter[]{filter};}
}

config/SpringMvcConfig.java

package com.demo.config;import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;@Configuration
@ComponentScan("com.demo.controller")
@EnableWebMvc
public class SpringMvcConfig {
}

controller/BookController.java

package com.demo.controller;import com.demo.domain.Book;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;@Controller
public class BookController {@RequestMapping(value = "/books", method = RequestMethod.POST)@ResponseBodypublic String save(@RequestBody Book book){System.out.println("book save ...");return "{'module': 'book save'}";}@RequestMapping(value = "/books", method = RequestMethod.DELETE)@ResponseBodypublic String delete(@PathVariable Integer id){System.out.println("book delete ..." + id);return "{'module': 'book delete'}";}@RequestMapping(value = "/books", method = RequestMethod.PUT)@ResponseBodypublic String update(@RequestBody Book book){System.out.println("book update ..." + book);return "{'module': 'book update'}";}@RequestMapping(value = "/books/{id}", method = RequestMethod.GET)@ResponseBodypublic String getById(@PathVariable Integer id){System.out.println("book getById ..." + id);return "{'module': 'book getById'}";}@RequestMapping(value = "/books", method = RequestMethod.GET)@ResponseBodypublic String getAll(){System.out.println("book getAll ...");return "{'module': 'book update'}";}
}

controller/UserController.java

package com.demo.controller;import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;@Controller
public class UserController {@RequestMapping("/save")@ResponseBodypublic String save(){System.out.println("User save...");return "{'module': 'springmvc'}";}@RequestMapping("/delete")@ResponseBodypublic String delete(Integer id){System.out.println("User delete..." + id);return "{'module': 'springmvc'}";}@RequestMapping("/update")@ResponseBodypublic String update(@RequestBody User user){System.out.println("User update... => " + user);return "{'module': 'springmvc'}";}
}

domain/User.java

package com.demo.domain;public class User {private String name;private int age;Address address;@Overridepublic String toString() {return "User{" +"name='" + name + '\'' +", age=" + age +", address=" + address +'}';}public Address getAddress() {return address;}public void setAddress(Address address) {this.address = address;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}
}

domain/Book.java

package com.demo.domain;public class Book {String bookName;String issn;@Overridepublic String toString() {return "Book{" +"bookName='" + bookName + '\'' +", issn='" + issn + '\'' +'}';}public String getBookName() {return bookName;}public void setBookName(String bookName) {this.bookName = bookName;}public String getIssn() {return issn;}public void setIssn(String issn) {this.issn = issn;}
}

修改请求方式

测试一下UserController中的三个方法：

修改成RESTful风格，并以POST方式提交

将两个方法上的@RequestMapping注解，均新增一个method属性，并修改value属性，如下：

@RequestMapping(value = "/users", method = RequestMethod.POST)
@RequestMapping(value = "/users", method = RequestMethod.DELETE)
@RequestMapping(value = "/users", method = RequestMethod.PUT)

再运行，发现可以运行（注意，Postman中请求的模式要记得修改）：

RESTful格式下传参

我们的delete方法中是有参数的，那在RESTful风格下，我们的路径是localhost/delete/1，那这个1怎么传到方法中的id里呢？
应该在路径后面接上{variable name}来表示我们想要传递的参数，这里variable name填写的应该是方法中的参数名；并在方法的参数前面使用@PathVariable注解声明该变量来自路径。例如：

@RequestMapping(value = "/users/{id}", method = RequestMethod.DELETE)
@ResponseBody
public String delete(@PathVariable Integer id){System.out.println("User delete..." + id);return "{'module': 'springmvc'}";
}

但对于像Update方法中这种传User这种POJO数据（注意 Integer不算POJO数据）的，则不需要做改动
修改后请求delete方法如下

请求update方法仍然是将JSON数据转换为POJO，

RESTful入门案例总结

想要使用RESTful风格，步骤如下：

1. 设定http请求动作（动词），如Request.POST, Request.PUT, Request.GET, Request.Delete等
2. 设定请求参数（路径变量），在请求路径中使用{variable name}添加请求参数，方法中的参数前使用@PathVariable进行注解

@RequestBody，@RequestParam，@PathVariable总结

区别：

• @RequestBody用于接收JSON数据
• @RequestParam用于接收url地址或表单传参
• @PathVariable用于接收路径参数，使用{参数名称}描述路径参数

应用：

• 后期开发中，发送请求参数超过1个时，以JSON格式为主，@RequestBody应用较广
• 发送非JSON格式数据，选用@RequestParam接收请求参数
• 采用RESTful开发，当参数量较少时，例如1个，可以采用@PathVariable接收请求路径变量，通常用于传递id值。当然也可以通过@PathVariable注解接收多个请求路径变量，但多个变量主要还是用JSON

