WebletContainer.java

/*
 * Copyright 2005 John R. Fallows
 *
 * 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 net.java.dev.weblets;

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

abstract public class WebletContainer {
	static protected void setInstance(WebletContainer container) throws WebletException {
		ClassLoader loader = getLoader();
		_INSTANCES.put(loader, container);
	}

	/* we store the valid classoader on a per thread base to bypass a performance leak */
	static final int	CLASSLOADER_CONTEXT		= 0;
	static final int	CLASSLOADER_LOCAL		= 1;
	static final int	CLASSLOADER_UNDEFINED	= -1;
	static int			classloaderType			= CLASSLOADER_UNDEFINED;	/* we do not keep the classloader only the type */

	/**
	 * caching loader determination algorithm
	 * 
	 * @return a valid classloader with access to our resources
	 */
	public static ClassLoader getLoader() {
		/* once we are at a classloader we have to stay there! */
		if (classloaderType != CLASSLOADER_UNDEFINED) {
			switch (classloaderType) {
			case CLASSLOADER_LOCAL:
				return WebletContainer.class.getClassLoader();
			default:
				return Thread.currentThread().getContextClassLoader();
			}
		} else {
			ClassLoader loader = null;
			loader = Thread.currentThread().getContextClassLoader();
			URL testRes = loader.getResource("META-INF/services/" + WebletContainer.class.getName());
			classloaderType = CLASSLOADER_CONTEXT;
			if (testRes == null) { /* on some containers we do not have access to the resources over the context classloader at certain times */
				loader = WebletContainer.class.getClassLoader();
				classloaderType = CLASSLOADER_LOCAL;
			}
			return loader;
		}
	}

	static public WebletContainer getInstance() throws WebletException {
		ClassLoader loader = getLoader();
		return (WebletContainer) _INSTANCES.get(loader);
	}

	abstract public String getWebletContextPath();

	abstract public void setWebletContextPath(String contextPath);

	abstract public void service(WebletRequest request, WebletResponse response) throws IOException, WebletException;

	abstract public String getResourceUri(String webletName, String pathInfo) throws WebletException;

	/**
	 * returns the mimetype of the underlying hosting container
	 * 
	 * @param pattern
	 * @return
	 */
	public abstract String getContainerMimeType(String pattern);

	/**
	 * Method which returns the actual resource as input stream from a given weblet request
	 * 
	 * @param request
	 *            the current request
	 * @return an input stream on the resource
	 * @throws WebletException
	 */
	abstract public InputStream getResourceStream(WebletRequest request, String mimetype) throws WebletException;

	static private final Map	_INSTANCES	= Collections.synchronizedMap(new HashMap());
}