org.apache.felix.framework

Class URLHandlers

java.lang.Object

org.apache.felix.framework.URLHandlers

All Implemented Interfaces:

java.net.ContentHandlerFactory, java.net.URLStreamHandlerFactory

class URLHandlers
extends java.lang.Object
implements java.net.URLStreamHandlerFactory, java.net.ContentHandlerFactory

This class is a singleton and implements the stream and content handler factories for all framework instances executing within the JVM. Any calls to retrieve stream or content handlers is routed through this class and it acts as a multiplexer for all framework instances. To achieve this, all framework instances register with this class when they are created so that it can maintain a centralized registry of instances.

When this class receives a request for a stream or content handler, it always returns a proxy handler instead of only returning a proxy if a handler currently exists. This approach is used for three reasons:

1. Potential caching behavior by the JVM of stream handlers does not give you a second chance to provide a handler.
2. Due to the dynamic nature of OSGi services, handlers may appear at any time, so always creating a proxy makes sense.
3. Since these handler factories service all framework instances, some instances may have handlers and others may not, so returning a proxy is the only answer that makes sense.

It is possible to disable the URL Handlers service by setting the framework.service.urlhandlers configuration property to false. When multiple framework instances are in use, if no framework instances enable the URL Handlers service, then the singleton stream and content factories will never be set (i.e., URL.setURLStreamHandlerFactory() and URLConnection.setContentHandlerFactory()). However, if one instance enables URL Handlers service, then the factory methods will be invoked. In that case, framework instances that disable the URL Handlers service will simply not provide that services to their contained bundles, while framework instances with the service enabled will.

Field Summary

Fields

Modifier and Type	Field and Description
private static java.lang.Class[]	CLASS_TYPE
private static java.lang.String	DEFAULT_STREAM_HANDLER_PACKAGE
private static java.util.Map	m_builtIn
private static java.util.Map	m_classloaderToFrameworkLists
private static java.util.Map	m_contentHandlerCache
private static java.net.ContentHandlerFactory	m_contentHandlerFactory
private static int	m_counter
private static java.util.List	m_frameworks
private static URLHandlers	m_handler
private static java.util.Map	m_handlerToURL
private static boolean	m_loaded
private static java.lang.Object	m_rootURLHandlers
private static SecureAction	m_secureAction
private static SecurityManagerEx	m_sm
private static java.util.Map	m_streamHandlerCache
private static java.net.URLStreamHandlerFactory	m_streamHandlerFactory
private static java.lang.String	m_streamPkgs
private static java.lang.String	STREAM_HANDLER_PACKAGE_PROP
private static java.lang.Class	URLHANDLERS_CLASS

Constructor Summary

Constructors

Modifier	Constructor and Description
private	URLHandlers() Only one instance of this class is created per classloader and that one instance is registered as the stream and content handler factories for the JVM.

Method Summary

Modifier and Type	Method and Description
private java.lang.Object	addToCache(java.util.Map cache, java.lang.String key, java.lang.Object value)
private java.net.URLStreamHandler	addToCache(java.lang.String protocol, java.net.URLStreamHandler result)
private java.net.ContentHandler	addToContentCache(java.lang.String mimeType, java.net.ContentHandler handler)
private java.net.URLStreamHandler	addToStreamCache(java.lang.String protocol, java.net.URLStreamHandler handler)
java.net.ContentHandler	createContentHandler(java.lang.String mimeType) This is a method implementation for the ContentHandlerFactory interface.
java.net.URLStreamHandler	createURLStreamHandler(java.lang.String protocol) This is a method implementation for the URLStreamHandlerFactory interface.
private java.net.URLStreamHandler	getBuiltInStreamHandler(java.lang.String protocol, java.net.URLStreamHandlerFactory factory)
static java.lang.Object	getFrameworkFromContext() This method returns the system bundle context for the caller.
private java.net.ContentHandler	getFromContentCache(java.lang.String mimeType)
private java.net.URLStreamHandler	getFromStreamCache(java.lang.String protocol)
private void	init(java.lang.String protocol, java.net.URLStreamHandlerFactory factory)
private java.net.URLStreamHandler	loadBuiltInStreamHandler(java.lang.String protocol, java.lang.ClassLoader classLoader)
static void	registerFrameworkInstance(java.lang.Object framework, boolean enable) Static method that adds a framework instance to the centralized instance registry.
(package private) static void	registerFrameworkListsForContextSearch(java.lang.ClassLoader index, java.util.List frameworkLists)
static void	unregisterFrameworkInstance(java.lang.Object framework) Static method that removes a framework instance from the centralized instance registry.
(package private) static void	unregisterFrameworkListsForContextSearch(java.lang.ClassLoader index)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

