fastJson的JSONField注解-工具盒子

真正的快乐是内在的，它只有在人类的心灵里才能发现。------布雷默

相信关于FastJson大伙都不陌生

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

这里的性别枚举

|---------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------| | 1 2 3 4 5 6 7 8 9 10 11 | hljs java @Getter @AllArgsConstructor public enum GenderEnum { FEMALE("女", 0), MALE("男", 1); private final String name; private final Integer code; } |

写一个main函数

|------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | 1 2 3 4 5 6 7 8 9 10 | hljs java 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); } |

先运行一下

然后开始一一介绍@JSONField的属性

第一个ordinal可以指定序列化后的json字符串属性顺序

例如我们稍微配置一下

|------------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | hljs java @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; } |

然后再次运行可以看到我们序列化后的JSON串属性顺序按照升序排序了

接下来是name

它可以指定我们序列化/反序列化属性的名称

我们在name上加一个

可以看到之前的name序列化后变成了studentName

下一个是format

对于日期格式，我们可以使用它去指定日期格式

例如

|---------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 | hljs java @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; } |

序列化后结果就是这样

然后是serialize：默认为true，如果为false，序列化时会忽略该属性

然后是deserialize：默认为true，如果为false，反序列化时会忽略该属性

然后是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

parseFeatures则是可以指定一些转换选项，值为com.alibaba.fastjson.parser.Feature

这两个的值都可以是多个

下面是label，这个跳过

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

然后是serializeUsing

指定序列化时使用哪个序列化器

我们自定义一个

|---------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | 1 2 3 4 5 6 7 8 9 10 11 12 13 | hljs java /** * 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); } } |

然后执行

使用deserializeUsing指定反序列化器一样的

|---------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | 1 2 3 4 5 6 7 8 9 10 11 12 13 | hljs java 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; } } |

然后是alternateNames

可以取别名，例如json字符串中，可能叫studentName，也可能叫myName

他们都要反序列化后放入name

我们就可以使用它