Check type of Json property's value on converting to Java class

Question

Let's say I have the following Json data, here I have the id of type integer, and in Java class the type of id is String.

{
  "id": 1,
  "name": "user1"
}

@lombok.Data
@AllArgsConstructor
@NoArgsConstructor
class Data {
    String id;
    String name;
}

I want to convert the Json to the that class while strictly checking if the Json property's value is of same type as the class field.

String json = "{\"id\":1,\"name\":\"user1\"}";
ObjectMapper objectMapper = new ObjectMapper(new JsonFactory());

Data data = objectMapper.readValue(json, Data.class);
System.out.println(data);

Data(id=1, name=user1)

I want that here the conversion shouldn't happen but it gets converted.

Skod · Accepted Answer · 2023-11-13 18:35:56Z

0

One way I guess is to use a custom deserializer and do a simple type check:

public class CustomDeserializer extends StdDeserializer<String> {

  protected CustomDeserializer() {
    this(null);
  }

  protected CustomDeserializer(Class<?> vc) {
    super(vc);
  }

  @Override
  public String deserialize(JsonParser p, DeserializationContext ctxt) throws IOException, JacksonException {
    if (p.currentToken() != JsonToken.VALUE_STRING) {
      throw new InvalidFormatException(p, "Expected String type", p.getValueAsString(), String.class);
    }
    return p.getValueAsString();
  }
}

And then use that deserializer in the fields you'd like to check:

public class Data {
  @JsonDeserialize(using = CustomDeserializer.class)
  String id;
}

answered Nov 13, 2023 at 18:35

Skod

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