[jboss-svn-commits] JBoss Common SVN: r3768 - in arquillian/trunk/impl-base/src/main/java/org/jboss/arquillian/impl: util and 1 other directory.
jboss-svn-commits at lists.jboss.org
jboss-svn-commits at lists.jboss.org
Mon Nov 23 09:16:32 EST 2009
Author: aslak
Date: 2009-11-23 09:16:31 -0500 (Mon, 23 Nov 2009)
New Revision: 3768
Added:
arquillian/trunk/impl-base/src/main/java/org/jboss/arquillian/impl/util/
arquillian/trunk/impl-base/src/main/java/org/jboss/arquillian/impl/util/DefaultServiceLoader.java
Log:
ARQ-27 Ripped out DefaultServiceLoader from WELD
Added: arquillian/trunk/impl-base/src/main/java/org/jboss/arquillian/impl/util/DefaultServiceLoader.java
===================================================================
--- arquillian/trunk/impl-base/src/main/java/org/jboss/arquillian/impl/util/DefaultServiceLoader.java (rev 0)
+++ arquillian/trunk/impl-base/src/main/java/org/jboss/arquillian/impl/util/DefaultServiceLoader.java 2009-11-23 14:16:31 UTC (rev 3768)
@@ -0,0 +1,297 @@
+/*
+ * JBoss, Home of Professional Open Source
+ * Copyright 2008, Red Hat Middleware LLC, and individual contributors
+ * by the @authors tag. See the copyright.txt in the distribution for a
+ * full listing of individual contributors.
+ *
+ * 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 org.jboss.arquillian.impl.util;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.lang.reflect.Constructor;
+import java.net.URL;
+import java.util.Enumeration;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.Set;
+
+/**
+ * This class handles looking up service providers on the class path. It
+ * implements the <a href="http://java.sun.com/javase/6/docs/technotes/guides/jar/jar.html#Service%20Provider"
+ * >Service Provider section of the JAR File Specification</a>.
+ *
+ * The Service Provider programmatic lookup was not specified prior to Java 6 so
+ * this interface allows use of the specification prior to Java 6.
+ *
+ * The API is copied from <a
+ * href="http://java.sun.com/javase/6/docs/api/java/util/ServiceLoader.html"
+ * >java.util.ServiceLoader</a>
+ *
+ * @author Pete Muir
+ * @author <a href="mailto:dev at avalon.apache.org">Avalon Development Team</a>
+ */
+public class DefaultServiceLoader<S> implements Iterable<S>
+{
+
+ private static final String SERVICES = "META-INF/services";
+
+ /**
+ * Creates a new service loader for the given service type, using the current
+ * thread's context class loader.
+ *
+ * An invocation of this convenience method of the form
+ *
+ * {@code ServiceLoader.load(service)</code>}
+ *
+ * is equivalent to
+ *
+ * <code>ServiceLoader.load(service,
+ * Thread.currentThread().getContextClassLoader())</code>
+ *
+ * @param service The interface or abstract class representing the service
+ * @return A new service loader
+ */
+ public static <S> DefaultServiceLoader<S> load(Class<S> service)
+ {
+ return load(SERVICES, service, Thread.currentThread().getContextClassLoader());
+ }
+
+ public static <S> DefaultServiceLoader<S> load(String directoryName, Class<S> service)
+ {
+ return load(directoryName, service, Thread.currentThread().getContextClassLoader());
+ }
+
+ public static <S> DefaultServiceLoader<S> load(String directoryName, Class<S> service, ClassLoader loader)
+ {
+ if (loader == null)
+ {
+ loader = service.getClassLoader();
+ }
+ return new DefaultServiceLoader<S>(directoryName, service, loader);
+ }
+
+ /**
+ * Creates a new service loader for the given service type and class loader.
+ *
+ * @param service The interface or abstract class representing the service
+ * @param loader The class loader to be used to load provider-configuration
+ * files and provider classes, or null if the system class loader
+ * (or, failing that, the bootstrap class loader) is to be used
+ * @return A new service loader
+ */
+ public static <S> DefaultServiceLoader<S> load(Class<S> service, ClassLoader loader)
+ {
+ return load(SERVICES, service, loader);
+ }
+
+ /**
+ * Creates a new service loader for the given service type, using the
+ * extension class loader.
