How to deserialize a blank JSON string value to null for java.lang.String?

Question

I am trying a simple JSON to de-serialize in to java object. I am however, getting empty String values for java.lang.String property values. In rest of

Answer 1

You might first like to see if there has been any progress on the Github issue requesting this exact feature.

For those using Spring Boot: The answer from jgesser was the most helpful to me, but I spent a while trying to work out the best way to configure it in Spring Boot.

Actually, the documentation says:

Any beans of type com.fasterxml.jackson.databind.Module are automatically registered with the auto-configured Jackson2ObjectMapperBuilder and are applied to any ObjectMapper instances that it creates.

So here's jgesser's answer expanded into something you can copy-paste into a new class in a Spring Boot application

@Configuration
public class EmptyStringAsNullJacksonConfiguration {

  @Bean
  SimpleModule emptyStringAsNullModule() {
    SimpleModule module = new SimpleModule();

    module.addDeserializer(
        String.class,
        new StdDeserializer(String.class) {

          @Override
          public String deserialize(JsonParser parser, DeserializationContext context)
              throws IOException {
            String result = StringDeserializer.instance.deserialize(parser, context);
            if (StringUtils.isEmpty(result)) {
              return null;
            }
            return result;
          }
        });

    return module;
  }
}