How to handle different data types with same attribute name with Gson?

Question

I\'m currently writing an RSS feed parser in Java utilizing Gson. I\'m converting the RSS\' XML into JSON, and then subsequently using Gson to deserialize the JSON into Java

Answer 1

My answer is to make use of a class hierarchy.

abstract class Guid {
    private boolean isPermalink;
    private String content;
    // getters and setters omitted
}

class GuidObject extends Guid {} 
class GuidString extends Guid {}

class RssFeedItem {
    // super class to receive instances of sub classes
    private Guid guid; 
}

And register a deserializer for Guid:

GsonBuilder builder = new GsonBuilder();
builder.registerTypeAdapter(Guid.class, new JsonDeserializer() {
        @Override
        public Guid deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
            // Dispatch based on the type of json
            if (json.isJsonObject()) {
                // If it's an object, it's essential we deserialize
                // into a sub class, otherwise we'll have an infinite loop
                return context.deserialize(json, GuidObject.class);
            } else if (json.isJsonPrimitive()) {
                // Primitive is easy, just set the most
                // meaningful field. We can also use GuidObject here
                // But better to keep it clear.
                Guid guid = new GuidString();
                guid.setContent(json.getAsString());
                return guid;
            }
            // Cannot parse, throw exception
            throw new JsonParseException("Expected Json Object or Primitive, was " + json + ".");
        }
    });

This way you can potentially handle much more complex JSON objects, and dispatch based on whatever criteria you like.