/*******************************************************************************
* Copyright (c) 2007, 2015 Willink Transformations and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* E.D.Willink - initial API and implementation
*******************************************************************************/
package org.eclipse.ocl.examples.modelregistry.environment;
import org.eclipse.ocl.pivot.utilities.ClassUtil;
/**
* ClassDelegate captures a class name mentioned in an extension, but defers loading that
* class until it is actually needed.
*/
public abstract class ClassDelegate<T> {
protected final String className;
protected final Class<T> clazz;
private T instance = null;
private boolean loaded = false;
public ClassDelegate(String className, Class<T> clazz) {
this.className = className;
this.clazz = clazz;
}
public ClassDelegate(T instance) {
this.className = instance.getClass().getName();
this.clazz = ClassUtil.getClass(instance);
this.instance = instance;
this.loaded = true;
}
@SuppressWarnings("unchecked")
public T load() {
if ((instance == null) && !loaded) {
loaded = true;
try {
Class<?> loadedClass = loadClass(className);
if (!clazz.isAssignableFrom(loadedClass))
throw new ClassCastException("model_content extension requires " + loadedClass.getName() + " to be assignable to " + clazz.getName());
instance = (T) loadedClass.newInstance();
} catch (Exception e) {
ModelRegistryEnvironment.logError("Failed to load model content '" + className + "'", e);
}
}
return instance;
}
protected abstract Class<?> loadClass(String className) throws ClassNotFoundException;
@Override public String toString() {
return className;
}
}