3. RESTful快速开发

入门案例中存在一个问题，如下（下边以BookController为例讲解），红框中内容重复，应该简化掉：

第一次修改

针对于这个问题，我们首先可以将@RequestMapping作为类注解写在类上，@ResponseBody也可以作为类注解写在类上。但有一个更简便的办法：@RestController注解包含了@Controller和@ResponseBody，最终修改如下：

package com.demo.controller;import com.demo.domain.Book;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;@RequestMapping("books")
@RestController
public class BookController {@RequestMapping(method = RequestMethod.POST)public String save(@RequestBody Book book){System.out.println("book save ...");return "{'module': 'book save'}";}@RequestMapping(method = RequestMethod.DELETE)public String delete(@PathVariable Integer id){System.out.println("book delete ..." + id);return "{'module': 'book delete'}";}@RequestMapping(method = RequestMethod.PUT)public String update(@RequestBody Book book){System.out.println("book update ..." + book);return "{'module': 'book update'}";}@RequestMapping(method = RequestMethod.GET)public String getById(@PathVariable Integer id){System.out.println("book getById ..." + id);return "{'module': 'book getById'}";}@RequestMapping(method = RequestMethod.GET)public String getAll(){System.out.println("book getAll ...");return "{'module': 'book update'}";}
}

第二次修改

修改完以后，代码里又存在大量的@RequestMapping(method=...)，也挺冗余的，可以做如下修改：
将@RequestMapping(method = RequestMethod.xxx)替换成@xxxMapping
如果在@RequestMapping中还有表示参数的value，就在@xxxMapping后加上(参数路径)，比如@xxxMapping("/{id}")。
所有代码再次修改如下：

package com.demo.controller;import com.demo.domain.Book;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;@RequestMapping("books")
@RestController
public class BookController {@PostMappingpublic String save(@RequestBody Book book){System.out.println("book save ...");return "{'module': 'book save'}";}@DeleteMapping("/{id}")public String delete(@PathVariable Integer id){System.out.println("book delete ..." + id);return "{'module': 'book delete'}";}@PutMappingpublic String update(@RequestBody Book book){System.out.println("book update ..." + book);return "{'module': 'book update'}";}@GetMapping("/{id}")public String getById(@PathVariable Integer id){System.out.println("book getById ..." + id);return "{'module': 'book getById'}";}@GetMappingpublic String getAll(){System.out.println("book getAll ...");return "{'module': 'book update'}";}
}

逐项进行测试：

控制台输出：

快速开发注解总结

1. @RestController：类注解，在控制器类上方进行定义，设置当前控制器为RESTful风格，等同于@Controller和@ResponseBody两个注解组合功能
2. @GetMapping,@PostMapping,@PutMapping,@DeleteMapping：方法注解，注解在SpringMVC的RESTful开发控制器方法上方，其作用是设置当前控制器方法访问路径与请求动作，每种对应一个请求动作

4. RESTful案例开发

我们在这个案例下的目标是通过RESTful实现案例交互：发送RESTful请求，获取数据后在页面中展示结果

案例代码（一些config的设定和domain等）

config/SevletContainerInitConfig.java

package com.demo.config;import org.apache.ibatis.jdbc.Null;
import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.AnnotationConfigWebApplicationContext;
import org.springframework.web.filter.CharacterEncodingFilter;
import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;
import org.springframework.web.servlet.support.AbstractDispatcherServletInitializer;import javax.servlet.Filter;public class ServletContainerInitConfig extends AbstractAnnotationConfigDispatcherServletInitializer {@Overrideprotected Class<?>[] getRootConfigClasses() {return new Class[0];}@Overrideprotected Class<?>[] getServletConfigClasses() {return new Class[]{SpringMvcConfig.class};}@Overrideprotected String[] getServletMappings() {return new String[]{"/"};}@Overrideprotected Filter[] getServletFilters() {CharacterEncodingFilter filter = new CharacterEncodingFilter();filter.setEncoding("UTF-8");return new Filter[]{filter};}
}

config/SpringMvcConfig.java

package com.demo.config;import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;@Configuration
@ComponentScan("com.demo.controller")
@EnableWebMvc
public class SpringMvcConfig {
}

domain/Book.java

package com.demo.domain;public class Book {private Integer id;private String type;private String name;private String description;@Overridepublic String toString() {return "Book{" +"id=" + id +", type='" + type + '\'' +", name='" + name + '\'' +", description='" + description + '\'' +'}';}public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public String getType() {return type;}public void setType(String type) {this.type = type;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getDescription() {return description;}public void setDescription(String description) {this.description = description;}
}

后台Controller的开发

写一个save方法和一个getAll方法

package com.demo.controller;import com.demo.domain.Book;
import org.springframework.web.bind.annotation.*;import java.util.ArrayList;
import java.util.List;@RestController
@RequestMapping("/books")
public class BookController {@PostMappingpublic String save(@RequestBody Book book){System.out.println("book save ==> " + book);return "{'module':'book save success'}";}@GetMappingpublic List<Book> getAll(){Book book1 = new Book();book1.setType("计算机");book1.setName("SpringMVC1111");book1.setDescription("小试牛刀");Book book2 = new Book();book2.setType("计算机");book2.setName("SpringMvc2222");book2.setDescription("一代宗师");List<Book> bookList = new ArrayList<>();bookList.add(book1);bookList.add(book2);return bookList;}}

启动Tomcat容器进行测试


前端使用了ElementUI+Vue，但是我目前不太记得这个东西了（等我弄清楚了再来这里补充），可以先转去视频，里边有很详细的介绍完整的案例开发：Bilibili-基于RESTful的页面数据交互