Jackson 使用 @JsonRootName 反序列化具有额外属性的 JSON

Question

I want to deserialize an object which is annotated with @JsonRootName . However the JSON in which the object is transported contains another extra property. As a result Jackson is complaining with:

com.fasterxml.jackson.databind.exc.MismatchedInputException: Unexpected token (FIELD_NAME), expected END_OBJECT: Current token not END_OBJECT (to match wrapper object with root name 'account'), but FIELD_NAME at [Source: (ByteArrayInputStream); line: 1, column: 26] com.fasterxml.jackson.databind.exc.MismatchedInputException: Unexpected token (FIELD_NAME), expected END_OBJECT: Current token not END_OBJECT (to match wrapper object with root name 'account'), but FIELD_NAME at [Source: (ByteArrayInputStream); line: 1, column: 26] .

Apparently deserialization of @JsonRootName annotated objects works ONLY if that object is the sole property in JSON file - since it's not expecting the "lastTransactionID" to be there.

Here's my Account class:

@JsonRootName("account")
public class Account {
    private String id;
}

This is the JSON I need to deserialise:

{
  "account": {
    "id": "1234"
  },
  "lastTransactionID": "1"
}

Since I'm using spring I have this setup also spring.jackson.deserialization.unwrap_root_value=true .

Is there any way to solve this without:

• having to write a custom deserializer?

OR

• intercepting the response and stripping it of the extra property before deserialization takes place?

Answer 1

It looks like simplest way to solve this issue is create wrapper for Account class and deserialise json as usual with disabled DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES feature.

public static class Wrapper {
    public Account account;
}

In this case other fields will be ignored.

It's not a nice solution, I know, but it solve a problem.

Answer 2

We can use ObjectMapper to Map json to java Objects.

public Account jsonToObject(Map<String, Object> map){
    ObjectMapper objectMapper = new ObjectMapper();
    Account account = objectMapper.convertvalue(map.get("account"),Account.class);
    return account;
}

Answer 3

You can use JsonIgnoreProperties(ignoreUnknown=true) annotation on your Account class. Please refer below link for more details.
https://www.thetechnojournals.com/2019/10/entity-object-conversion-to-dto-object.html