org.apache.felix.framework.URLHandlersContentHandlerProxy Maven / Gradle / Ivy
/*
* 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.felix.framework;
import java.io.IOException;
import java.net.ContentHandler;
import java.net.ContentHandlerFactory;
import java.net.URLConnection;
import java.util.HashMap;
import java.util.Map;
import java.util.StringTokenizer;
import org.apache.felix.framework.util.SecureAction;
/**
*
* This class implements a content handler proxy. When the content handler
* proxy instance is created, it is associated with a particular mime type
* and will answer all future requests for content of that type. It does
* not directly handle the content requests, but delegates the requests to
* an underlying content handler service.
*
*
* The proxy for a particular mime type is used for all framework instances
* that may contain their own content handler services. When performing a
* content handler operation, the proxy retrieves the handler service from
* the framework instance associated with the current call stack and delegates
* the call to the handler service.
*
*
* The proxy will create simple content handler service trackers for each
* framework instance. The trackers will listen to service events in its
* respective framework instance to maintain a reference to the "best"
* content handler service at any given time.
*
**/
class URLHandlersContentHandlerProxy extends ContentHandler
{
private static final Class[] STRING_TYPES = new Class[]{String.class};
private static final String CONTENT_HANDLER_PACKAGE_PROP = "java.content.handler.pkgs";
private static final String DEFAULT_CONTENT_HANDLER_PACKAGE = "sun.net.www.content|com.ibm.oti.net.www.content|gnu.java.net.content|org.apache.harmony.luni.internal.net.www.content|COM.newmonics.www.content";
private static final Map m_builtIn = new HashMap();
private static final String m_pkgs;
static
{
String pkgs = new SecureAction().getSystemProperty(CONTENT_HANDLER_PACKAGE_PROP, "");
m_pkgs = (pkgs.equals(""))
? DEFAULT_CONTENT_HANDLER_PACKAGE
: pkgs + "|" + DEFAULT_CONTENT_HANDLER_PACKAGE;
}
private final ContentHandlerFactory m_factory;
private final String m_mimeType;
private final SecureAction m_action;
public URLHandlersContentHandlerProxy(String mimeType, SecureAction action,
ContentHandlerFactory factory)
{
m_mimeType = mimeType;
m_action = action;
m_factory = factory;
}
//
// ContentHandler interface method.
//
public Object getContent(URLConnection urlc) throws IOException
{
ContentHandler svc = getContentHandlerService();
if (svc == null)
{
return urlc.getInputStream();
}
return svc.getContent(urlc);
}
/**
*
* Private method to retrieve the content handler service from the
* framework instance associated with the current call stack. A
* simple service tracker is created and cached for the associated
* framework instance when this method is called.
*
* @return the content handler service from the framework instance
* associated with the current call stack or null
* is no service is available.
**/
private ContentHandler getContentHandlerService()
{
// Get the framework instance associated with call stack.
Object framework = URLHandlers.getFrameworkFromContext();
if (framework == null)
{
return getBuiltIn();
}
try
{
ContentHandler service;
if (framework instanceof Felix)
{
service = (ContentHandler) ((Felix) framework).getContentHandlerService(m_mimeType);
}
else
{
service = (ContentHandler) m_action.invoke(
m_action.getDeclaredMethod(framework.getClass(), "getContentHandlerService", STRING_TYPES),
framework, new Object[]{m_mimeType});
}
return (service == null) ? getBuiltIn() : service;
}
catch (Exception ex)
{
// TODO: log this or something
ex.printStackTrace();
return null;
}
}
private ContentHandler getBuiltIn()
{
synchronized (m_builtIn)
{
if (m_builtIn.containsKey(m_mimeType))
{
return (ContentHandler) m_builtIn.get(m_mimeType);
}
}
if (m_factory != null)
{
ContentHandler result = m_factory.createContentHandler(m_mimeType);
if (result != null)
{
return addToCache(m_mimeType, result);
}
}
// Check for built-in handlers for the mime type.
// Remove periods, slashes, and dashes from mime type.
String fixedType = m_mimeType.replace('.', '_').replace('/', '.').replace('-', '_');
// Iterate over built-in packages.
StringTokenizer pkgTok = new StringTokenizer(m_pkgs, "| ");
while (pkgTok.hasMoreTokens())
{
String pkg = pkgTok.nextToken().trim();
String className = pkg + "." + fixedType;
try
{
// If a built-in handler is found then cache and return it
Class handler = m_action.forName(className, null);
if (handler != null)
{
return addToCache(m_mimeType,
(ContentHandler) handler.newInstance());
}
}
catch (Exception ex)
{
// This could be a class not found exception or an
// instantiation exception, not much we can do in either
// case other than ignore it.
}
}
return addToCache(m_mimeType, null);
}
private synchronized ContentHandler addToCache(String mimeType, ContentHandler handler)
{
if (!m_builtIn.containsKey(mimeType))
{
m_builtIn.put(mimeType, handler);
return handler;
}
return (ContentHandler) m_builtIn.get(mimeType);
}
}