92 lines
2.6 KiB
Java
92 lines
2.6 KiB
Java
|
/*
|
||
|
|
* Copyright (C) 2011 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 org.mcteam.factions.gson;
|
||
|
|
|
||
|
|
|
||
|
|
import java.lang.reflect.Constructor;
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Use the default constructor on the class to instantiate an object.
|
||
|
|
*
|
||
|
|
* @author Joel Leitch
|
||
|
|
*/
|
||
|
|
final class DefaultConstructorAllocator {
|
||
|
|
private static final Constructor<Null> NULL_CONSTRUCTOR = createNullConstructor();
|
||
|
|
|
||
|
|
private final Cache<Class<?>, Constructor<?>> constructorCache;
|
||
|
|
|
||
|
|
public DefaultConstructorAllocator() {
|
||
|
|
this(200);
|
||
|
|
}
|
||
|
|
|
||
|
|
public DefaultConstructorAllocator(int cacheSize) {
|
||
|
|
constructorCache = new LruCache<Class<?>, Constructor<?>>(cacheSize);
|
||
|
|
}
|
||
|
|
|
||
|
|
// for testing purpose
|
||
|
|
final boolean isInCache(Class<?> cacheKey) {
|
||
|
|
return constructorCache.getElement(cacheKey) != null;
|
||
|
|
}
|
||
|
|
|
||
|
|
private static final Constructor<Null> createNullConstructor() {
|
||
|
|
try {
|
||
|
|
return getNoArgsConstructor(Null.class);
|
||
|
|
} catch (Exception e) {
|
||
|
|
return null;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
public <T> T newInstance(Class<T> c) throws Exception {
|
||
|
|
Constructor<T> constructor = findConstructor(c);
|
||
|
|
return (constructor != null) ? constructor.newInstance() : null;
|
||
|
|
}
|
||
|
|
|
||
|
|
@SuppressWarnings("unchecked")
|
||
|
|
private <T> Constructor<T> findConstructor(Class<T> c) {
|
||
|
|
Constructor<T> cachedElement = (Constructor<T>) constructorCache.getElement(c);
|
||
|
|
if (cachedElement != null) {
|
||
|
|
if (cachedElement == NULL_CONSTRUCTOR) {
|
||
|
|
return null;
|
||
|
|
} else {
|
||
|
|
return cachedElement;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
Constructor<T> noArgsConstructor = getNoArgsConstructor(c);
|
||
|
|
if (noArgsConstructor != null) {
|
||
|
|
constructorCache.addElement(c, noArgsConstructor);
|
||
|
|
} else {
|
||
|
|
constructorCache.addElement(c, NULL_CONSTRUCTOR);
|
||
|
|
}
|
||
|
|
return noArgsConstructor;
|
||
|
|
}
|
||
|
|
|
||
|
|
private static <T> Constructor<T> getNoArgsConstructor(Class<T> c) {
|
||
|
|
try {
|
||
|
|
Constructor<T> declaredConstructor = c.getDeclaredConstructor();
|
||
|
|
declaredConstructor.setAccessible(true);
|
||
|
|
return declaredConstructor;
|
||
|
|
} catch (Exception e) {
|
||
|
|
return null;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
// placeholder class for Null constructor
|
||
|
|
private static final class Null {
|
||
|
|
}
|
||
|
|
}
|