springboot中controller的使用

一、知识点

1	@Controller	处理http请求（不推荐使用）
2	@RestController	spring4之后新加的注解，原来返回json需要@ResponseBody配合@Controller
3	@RequestMapping	配置Url映射
4	@GetMapping	当 在方法上的注释时@RequestMapping的简化版，推荐使用，类似的还有@PostMapping等等
5	@RequestParam	映射请求参数到java方法的参数
6	@PageableDefault	指定分页参数默认值
7	@RequestBody	注解用于将Controller的方法参数，根据HTTP Request Header的content-Type的内容,通过适当的HttpMessageConverter转换为JAVA类

二、具体使用讲解

1.@Controller（了解即可，现在的开发基本都是前后端分离，不用再使用模版的方式，采用REST方式返回json数据是主流）

需要配合模版的使用

1）打开pom.xml

添加spring官方的一个模版thymeleaf

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
        </dependency>

2）在resources下新建文件夹templates，然后在其中新建一个html，index.html

<h1>hello spring boot!</h1>

3）controller中将@RestController改为@Controller

package com.dechy.girl.girl;
 
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
 
@Controller
public class HelloController {
 
    @Autowired
    private GirlProperties girlProperties;
 
    @RequestMapping(value = "/hello", method = RequestMethod.GET)
    public String say (){
        return "index";
    }
}

4）启动后，访问得到index.html的内容

2.@RestController

他是@Controller和@ResponseBody的组合

1）修改controller文件

package com.dechy.girl.girl;
 
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;
 
@Controller
@ResponseBody
public class HelloController {
 
    @Autowired
    private GirlProperties girlProperties;
 
    @RequestMapping(value = "/hello", method = RequestMethod.GET)
    public String say (){
        return girlProperties.getCupSize();
    }
}

此处为了简便，采用@RestController即可

3.@RequestMapping

1）可以设置映射多个地址，这样访问多个地址能可以返回相同的内容，例如

package com.dechy.girl.girl;
 
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
 
@RestController
public class HelloController {
 
    @Autowired
    private GirlProperties girlProperties;
 
    @RequestMapping(value = {"/hello","/hi"}, method = RequestMethod.GET)
    public String say (){
        return girlProperties.getCupSize();
    }
}

2）可以给整个类映射一个url，如下， 访问http://127.0.0.1:8082/hello/say即可

    package com.dechy.girl.girl;
 
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.beans.factory.annotation.Value;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RequestMethod;
    import org.springframework.web.bind.annotation.RestController;
 
    @RestController
    @RequestMapping("/hello")
    public class HelloController {
 
        @Autowired
        private GirlProperties girlProperties;
 
        @RequestMapping(value = "/say", method = RequestMethod.GET)
        public String say (){
            return girlProperties.getCupSize();
        }
    }

3）处理url的参数

@PathVariable	获取url中的数据
@RequestParam	获取请求参数的值
@GetMapping	组合注解
@PageableDefault	指定分页参数默认值

i)@PathVariable

    package com.dechy.girl.girl;
 
    import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
 
    @RestController
    @RequestMapping("/hello")
    public class HelloController {
 
        @Autowired
        private GirlProperties girlProperties;
 
        @RequestMapping(value = "/say/{id}", method = RequestMethod.GET)
        public String say (@PathVariable("id") Integer id){
            return "id:"+id;
        }
    }

或者改成

 @RequestMapping(value = "/{id}/say", method = RequestMethod.GET)

ii)@RequestParam

对于传统的url.如http://127.0.0.1:8082/hello/say?id=111

    package com.dechy.girl.girl;
 
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.*;
 
    @RestController
    @RequestMapping("/hello")
    public class HelloController {
 
        @Autowired
        private GirlProperties girlProperties;
 
        @RequestMapping(value = "/say", method = RequestMethod.GET)
        public String say (@RequestParam("id") Integer myId){
            return "id:"+myId;
        }
    }

其中黄色的不用一直，id对应的是url中的参数，myId可以自定义

另外，可以给@RequestParam设置默认值

    package com.dechy.girl.girl;
 
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.*;
 
    @RestController
    @RequestMapping("/hello")
    public class HelloController {
 
        @Autowired
        private GirlProperties girlProperties;
 
        @RequestMapping(value = "/say", method = RequestMethod.GET)
        public String say (@RequestParam(value="id",required = false,defaultValue = "0") Integer myId){
            return "id:"+myId;
        }
    }

iii)@GetMapping（推荐）

用@RequestParam的话，感觉代码太长，那么就可以使用@GetMapping，另外还可以有@PostMapping @PutMapping等等

    package com.dechy.girl.girl;
 
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.*;
 
    @RestController
    @RequestMapping("/hello")
    public class HelloController {
 
        @Autowired
        private GirlProperties girlProperties;
 
       @GetMapping(value="/say")
        public String say (@RequestParam(value="id",required = false,defaultValue = "0") Integer myId){
            return "id:"+myId;
        }
    }

iiii）@PageableDefault

指定指定分页参数默认值。

 @RequestMapping(value = "/user",method = RequestMethod.GET)
    public List<User> query(UserQueryCondition userQueryCondition, @PageableDefault(page=1,size=10,sort="username,asc") Pageable pageable){
        System.out.println(pageable.getPageNumber());
        System.out.println(pageable.getSort());
        System.out.println(pageable.getPageSize());
        System.out.println(userQueryCondition.toString());
        List<User> users=new ArrayList<>();
        users.add(new User());
        users.add(new User());
        users.add(new User());
        return  users;
    }

备注：此处Pageable需要引入如下依赖

<dependency>
     <groupId>org.springframework.data</groupId>
     <artifactId>spring-data-jpa</artifactId>
</dependency>