Real Collection Deserializer to parse arrays with GSON

CollectionDeserializer.java

import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;

import com.google.gson.Gson;
import com.google.gson.JsonArray;
import com.google.gson.JsonDeserializationContext;
import com.google.gson.JsonDeserializer;
import com.google.gson.JsonElement;
import com.google.gson.JsonParseException;

public class CollectionDeserializer implements JsonDeserializer<Collection<?>> {

	@Override
	public Collection<?> deserialize(JsonElement json, Type typeOfT,
			JsonDeserializationContext context) throws JsonParseException {
		Type realType = ((ParameterizedType)typeOfT).getActualTypeArguments()[0];
		
		return parseAsArrayList(json, realType);
	}

	/**
	 * @param serializedData
	 * @param type
	 * @return
	 */
    @SuppressWarnings("unchecked")
	public <T> ArrayList<T> parseAsArrayList(JsonElement json, T type) {
		ArrayList<T> newArray = new ArrayList<T>();
		Gson gson = new Gson();

		JsonArray array= json.getAsJsonArray();
		Iterator<JsonElement> iterator = array.iterator();

		while(iterator.hasNext()){
		    JsonElement json2 = (JsonElement)iterator.next();
			T object = (T) gson.fromJson(json2, (Class<?>)type);
		    newArray.add(object);
		}

		return newArray;
	}
	
}

JSONParsingTest.java

public class JSONParsingTest {
	
	List<World> worlds;
	
	@Test
	public void grantThatDeserializerWorksAndParseObjectArrays(){

		String worldAsString = "{\"worlds\": [" +
			"{\"name\":\"name1\",\"id\":1}," +
			"{\"name\":\"name2\",\"id\":2}," +
			"{\"name\":\"name3\",\"id\":3}" +
		"]}";

		GsonBuilder builder = new GsonBuilder();
		builder.registerTypeAdapter(Collection.class, new CollectionDeserializer());
		Gson gson = builder.create();
		Object decoded = gson.fromJson((String)worldAsString, JSONParsingTest.class);
		
		assertNotNull(decoded);
		assertTrue(JSONParsingTest.class.isInstance(decoded));
		
		JSONParsingTest decodedObject = (JSONParsingTest)decoded;
		assertEquals(3, decodedObject.worlds.size());
		assertEquals((Long)2L, decodedObject.worlds.get(1).getId());
	}
}

World.java

public class World {
	private String name;
	private Long id;

	public void setName(String name) {
		this.name = name;
	}

	public String getName() {
		return name;
	}

	public Long getId() {
		return id;
	}

	public void setId(Long id) {
		this.id = id;
	}
	
}

Nice solution, I used it but I got error on: CollectionDeserializer.java
...
@OverRide
public Collection<?> deserialize(JsonElement json, Type typeOfT,
...

error:
The method deserialize(JsonElement, Type, JsonDeserializationContext) of type CollectionDeserializer must override a superclass method

Any idea?

Thanks in advance

Hi @amrafu
Sorry by the late, I missed up your answer notification.

Please, which version of GSon are you using?
I will try to simulate your problem to help you! ;)

Works great! Thanks! :-)

Thanks! Exactly what I'm looking for!