javajsonserializationjacksonjsonserializer

Jackson deserializing into Map with an Enum Key, POJO Value


I am trying to deserialize JSON into a Java POJO using Jackson. Without giving away confidential information, here is an example stack trace when ObjectMapper's deserialization fails:

org.codehaus.jackson.map.JsonMappingException: Can not construct Map key of type com.example.MyEnum from String "coins": not a valid representation: Can not construct Map key of type com.example.MyEnum from String "coins": not one of values for Enum class

My JSON looks like this:

"foo": {
    "coins": null,
    ...
}

And the class I want to deserialize into has this field:

private Map<MyEnum, MyPojo> foo;

And my enum type looks like this:

public enum MyEnum {
    COINS("coins"),
    ...
}

I do realize that I am trying to deserialize a null value. But I believe this should still work: the result of the deserialization should be equivalent to having a Map with foo.put(MyEnum.COINS, null), which is indeed a valid Java instruction. Help is much appreciated, thanks in advance.


Solution

  • In addition to one good solution presented (factory method), there are 2 other ways: