Jackson json to map and camelcase key name

Question

I want to convert json via jackson library to a map containing camelCase key...say...

from

{
    \"SomeKey\": \"SomeValue\",
    \"Anoth         


        

Answer 1

You always can iterate over the keys of the map and update them. However, if you are only interested in producing a JSON with camel case keys, you could consider the approach described below.

You could have a custom key serializer. It will be used when serializing a Map instance to JSON:

public class CamelCaseKeySerializer extends JsonSerializer {

    @Override
    public void serialize(String value, JsonGenerator gen, SerializerProvider serializers)
                throws IOException, JsonProcessingException {

        String key = Character.toLowerCase(value.charAt(0)) + value.substring(1);
        gen.writeFieldName(key);
    }
}

Then do as following:

String json = "{\"SomeKey\":\"SomeValue\",\"AnotherKey\":\"another value\",\"InnerJson\":"
            + "{\"TheKey\":\"TheValue\"}}";

SimpleModule simpleModule = new SimpleModule();
simpleModule.addKeySerializer(String.class, new CamelCaseKeySerializer());

ObjectMapper mapper = new ObjectMapper();
mapper.registerModule(simpleModule);

Map map = mapper.readValue(json, 
                                          new TypeReference>() {});

String camelCaseJson = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(map);

The output will be:

{
  "someKey" : "SomeValue",
  "anotherKey" : "another value",
  "innerJson" : {
    "theKey" : "TheValue"
  }
}

With this approach, the keys of the Map won't be in camel case. But it will give you the desired output.