@JsonEnumDefaultValue 标記枚舉的預設值

@JsonEnumDefaultValue

用于定義在嘗試反序列化未知枚舉值使用的預設值。隻能應用于字段上，且隻有在

READ_UNKNOWN_ENUM_VALUES_USING_DEFAULT_VALUE

反序列化功能啟用其才有效。

Example

Example Enum

public enum EmployeeType {
    FullTime,
    PartTime,
    @JsonEnumDefaultValue
    Contractor;
}
           

反序列化

有效的枚舉值

public class ExampleMain {
    public static void main(String[] args) throws IOException {
        String jsonString = "\"FullTime\"";
        System.out.println("-- Json string to deserialize --");
        System.out.println(jsonString);

        ObjectMapper om = new ObjectMapper();
        om.enable(DeserializationFeature.READ_UNKNOWN_ENUM_VALUES_USING_DEFAULT_VALUE);
        
        EmployeeType type = om.readValue(jsonString, EmployeeType.class);
        System.out.println("-- after deserialization --");
        System.out.println(type);
    }
}
           

-- Json string to deserialize --
"FullTime"
-- after deserialization --
FullTime
           

無效的枚舉值

public class ExampleMain2 {
    public static void main(String[] args) throws IOException {
        String jsonString = "\"remote\"";
        System.out.println("-- Json string to deserialize --");
        System.out.println(jsonString);

        ObjectMapper om = new ObjectMapper();
        om.enable(DeserializationFeature.READ_UNKNOWN_ENUM_VALUES_USING_DEFAULT_VALUE);

        EmployeeType type = om.readValue(jsonString, EmployeeType.class);
        System.out.println("-- after deserialization --");
        System.out.println(type);
    }
}
           

-- Json string to deserialize --
"remote"
-- after deserialization --
Contractor
           

不使用 @JsonEnumDefaultValue

-- Json string to deserialize --
"remote"
Exception in thread "main" com.fasterxml.jackson.databind.exc.InvalidFormatException: Cannot deserialize value of type `org.example.c32.EmployeeType` from String "remote": not one of the values accepted for Enum class: [PartTime, FullTime, Contractor]
 at [Source: (String)""remote""; line: 1, column: 1]
	at com.fasterxml.jackson.databind.exc.InvalidFormatException.from(InvalidFormatException.java:67)
	at com.fasterxml.jackson.databind.DeserializationContext.weirdStringException(DeserializationContext.java:1851)
	at com.fasterxml.jackson.databind.DeserializationContext.handleWeirdStringValue(DeserializationContext.java:1079)
	at com.fasterxml.jackson.databind.deser.std.EnumDeserializer._deserializeAltString(EnumDeserializer.java:327)
	at com.fasterxml.jackson.databind.deser.std.EnumDeserializer._fromString(EnumDeserializer.java:214)
	at com.fasterxml.jackson.databind.deser.std.EnumDeserializer.deserialize(EnumDeserializer.java:188)
	at com.fasterxml.jackson.databind.deser.DefaultDeserializationContext.readRootValue(DefaultDeserializationContext.java:322)
	at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4593)
	at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3548)
	at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3516)
	at org.example.c32.ExampleMain2.main(ExampleMain2.java:21)

Process finished with exit code 1

           

原文連結

Jackson JSON - Using @JsonEnumDefaultValue to mark enum element as default