nextapp.echo.app.util.PeerFactory Maven / Gradle / Ivy
/*
* This file is part of the Echo Web Application Framework (hereinafter "Echo").
* Copyright (C) 2002-2009 NextApp, Inc.
*
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (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.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* Alternatively, the contents of this file may be used under the terms of
* either the GNU General Public License Version 2 or later (the "GPL"), or
* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*/
package nextapp.echo.app.util;
import java.io.IOException;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import nextapp.echo.app.util.PropertiesDiscovery;
/**
* A mechanism for retrieving instances of singleton peer objects which are
* defined to each support a specific Class.
* A properties file is used to associate peer classes with their supported
* classes. The properties file should contain the fully qualified class
* names of the supported objects as its keys. The values of the properties
* file should contain the fully qualified class names of the peer objects.
* A single instance of each peer class will be used to support ALL instances
* of the supported class.
*/
public class PeerFactory {
private final Map objectClassNameToPeerMap = new HashMap();
/**
* Creates a new PeerFactory.
*
* @param resourceName the name of the resource properties file from which
* the peer bindings may be retrieved (this file will be retrieved
* using the PropertiesDiscovery system, so multiple
* instances of the file within the CLASSPATH will be
* automatically discovered.
* @param classLoader the ClassLoader to use for retrieving the
* resource file and for instantiating the peer singleton instances
*/
public PeerFactory(String resourceName, ClassLoader classLoader) {
try {
Map peerNameMap = PropertiesDiscovery.loadProperties(resourceName, classLoader);
Iterator it = peerNameMap.keySet().iterator();
while (it.hasNext()) {
String objectClassName = ((String) it.next()).trim();
String peerClassName = ((String) peerNameMap.get(objectClassName)).trim();
Class peerClass = classLoader.loadClass(peerClassName);
Object peer = peerClass.newInstance();
objectClassNameToPeerMap.put(objectClassName, peer);
}
} catch (ClassNotFoundException ex) {
throw new RuntimeException("Unable to load synchronize peer bindings.", ex);
} catch (IOException ex) {
throw new RuntimeException("Unable to load synchronize peer bindings.", ex);
} catch (InstantiationException ex) {
throw new RuntimeException("Unable to load synchronize peer bindings.", ex);
} catch (IllegalAccessException ex) {
throw new RuntimeException("Unable to load synchronize peer bindings.", ex);
}
}
/**
* Retrieves the appropriate peer instance for a given object
* Class. Returns null in the event that no peer is provided
* to support the specified class.
*
* @param objectClass the supported object class
* @param searchSuperClasses flag indicating whether superclasses
* of objectClass should be searched for peers if
* none can be found for objectClass itself
* @return the relevant peer, or null if none can be found
*/
public Object getPeerForObject(Class objectClass, boolean searchSuperClasses) {
Object peer = null;
do {
peer = objectClassNameToPeerMap.get(objectClass.getName());
if (peer != null) {
return peer;
}
if (searchSuperClasses) {
Class[] interfaces = objectClass.getInterfaces();
for (int i = 0; i < interfaces.length; i++) {
peer = getPeerForObject(interfaces[i], true);
if (peer != null) {
return peer;
}
}
objectClass = objectClass.getSuperclass();
}
} while (searchSuperClasses && objectClass != null);
return null;
}
}