springboot2中JSON的使用（官网学习）

简介

Spring Boot提供了与三个JSON映射库的集成。分别是Gson、Jackson、JSON-B
Jackson是默认集成的

Jackson

Jackson的转换是通过ObjectMapper对象来实现的，spring boot内部自动配置了一个ObjectMapper对象
Jackson使用ObjectMapper序列化java对象，java类必须有一个默认的无参构造器

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class LawController {
    
    
    @RequestMapping("/test")
    public String test() throws JsonProcessingException {
    
    
        ObjectMapper objectMapper = new ObjectMapper();
        User user = new User("jerry", 1);
        // 序列化
        String json = objectMapper.writeValueAsString(user);
        // 返回{"name":"jerry","id":1}
        return json;
    }

    @RequestMapping("/test2")
    public User test2() throws JsonProcessingException {
    
    
        ObjectMapper objectMapper = new ObjectMapper();
        String json="{\"name\":\"jerry\",\"id\":1}";
        // 反序列化
        User user = objectMapper.readValue(json, User.class);
        // 返回 {"name":"jerry","id":1}
        return user;
    }
}

class User {
    
    
    private String name;
    private int id;
    public User(){
    
    

    }
    public String getName() {
    
    
        return name;
    }

    public void setName(String name) {
    
    
        this.name = name;
    }

    public int getId() {
    
    
        return id;
    }

    public void setId(int id) {
    
    
        this.id = id;
    }

    public User(String name, int id) {
    
    
        this.name = name;
        this.id = id;
    }

    @Override
    public String toString() {
    
    
        return "User{" +
                "name='" + name + '\'' +
                ", id=" + id +
                '}';
    }
}

打开浏览器访问http://localhost:8080/test,输出{“name”:“jerry”,“id”:1}；
打开浏览器访问http://localhost:8080/test2,输出{“name”:“jerry”,“id”:1}；

GSON

添加maven依赖

 <dependency>
            <groupId>com.google.code.gson</groupId>
            <artifactId>gson</artifactId>
            <version>2.9.0</version>
 </dependency>

java代码

import com.google.gson.Gson;

@SuppressWarnings({
    
    "all"})
public class GsonController {
    
    
    public static void main(String[] args) {
    
    
        Gson gson=new Gson();
        Student student=new Student("er","1");
        // 序列化，Student对象转换成json字符串
        String json=gson.toJson(student);
        System.out.println(json);//输出{"name":"er","no":"1"}
        // 反序列化，json字符串转换成Student对象
        Student student1=gson.fromJson(json,Student.class);
        System.out.println(student1);//输出Student{name='er', no='1'}
    }
}
class Student{
    
    
    private String name;
    private String no;

    public Student(String name, String no) {
    
    
        this.name = name;
        this.no = no;
    }

    public String getName() {
    
    
        return name;
    }

    public void setName(String name) {
    
    
        this.name = name;
    }

    public String getNo() {
    
    
        return no;
    }

    public void setNo(String no) {
    
    
        this.no = no;
    }

    @Override
    public String toString() {
    
    
        return "Student{" +
                "name='" + name + '\'' +
                ", no='" + no + '\'' +
                '}';
    }
}