MappedObjectConstructor.java

/*
 * Copyright (C) 2008 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.smartandroid.sa.json;

import java.lang.reflect.Array;
import java.lang.reflect.Type;

import com.smartandroid.sa.json.internal.$Gson$Types;
import com.smartandroid.sa.json.internal.UnsafeAllocator;

/**
 * This class contains a mapping of all the application specific
 * {@link InstanceCreator} instances. Registering an {@link InstanceCreator}
 * with this class will override the default object creation that is defined by
 * the ObjectConstructor that this class is wrapping. Using this class with the
 * JSON framework provides the application with "pluggable" modules to customize
 * framework to suit the application's needs.
 * 
 * @author Joel Leitch
 */
final class MappedObjectConstructor implements ObjectConstructor {
	private static final UnsafeAllocator unsafeAllocator = UnsafeAllocator
			.create();
	private static final DefaultConstructorAllocator defaultConstructorAllocator = new DefaultConstructorAllocator(
			500);

	private final ParameterizedTypeHandlerMap<InstanceCreator<?>> instanceCreatorMap;

	public MappedObjectConstructor(
			ParameterizedTypeHandlerMap<InstanceCreator<?>> instanceCreators) {
		instanceCreatorMap = instanceCreators;
	}

	@SuppressWarnings("unchecked")
	public <T> T construct(Type typeOfT) {
		InstanceCreator<T> creator = (InstanceCreator<T>) instanceCreatorMap
				.getHandlerFor(typeOfT, false);
		if (creator != null) {
			return creator.createInstance(typeOfT);
		}
		return (T) constructWithAllocators(typeOfT);
	}

	public Object constructArray(Type type, int length) {
		return Array.newInstance($Gson$Types.getRawType(type), length);
	}

	@SuppressWarnings({ "unchecked", "cast" })
	private <T> T constructWithAllocators(Type typeOfT) {
		try {
			Class<T> clazz = (Class<T>) $Gson$Types.getRawType(typeOfT);
			T obj = defaultConstructorAllocator.newInstance(clazz);
			return (obj == null) ? unsafeAllocator.newInstance(clazz) : obj;
		} catch (Exception e) {
			throw new RuntimeException(
					("Unable to invoke no-args constructor for " + typeOfT
							+ ". " + "Register an InstanceCreator with Gson for this type may fix this problem."),
					e);
		}
	}

	@Override
	public String toString() {
		return instanceCreatorMap.toString();
	}
}