FastJson使用

FastJson

引入依赖

1. <dependency>
2.     <groupId>com.alibaba</groupId>
3.     <artifactId>fastjson</artifactId>
4.     <version>1.2.47</version>
5. </dependency>

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序列化

使用的实体类和同一结果类在文章末了

• 将User对象转化为json字符串
  

1. @Test
2.     void contextLoads() {
3.         User user = new User();
4.         String[] hobbies = {"sing","dance","rap"};
5.         user.setId(1L);
6.         user.setUsername("kunkun");
7.         user.setAge(22);
8.         user.setHobbies(hobbies);
9.         user.setRegisterDate(new Date());
10.         user.setBirthday(LocalDateTime.now());
12.         String toJSONString = JSON.toJSONString(user);
14.         System.out.println(toJSONString);
15.     }

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末了输出结果为：
{“age”:22,“birthday”:1723649279811,“hobbies”:[“sing”,“dance”,“rap”],“registerDate”:1723649279811,“username”:“kunkun”}

• 对null值的处置惩罚
  fastjson默认会将值为null的数据留空，假如想要对没有值的数据赋为null时可以添加一个参数
  

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

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• 对日期的格式化
  

1. //对实体类修改
2. //fastjson序列化日期格式
3. @JSONField(format = "yyyy-MM-dd HH:mm:ss")
4. private Date registerDate;
6. @JSONField(format = "yyyy-MM-dd HH:mm:ss")
7. private LocalDateTime birthday;

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• $Ref引用探测
  

1. @Test
2. void Test$Ref() {
3.     ArrayList<User> userList = new ArrayList<>();
4.     User user = new User();
5.     user.setId(1L);
6.     user.setUsername("zhangsan");
7.     user.setAge(22);
8.     userList.add(user);
9.     userList.add(user);
10.     userList.add(user);
11.     //直接打印输出结果为：[{"age":22,"id":1,"username":"zhangsan"},{"$ref":"$[0]"},{"$ref":"$[0]"}]
12.     //String json = JSON.toJSONString(userList);
14.     //禁用引用探测功能
15.     String json = JSON.toJSONString(userList,SerializerFeature.DisableCircularReferenceDetect);
16.         //会发现结果变为正常
17.     System.out.println(json);
18. }

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对于SerializerFilter定制处置惩罚，等用到再学
反序列化

• 寻常反序列化
  

1. @Test
2. void FastJsonSerializerFilter(){
3.     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"}";
5.     //反序列化为user对象
6.     User user = JSON.parseObject(json, User.class);
8.     //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)
9.     System.out.println(user);
10. }

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• 碰到泛型，的办理方式
  例如同一给调用端返回Result类，而且Result中接纳了泛型data
  

1. 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";
3. Result result = JSON.parseObject(resultJson, Result.class);
4. //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
5. Object data = result.getData();
7. //可以使用TypeReference
8. Result<User> o = JSON.parseObject(resultJson, new TypeReference<Result<User>>() {
9. });
10. User data1 = o.getData();

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通用设置

写上在序列化或反序列化时都访问效

1. //指定属性名和json字符串key的对应关系
2. @JSONField( name = "address")
3. private String addr;
5. //不参与序列化，与反序列化
6. @JSONField( serialize = fales , deserialize = false)
7. private String password;

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使用到的类

1. import com.alibaba.fastjson.annotation.JSONField;
2. import lombok.Data;
4. import java.time.LocalDateTime;
5. import java.util.Date;
7. @Data
8. public class User {
10.     private Long id;
11.     private String username;
12.     private int age;
13.     private String[] hobbies;
14.     //fastjson序列化日期格式
15.     @JSONField(format = "yyyy-MM-dd HH:mm:ss")
16.     private Date registerDate;
18.     @JSONField(format = "yyyy-MM-dd HH:mm:ss")
19.     private LocalDateTime birthday;
21. }

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1. package com.sst.result;
3. import lombok.Data;
5. @Data
6. public class Result<T> {
8.     private int code;
9.     private String msg;
10.     private T data;
12.     public Result(int code, String msg, T t) {
13.         this.code = code;
14.         this.msg = msg;
15.         this.data = t;
16.     }
17. }

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