Day25 SpringMVC return value type is Object json processing

The return value of the processor-json data processing

1. When will json be used?

ajax request

2. Convert between javaBean object and json, such as:阿里巴巴的fastjson

pom.xml

     <dependency>
          <groupId>com.alibaba</groupId>
          <artifactId>fastjson</artifactId>
          <version>1.2.74</version>
      </dependency>
      <dependency>
          <groupId>junit</groupId>
          <artifactId>junit</artifactId>
          <version>4.12</version>
          <scope>test</scope>
      </dependency>

TestPersnoToJson

import com.alibaba.fastjson.JSON;
import org.junit.Test;

public class TestPersnoToJson {
    
    
    @Test
    public void  test01(){
    
    
        Person p = new Person(1,"jack","1234");
        String json  =  JSON.toJSONString(p);//调用静态方法toJSONString，参数传入对象 ，将对象转成json
        System.out.println(json);//{"id":1,"password":"1234","username":"jack"}
    }
    @Test
    public void  test02(){
    
    
        String json = "{\"id\":1,\"password\":\"1234\",\"username\":\"jack\"}";
        Person p = JSON.parseObject(json,Person.class);//json转javaBean，参1，json  参2 类
        System.out.println(p);//Person{id=1, username='jack', password='1234'}
    }
}

3. Convert the return value to json @ResponseBody

Notes added to the method, SpringMVC can automatically method returns an object into json, 发送给页面.
pom.xml
depends on jackson library

  <dependency>
          <groupId>com.fasterxml.jackson.core</groupId>
          <artifactId>jackson-databind</artifactId>
          <version>2.11.3</version>
      </dependency>

Demo02ReturnController

	@RequestMapping("demo05.action")
    //注解 @ResponseBody
    //注解加在方法上，SpringMVC可以自动将方法的返回对象转为json，发送给页面
    public @ResponseBody Object test05(){
    
    
        Person p1 = new Person(1,"jack","1234");
        Person p2 = new Person(2,"rose","1234");

        List<Person> list = new ArrayList<Person>();
        list.add(p1);
        list.add(p2);
        
        return list;//springmvc将 list使用ObjectMapper转成json
    }

4. Parameter to json @RequestBody

Add the @RequestBody annotation in front of the formal parameter. This annotation can automatically parse the json data sent from the page 将json中的数据封装到形参对象. After the analysis is completed, it will be automatically .

pom.xml
depends on jackson library

  <dependency>
          <groupId>com.fasterxml.jackson.core</groupId>
          <artifactId>jackson-databind</artifactId>
          <version>2.11.3</version>
      </dependency>

Demo02ReturnController

	@RequestMapping("demo06.action")
    //参数转json @RequestBody
    //在形参的前边加上@RequestBody注解，该注解可以自动解析页面发送过来的json数据，解析完之后，自动的将json中的数据封装到形参对象
    public ModelAndView test06(@RequestBody Person person){
    
    //使用Postman传数据进行测试
        System.out.println("object:"+person);
        return null;
    }

Use Postman to send json data to the server for

console printing