JsonHandlers to create document model consisting of JSONArrays and JSONObjects using a JsonPushParser

AbstractHandler.java

import java.util.ArrayDeque;
import java.util.Deque;

import org.json.JSONArray;
import org.json.JSONObject;

import net.markenwerk.utils.json.parser.JsonHandler;

/**
 * JsonHandler that creates a document model consisting of JSONArrays and
 * JSONObjects
 */
public abstract class AbstractHandler<Result> implements JsonHandler<Result> {

	/**
	 * Simplified handler interface, that is used to fill JSONArrays and
	 * JSONObjects
	 */
	private static interface Handler<Result> {

		public void onName(String name);

		public void onNull();

		public void onValue(Object value);

		public Result getResult();

	}

	// stack that contains handlers for the commenced JSONArrays and JSONObjects
	private Deque<Handler<?>> stack = new ArrayDeque<Handler<?>>();

	// handler for the current JSONArray or JSONobject
	private Handler<?> handler;

	@Override
	public void onDocumentBegin() {

		// create a root handler, that holds the root JSONArray or JSONObject
		handler = new Handler<Object>() {

			private Object result;

			@Override
			public void onName(String name) {
			}

			@Override
			public void onNull() {
			}

			@Override
			public void onValue(Object value) {
				result = value;
			}

			@Override
			public Object getResult() {
				return result;
			}
		};
	}

	@Override
	public void onDocumentEnd() {
	}

	@Override
	public void onArrayBegin() {

		// add a new JSONArray to the last JSONArray of JSONObject
		final JSONArray array = new JSONArray();
		handler.onValue(array);

		// create a new handler that adds the following values to array
		stack.push(handler);
		handler = new Handler<JSONArray>() {

			@Override
			public void onName(String name) {
			}

			@Override
			public void onNull() {
				array.put((Object) null);
			}

			@Override
			public void onValue(Object value) {
				array.put(value);
			}

			@Override
			public JSONArray getResult() {
				return array;
			}

		};

	}

	@Override
	public void onArrayEnd() {
		// add the following values to the previous JSONArray or JSONObject
		handler = stack.pop();
	}

	@Override
	public void onObjectBegin() {

		// add a new JSONObject to the last JSONArray of JSONObject
		final JSONObject object = new JSONObject();
		handler.onValue(object);

		// create a new handler that adds the following values to object
		stack.push(handler);
		handler = new Handler<JSONObject>() {

			private String name;

			@Override
			public void onName(String name) {
				this.name = name;
			}

			@Override
			public void onNull() {
				object.put(name, JSONObject.NULL);
			}

			@Override
			public void onValue(Object value) {
				object.put(name, value);
			}

			@Override
			public JSONObject getResult() {
				return object;
			}

		};
	}

	@Override
	public void onName(String name) {
		handler.onName(name);
	}

	@Override
	public void onEndObject() {
		// add the following values to the previous JSONArray or JSONObject
		handler = stack.pop();
	}

	@Override
	public void onNull() {
		handler.onNull();
	}

	@Override
	public void onBoolean(boolean value) {
		handler.onValue(value);
	}

	@Override
	public void onLong(long value) {
		handler.onValue(value);
	}

	@Override
	public void onDouble(double value) {
		handler.onValue(value);
	}

	@Override
	public void onString(String value) {
		handler.onValue(value);
	}

	/**
	 * Returns the root object and ensures that it is a JSONObject
	 */
	protected JSONObject getRootObject() {
		try {
			return (JSONObject) handler.getResult();
		} catch (ClassCastException e) {
			throw new IllegalStateException("JSON document contains a JSON array, not a JSON object");
		}
	}

	/**
	 * Returns the root object and ensures that it is a JSONArray
	 */
	protected JSONArray getRootArray() {
		try {
			return (JSONArray) handler.getResult();
		} catch (ClassCastException e) {
			throw new IllegalStateException("JSON document contains a JSON object, not a JSON array");
		}	}

}

ArrayHandler.java

import org.json.JSONArray;

public class ArrayHandler extends AbstractHandler<JSONArray> {

	@Override
	public JSONArray getResult() {
		return getRootArray();
	}

}

ObjectHandler.java

import org.json.JSONObject;

public class ObjectHandler extends AbstractHandler<JSONObject> {

	@Override
	public JSONObject getResult() {
		return getRootObject();
	}

}