FastJson使用

FastJson

引入依赖

<dependency>
    <groupId>com.alibabagroupId>
    <artifactId>fastjsonartifactId>
    <version>1.2.47version>
dependency>

序列化

使用的实体类和统一结果类在文章末尾

1. 将User对象转化为json字符串

@Test
    void contextLoads() {
        User user = new User();
        String[] hobbies = {"sing","dance","rap"};
        user.setId(1L);
        user.setUsername("kunkun");
        user.setAge(22);
        user.setHobbies(hobbies);
        user.setRegisterDate(new Date());
        user.setBirthday(LocalDateTime.now());

        String toJSONString = JSON.toJSONString(user);

        System.out.println(toJSONString);
    }

最后输出结果为：

{“age”:22,“birthday”:1723649279811,“hobbies”:[“sing”,“dance”,“rap”],“registerDate”:1723649279811,“username”:“kunkun”}

2. 对null值的处理
   fastjson默认会将值为null的数据留空，如果想要对没有值的数据赋为null时可以添加一个参数

//对于对象中包含null值时
String toJSONString = JSON.toJSONString(user, SerializerFeature.WriteMapNullValue);

3. 对日期的格式化

//对实体类修改
//fastjson序列化日期格式
@JSONField(format = "yyyy-MM-dd HH:mm:ss")
private Date registerDate;

@JSONField(format = "yyyy-MM-dd HH:mm:ss")
private LocalDateTime birthday;

4. $Ref引用探测

@Test
void Test$Ref() {
    ArrayList<User> userList = new ArrayList<>();
    User user = new User();
    user.setId(1L);
    user.setUsername("zhangsan");
    user.setAge(22);
    userList.add(user);
    userList.add(user);
    userList.add(user);
    //直接打印输出结果为：[{"age":22,"id":1,"username":"zhangsan"},{"$ref":"$[0]"},{"$ref":"$[0]"}]
    //String json = JSON.toJSONString(userList);

    //禁用引用探测功能
    String json = JSON.toJSONString(userList,SerializerFeature.DisableCircularReferenceDetect);
	//会发现结果变为正常
    System.out.println(json);
}

对于SerializerFilter定制处理，等用到再学

反序列化

1. 普通反序列化

@Test
void FastJsonSerializerFilter(){
    String json = "{\"age\":22,\"birthday\":\"2024-08-14 23:36:47\",\"hobbies\":[\"sing\",\"dance\",\"rap\"],\"id\":null,\"registerDate\":\"2024-08-14 23:36:47\",\"username\":\"kunkun\"}";

    //反序列化为user对象
    User user = JSON.parseObject(json, User.class);

    //User(id=null, username=kunkun, age=22, hobbies=[sing, dance, rap], registerDate=Wed Aug 14 23:36:47 CST 2024, birthday=2024-08-14T23:36:47)
    System.out.println(user);
}

2. 遇到泛型，的解决方式
   例如统一给调用端返回Result类，并且Result中采用了泛型data

String resultJson = "{\"code\":200,\"data\":{\"age\":22,\"birthday\":\"2024-08-14 23:56:34\",\"hobbies\":[\"sing\",\"dance\",\"rap\"],\"id\":null,\"registerDate\":\"2024-08-14 23:56:34\",\"username\":\"kunkun\"},\"msg\":\"null\"}\n";

Result result = JSON.parseObject(resultJson, Result.class);
//再进行反序列化时，默认只能返回Object类型，需要进行强制类型转换
Object data = result.getData();

//可以使用TypeReference
Result<User> o = JSON.parseObject(resultJson, new TypeReference<Result<User>>() {
});
User data1 = o.getData();

通用配置

写上在序列化或反序列化时都会生效

//指定属性名和json字符串key的对应关系
@JSONField( name = "address")
private String addr;

//不参与序列化，与反序列化
@JSONField( serialize = fales , deserialize = false)
private String password;

使用到的类

import com.alibaba.fastjson.annotation.JSONField;
import lombok.Data;

import java.time.LocalDateTime;
import java.util.Date;

@Data
public class User {

    private Long id;
    private String username;
    private int age;
    private String[] hobbies;
    //fastjson序列化日期格式
    @JSONField(format = "yyyy-MM-dd HH:mm:ss")
    private Date registerDate;

    @JSONField(format = "yyyy-MM-dd HH:mm:ss")
    private LocalDateTime birthday;

}

package com.sst.result;

import lombok.Data;

@Data
public class Result<T> {

    private int code;
    private String msg;
    private T data;

    public Result(int code, String msg, T t) {
        this.code = code;
        this.msg = msg;
        this.data = t;
    }
}