一、前言

今天聊聊fastjson的这个注解@JSONField

首先它可以放到方法上

例如我们pojo的getter和setter等

其次用的最多的是放到属性上

  • 例如我这里新建一个POJO
@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
private static class Student implements Serializable {
    private static final long serialVersionUID = -3289647584974663707L;
    private String name;
    private Integer age;
    private String job;
    private GenderEnum gender;
    private Date birthday;
    private String json;
}
  • 这里的性别枚举
@Getter
@AllArgsConstructor
public enum GenderEnum {

    FEMALE("女", 0),
    MALE("男", 1);

    private final String name;
    private final Integer code;

}
  • 运行测试
public static void main(String[] args) {
    Instant from = LocalDateTime.parse("2021-01-09 00:00:00", DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss", Locale.ENGLISH)).toInstant(ZoneOffset.MAX);

    Student supa = Student.builder().name("supa").age(20).gender(GenderEnum.MALE).birthday(Date.from(from)).json("{\"word\":\"xxx\"}").build();
    String serializeStr = JSON.toJSONString(supa);
    System.out.println(serializeStr);

    Student student = JSON.parseObject(serializeStr, Student.class);
    System.out.println(student);
}
  • 运行结果

1-fastjson.png

二、@JSONField的属性

1、ordinal

  • ordinal可以指定序列化后的json字符串属性顺序
@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
private static class Student implements Serializable {
    private static final long serialVersionUID = -3289647584974663707L;
    
    @JSONField(ordinal = 3)
    private String name;
    
    @JSONField(ordinal = 1)
    private Integer age;
    
    private String job;
    
    @JSONField(ordinal = 2)
    private GenderEnum gender;
    
    private Date birthday;
    
    private String json;
}
  • 运行结果

2-fastjson.png

2、name

  • 它可以指定我们序列化/反序列化属性的名称
@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
private static class Student implements Serializable {
    private static final long serialVersionUID = -3289647584974663707L;
    
    @JSONField(ordinal = 3,name = "studentName")
    private String name;
    
    @JSONField(ordinal = 1)
    private Integer age;
    
    private String job;
    
    @JSONField(ordinal = 2)
    private GenderEnum gender;
    
    private Date birthday;
    
    private String json;
}
  • 运行结果
  • 我们可以看到原本的字段名为name的，序列化之后变成了我们指定的studentName

3-fastjson.png

3、format

  • 对于日期格式，我们可以使用它去指定日期格式
Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
private static class Student implements Serializable {
    private static final long serialVersionUID = -3289647584974663707L;
    @JSONField(ordinal = 3, name = "studentName")
    private String name;
    
    @JSONField(ordinal = 1)
    private Integer age;
    
    private String job;
    
    @JSONField(ordinal = 2)
    private GenderEnum gender;
    
    @JSONField(format = "yyyy年MM月dd日E")
    private Date birthday;
    
    private String json;
}
  • 运行结果

4-fastjson.png

4、serialize

  • serialize：默认为true，如果为false，序列化时会忽略该属性
    @JSONField(ordinal = 1,serialize=false)
    private Integer age;
  • 运行结果

5-fastjson.png

5、deserialize

  • 然后是deserialize：默认为true，如果为false，反序列化时会忽略该属性
    @JSONField(format = "yyyy年MM月dd日E",deserialize = false)
    private Date birthday;
  • 运行结果

6-fastjson.png

6、serialzeFeatures

  • 它的值为com.alibaba.fastjson.serializer.SerializerFeature
  • 可以指定一些序列化的选项，例如我们值为null时序列化为空串
@JSONField(serialzeFeatures = {SerializerFeature.WriteNullStringAsEmpty})
private String job;
  • 运行结果

7-fastjson.png

7、jsonDirect

  • jsonDirect针对值为json字符串的属性，为true则序列化，为false则不序列化，默认为false
@JSONField(jsonDirect = true)
private String json;
  • 运行结果

8-fastjson.png

8、serializeUsing

  • serializeUsing 可以指定自定义的序列化器
@JSONField(ordinal = 2,serializeUsing = GenderEnumParser.class)
private GenderEnum gender;
  • 自定义序列化器
/**
 * 性别序列化
 */
public static class GenderEnumParser implements ObjectSerializer {
    @Override
    public void write(JSONSerializer serializer, Object object, Object fieldName, Type fieldType, int features) throws IOException {
        Integer genderCode = null;
        if (fieldType.getTypeName().equals(GenderEnum.class.getName())) {
            genderCode = ((GenderEnum) object).getCode();
        }
        serializer.write(genderCode);
    }
}
  • 运行结果

9-fastjson.png

9、deserializeUsing

  • 与serializeUsing相似，可以指定自定义的反序列化器
@JSONField(ordinal = 2,serializeUsing = GenderEnumParser.class, deserializeUsing = GenderEnumFormatter.class)
private GenderEnum gender;
  • 自定义反序列化器
public static class GenderEnumFormatter implements ObjectDeserializer {
    @Override
    public <T> T deserialze(DefaultJSONParser parser, Type type, Object fieldName) {
        JSONObject jsonObject = JSON.parseObject(parser.getInput());
        Integer genderCode = jsonObject.getInteger(String.valueOf(fieldName));
        return (T) Arrays.stream(GenderEnum.values()).filter(gender -> gender.getCode().equals(genderCode)).findFirst().orElse(null);
    }

    @Override
    public int getFastMatchToken() {
        return 0;
    }
}