Make the URLStreamHandler as lazy as possible

URLStreamHandlerFactoryImpl currently opens a service tracker
unconditionally for URLStreamHandlerService to discover registered
handlers. This leads to any handler being fetched eagerly instead of
when it is required.

This changes the handling in a way where it is as lazy as possible by

- not open a tracker until a protocol is requested
- use a service tracker with a specific protocol filter in proxy
- only fetch the service when it is first used

bundles/org.eclipse.osgi/container/src/org/eclipse/osgi/internal/url/URLStreamHandlerFactoryImpl.java

@@ -15,21 +15,22 @@
 package org.eclipse.osgi.internal.url;
 
 import java.lang.reflect.Method;
-import java.net.*;
+import java.net.URL;
+import java.net.URLStreamHandler;
+import java.net.URLStreamHandlerFactory;
 import java.security.AccessController;
-import java.util.*;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+import java.util.StringTokenizer;
+import java.util.concurrent.ConcurrentHashMap;
 import org.eclipse.osgi.framework.log.FrameworkLogEntry;
 import org.eclipse.osgi.framework.util.SecureAction;
 import org.eclipse.osgi.internal.framework.EquinoxContainer;
 import org.eclipse.osgi.internal.location.EquinoxLocations;
-import org.eclipse.osgi.internal.messages.Msg;
 import org.eclipse.osgi.storage.url.BundleResourceHandler;
-import org.eclipse.osgi.util.NLS;
 import org.osgi.framework.BundleContext;
-import org.osgi.framework.ServiceReference;
-import org.osgi.service.url.URLConstants;
-import org.osgi.service.url.URLStreamHandlerService;
-import org.osgi.util.tracker.ServiceTracker;
 
 /**
  * This class contains the URL stream handler factory for the OSGi framework.
@@ -40,10 +41,8 @@ public class URLStreamHandlerFactoryImpl extends MultiplexingFactory implements
  public static final String PROTOCOL_REFERENCE = "reference"; //$NON-NLS-1$
  static final SecureAction secureAction = AccessController.doPrivileged(SecureAction.createSecureAction());
 
- private ServiceTracker<URLStreamHandlerService, URLStreamHandlerService> handlerTracker;
-
  private static final List<Class<?>> ignoredClasses = Arrays.asList(new Class<?>[] {MultiplexingURLStreamHandler.class, URLStreamHandlerFactoryImpl.class, URL.class});
- private Map<String, URLStreamHandler> proxies;
+ private Map<String, URLStreamHandlerProxy> proxies;
  private URLStreamHandlerFactory parentFactory;
  private ThreadLocal<List<String>> creatingProtocols = new ThreadLocal<>();
 
@@ -54,10 +53,7 @@ public class URLStreamHandlerFactoryImpl extends MultiplexingFactory implements
  */
  public URLStreamHandlerFactoryImpl(BundleContext context, EquinoxContainer container) {
  super(context, container);
-
- proxies = new Hashtable<>(15);
- handlerTracker = new ServiceTracker<>(context, URLSTREAMHANDLERCLASS, null);
- handlerTracker.open();
+ proxies = new ConcurrentHashMap<>();
  }
 
  private Class<?> getBuiltIn(String protocol, String builtInHandlers) {
@@ -154,35 +150,13 @@ public URLStreamHandler createInternalURLStreamHandler(String protocol) {
  if (frameworkHandler != null) {
  return frameworkHandler;
  }
-
  //Now we check the service registry
- //first check to see if the handler is in the cache
- URLStreamHandlerProxy handler = (URLStreamHandlerProxy) proxies.get(protocol);
- if (handler != null)
- return (handler);
- //look through the service registry for a URLStramHandler registered for this protocol
- ServiceReference<URLStreamHandlerService>[] serviceReferences = handlerTracker.getServiceReferences();
- if (serviceReferences == null)
- return null;
- for (ServiceReference<URLStreamHandlerService> serviceReference : serviceReferences) {
- Object prop = serviceReference.getProperty(URLConstants.URL_HANDLER_PROTOCOL);
- if (prop instanceof String)
- prop = new String[] {(String) prop}; // TODO should this be a warning?
- if (!(prop instanceof String[])) {
- String message = NLS.bind(Msg.URL_HANDLER_INCORRECT_TYPE, new Object[]{URLConstants.URL_HANDLER_PROTOCOL, URLSTREAMHANDLERCLASS, serviceReference.getBundle()});
- container.getLogServices().log(EquinoxContainer.NAME, FrameworkLogEntry.WARNING, message, null);
- continue;
- }
- String[] protocols = (String[]) prop;
- for (String candidateProtocol : protocols) {
- if (candidateProtocol.equals(protocol)) {
- handler = new URLStreamHandlerProxy(protocol, serviceReference, context);
- proxies.put(protocol, handler);
- return (handler);
- }
- }
+ URLStreamHandlerProxy handler = proxies.computeIfAbsent(protocol, p -> new URLStreamHandlerProxy(p, context));
+ if (handler.isActive()) {
+ return handler;
  }
  return null;
+
  }
 
  protected URLStreamHandler findAuthorizedURLStreamHandler(String protocol) {