injectorholder.java

Wicket一个开发Java Web应用程序框架。它使得开发web应用程序变得容易而轻松。 Wicket利用一个POJO data beans组件使得它可以与任何持久层技术相结合。

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.wicket.injection.web;

import org.apache.wicket.injection.ConfigurableInjector;

/**
 * Holds a reference to the injector that will be used to automatically initialize components that
 * are used. Usually the application class should set the injector in the holder when it
 * initializes.
 * <p>
 * This class can be used for unit-testing to switch the standard injector with an injector that
 * will lookup dependencies from a mock application context.
 * <p>
 * 
 * <pre>
 * class MockSpringInjector extends SpringInjector
 * {
 * 	protected ISpringContextLocator getContextLocator()
 * 	{
 * 		return new MockContextLocator();
 * 	}
 * }
 * 
 * InjectorHolder.setInjector(new MockSpringInjector());
 * 
 * //from this point on InjectableWebPage and InjectablePanel
 * //will be injected using the MockSpringInjector 
 * </pre>
 * 
 * @author Igor Vaynberg (ivaynberg)
 * 
 * TODO shouldn't we move this class to org.apache.wicket.injection ?
 */
public class InjectorHolder
{
	private static ConfigurableInjector injector = null;

	/**
	 * Gets an injector
	 * 
	 * NOTICE this method is not thread safe if setInjector() is used
	 * 
	 * @return injector
	 */
	public static ConfigurableInjector getInjector()
	{
		if (injector == null)
		{
			throw new IllegalStateException("InjectorHolder has not been assigned an injector. "
					+ "Use InjectorHolder.setInjector() to assign an injector. "
					+ "In most cases this should be done once inside "
					+ "SpringWebApplication subclass's init() method.");
		}
		return injector;
	}

	/**
	 * Sets an injector
	 * 
	 * NOTICE this method is not thread safe.
	 * 
	 * @param newInjector
	 *            new injector
	 */
	public static void setInjector(ConfigurableInjector newInjector)
	{
		injector = newInjector;
	}

}