java - Jackson databind enum case insensitive

Question

How can I deserialize JSON string that contains enum values that are case insensitive? (using Jackson Databind)

The JSON string:

[{"url": "foo", "type": "json"}]

and my Java POJO:

public static class Endpoint {

    public enum DataType {
        JSON, HTML
    }

    public String url;
    public DataType type;

    public Endpoint() {

    }

}

in this case,deserializing the JSON with "type":"json" would fail where as "type":"JSON" would work. But I want "json" to work as well for naming convention reasons.

Serializing the POJO also results in upper case "type":"JSON"

I thought of using @JsonCreator and @JsonGetter:

    @JsonCreator
    private Endpoint(@JsonProperty("name") String url, @JsonProperty("type") String type) {
        this.url = url;
        this.type = DataType.valueOf(type.toUpperCase());
    }

    //....
    @JsonGetter
    private String getType() {
        return type.name().toLowerCase();
    }

And it worked. But I was wondering whether there's a better solutuon because this looks like a hack to me.

I can also write a custom deserializer but I got many different POJOs that use enums and it would be hard to maintain.

Can anyone suggest a better way to serialize and deserialize enums with proper naming convention?

I don't want my enums in java to be lowercase!

Here is some test code that I used:

    String data = "[{"url":"foo", "type":"json"}]";
    Endpoint[] arr = new ObjectMapper().readValue(data, Endpoint[].class);
        System.out.println("POJO[]->" + Arrays.toString(arr));
        System.out.println("JSON ->" + new ObjectMapper().writeValueAsString(arr));

Answer 1

Jackson 2.9

This is now very simple, using jackson-databind 2.9.0 and above

ObjectMapper objectMapper = new ObjectMapper();
objectMapper.enable(MapperFeature.ACCEPT_CASE_INSENSITIVE_ENUMS);

// objectMapper now deserializes enums in a case-insensitive manner

---

Full example with tests

import com.fasterxml.jackson.databind.MapperFeature;
import com.fasterxml.jackson.databind.ObjectMapper;

public class Main {

  private enum TestEnum { ONE }
  private static class TestObject { public TestEnum testEnum; }

  public static void main (String[] args) {
    ObjectMapper objectMapper = new ObjectMapper();
    objectMapper.enable(MapperFeature.ACCEPT_CASE_INSENSITIVE_ENUMS);

    try {
      TestObject uppercase = 
        objectMapper.readValue("{ "testEnum": "ONE" }", TestObject.class);
      TestObject lowercase = 
        objectMapper.readValue("{ "testEnum": "one" }", TestObject.class);
      TestObject mixedcase = 
        objectMapper.readValue("{ "testEnum": "oNe" }", TestObject.class);

      if (uppercase.testEnum != TestEnum.ONE) throw new Exception("cannot deserialize uppercase value");
      if (lowercase.testEnum != TestEnum.ONE) throw new Exception("cannot deserialize lowercase value");
      if (mixedcase.testEnum != TestEnum.ONE) throw new Exception("cannot deserialize mixedcase value");

      System.out.println("Success: all deserializations worked");
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
}