EmptyStringToNullDeserializer.java

import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonDeserializer;
import com.fasterxml.jackson.databind.module.SimpleModule;
import java.io.IOException;

public class EmptyStringToNullDeserializer extends JsonDeserializer<String> {
    @Override
    public String deserialize(JsonParser jsonParser, DeserializationContext context) throws IOException {
        String value = jsonParser.getValueAsString();
        if (value != null && value.isEmpty()) {
            return null;
        }
        return value;
    }

    public static SimpleModule module() {
        SimpleModule module = new SimpleModule();
        module.addDeserializer(String.class, new EmptyStringToNullDeserializer());
        return module;
    }
}