CLASS_TYPE

private static final java.lang.Class[] CLASS_TYPE

URLHANDLERS_CLASS

private static final java.lang.Class URLHANDLERS_CLASS

m_secureAction

private static final SecureAction m_secureAction

m_sm

private static volatile SecurityManagerEx m_sm

m_handler

private static volatile URLHandlers m_handler

m_classloaderToFrameworkLists

private static final java.util.Map m_classloaderToFrameworkLists

m_frameworks

private static final java.util.List m_frameworks

m_counter

private static int m_counter

m_contentHandlerCache

private static java.util.Map m_contentHandlerCache

m_streamHandlerCache

private static java.util.Map m_streamHandlerCache

m_streamHandlerFactory

private static java.net.URLStreamHandlerFactory m_streamHandlerFactory

m_contentHandlerFactory

private static java.net.ContentHandlerFactory m_contentHandlerFactory

STREAM_HANDLER_PACKAGE_PROP

private static final java.lang.String STREAM_HANDLER_PACKAGE_PROP

See Also:

Constant Field Values

DEFAULT_STREAM_HANDLER_PACKAGE

private static final java.lang.String DEFAULT_STREAM_HANDLER_PACKAGE

See Also:

Constant Field Values

m_rootURLHandlers

private static java.lang.Object m_rootURLHandlers

m_streamPkgs

private static final java.lang.String m_streamPkgs

m_builtIn

private static final java.util.Map m_builtIn

m_loaded

private static final boolean m_loaded

m_handlerToURL

private static final java.util.Map m_handlerToURL

Constructor Detail

URLHandlers

private URLHandlers()

Only one instance of this class is created per classloader and that one instance is registered as the stream and content handler factories for the JVM. Unless, we already register one from a different classloader. In this case we attach to this root.

Method Detail

init

private void init(java.lang.String protocol,
                  java.net.URLStreamHandlerFactory factory)

registerFrameworkListsForContextSearch

static void registerFrameworkListsForContextSearch(java.lang.ClassLoader index,
                                                   java.util.List frameworkLists)

unregisterFrameworkListsForContextSearch

static void unregisterFrameworkListsForContextSearch(java.lang.ClassLoader index)

getBuiltInStreamHandler

private java.net.URLStreamHandler getBuiltInStreamHandler(java.lang.String protocol,
                                                          java.net.URLStreamHandlerFactory factory)

loadBuiltInStreamHandler

private java.net.URLStreamHandler loadBuiltInStreamHandler(java.lang.String protocol,
                                                           java.lang.ClassLoader classLoader)

addToCache

private java.net.URLStreamHandler addToCache(java.lang.String protocol,
                                             java.net.URLStreamHandler result)

createURLStreamHandler

public java.net.URLStreamHandler createURLStreamHandler(java.lang.String protocol)

This is a method implementation for the URLStreamHandlerFactory interface. It simply creates a stream handler proxy object for the specified protocol. It caches the returned proxy; therefore, subsequent requests for the same protocol will receive the same handler proxy.

Specified by:

createURLStreamHandler in interface java.net.URLStreamHandlerFactory

Parameters:

protocol - the protocol for which a stream handler should be returned.

Returns:

a stream handler proxy for the specified protocol.

createContentHandler

public java.net.ContentHandler createContentHandler(java.lang.String mimeType)

This is a method implementation for the ContentHandlerFactory interface. It simply creates a content handler proxy object for the specified mime type. It caches the returned proxy; therefore, subsequent requests for the same content type will receive the same handler proxy.

Specified by:

createContentHandler in interface java.net.ContentHandlerFactory

Parameters:

mimeType - the mime type for which a content handler should be returned.

Returns:

a content handler proxy for the specified mime type.

addToContentCache

private java.net.ContentHandler addToContentCache(java.lang.String mimeType,
                                                  java.net.ContentHandler handler)

getFromContentCache

private java.net.ContentHandler getFromContentCache(java.lang.String mimeType)

addToStreamCache

private java.net.URLStreamHandler addToStreamCache(java.lang.String protocol,
                                                   java.net.URLStreamHandler handler)

getFromStreamCache

private java.net.URLStreamHandler getFromStreamCache(java.lang.String protocol)

addToCache

private java.lang.Object addToCache(java.util.Map cache,
                                    java.lang.String key,
                                    java.lang.Object value)

registerFrameworkInstance

public static void registerFrameworkInstance(java.lang.Object framework,
                                             boolean enable)

Static method that adds a framework instance to the centralized instance registry.

Parameters:

framework - the framework instance to be added to the instance registry.

enable - a flag indicating whether or not the framework wants to enable the URL Handlers service.

unregisterFrameworkInstance

public static void unregisterFrameworkInstance(java.lang.Object framework)

Static method that removes a framework instance from the centralized instance registry.

Parameters:

framework - the framework instance to be removed from the instance registry.

getFrameworkFromContext

public static java.lang.Object getFrameworkFromContext()

This method returns the system bundle context for the caller. It determines the appropriate system bundle by retrieving the class call stack and find the first class that is loaded from a bundle. It then checks to see which of the registered framework instances owns the class and returns its system bundle context.

Returns:

the system bundle context associated with the caller or null if no associated framework was found.