+ *
+ * This convenience method simply locates the extension class loader, call it
+ * extClassLoader, and then returns
+ *
+ * <code>ServiceLoader.load(service, extClassLoader)</code>
+ *
+ * If the extension class loader cannot be found then the system class loader
+ * is used; if there is no system class loader then the bootstrap class
+ * loader is used.
+ *
+ * This method is intended for use when only installed providers are desired.
+ * The resulting service will only find and load providers that have been
+ * installed into the current Java virtual machine; providers on the
+ * application's class path will be ignored.
+ *
+ * @param service The interface or abstract class representing the service
+ * @return A new service loader
+ */
+ public static <S> DefaultServiceLoader<S> loadInstalled(Class<S> service)
+ {
+ throw new UnsupportedOperationException();
+ }
+
+ private final String serviceFile;
+ private Class<S> expectedType;
+ private final ClassLoader loader;
+
+ private Set<S> providers;
+
+ private DefaultServiceLoader(String prefix, Class<S> service, ClassLoader loader)
+ {
+ this.loader = loader;
+ this.serviceFile = prefix + "/" + service.getName();
+ this.expectedType = service;
+ }
+
+ /**
+ * Clear this loader's provider cache so that all providers will be reloaded.
+ *
+ * After invoking this method, subsequent invocations of the iterator method
+ * will lazily look up and instantiate providers from scratch, just as is
+ * done by a newly-created loader.
+ *
+ * This method is intended for use in situations in which new providers can
+ * be installed into a running Java virtual machine.
+ */
+ public void reload()
+ {
+ providers = new HashSet<S>();
+ Enumeration<URL> enumeration = null;
+ boolean errorOccurred = false;
+
+ try
+ {
+ enumeration = loader.getResources(serviceFile);
+ }
+ catch (IOException ioe)
+ {
+ errorOccurred = true;
+ }
+
+ if (!errorOccurred)
+ {
+ while (enumeration.hasMoreElements())
+ {
+ try
+ {
+ final URL url = enumeration.nextElement();
+ final InputStream is = url.openStream();
+ final BufferedReader reader = new BufferedReader(new InputStreamReader(is, "UTF-8"));
+
+ String line = reader.readLine();
+ while (null != line)
+ {
+ try
+ {
+ final int comment = line.indexOf('#');
+
+ if (comment > -1)
+ {
+ line = line.substring(0, comment);
+ }
+
+ line.trim();
+
+ if (line.length() > 0)
+ {
+ try
+ {
+ Class<?> clazz = loader.loadClass(line);
+ Class<? extends S> serviceClass;
+ try
+ {
+ serviceClass = clazz.asSubclass(expectedType);
+ }
+ catch (ClassCastException e)
+ {
+ throw new IllegalStateException("Extension " + line + " does not implement Extension");
+ }
+ Constructor<? extends S> constructor = serviceClass.getConstructor();
+ if(!constructor.isAccessible()) {
+ constructor.setAccessible(true);
+ }
+ S instance = constructor.newInstance();
+ providers.add(instance);
+ }
+ catch (NoClassDefFoundError e)
+ {
+ throw e;
+ }
+ catch (InstantiationException e)
+ {
+ throw e;
+ }
+ catch (IllegalAccessException e)
+ {
+ throw e;
+ }
+ }
+ }
+ catch (Exception e)
+ {
+ // TODO Don't use exceptions for flow control!
+ // try the next line
+ }
+
+ line = reader.readLine();
+ }
+ }
+ catch (Exception e)
+ {
+ // try the next file
+ }
+ }
+ }
+ }
+
+
+
+ /**
+ * Lazily loads the available providers of this loader's service.
+ *
+ * The iterator returned by this method first yields all of the elements of
+ * the provider cache, in instantiation order. It then lazily loads and
+ * instantiates any remaining providers, adding each one to the cache in
+ * turn.
+ *
+ * To achieve laziness the actual work of parsing the available
+ * provider-configuration files and instantiating providers must be done by
+ * the iterator itself. Its hasNext and next methods can therefore throw a
+ * ServiceConfigurationError if a provider-configuration file violates the
+ * specified format, or if it names a provider class that cannot be found and
+ * instantiated, or if the result of instantiating the class is not
+ * assignable to the service type, or if any other kind of exception or error
+ * is thrown as the next provider is located and instantiated. To write
+ * robust code it is only necessary to catch ServiceConfigurationError when
+ * using a service iterator.
+ *
+ * If such an error is thrown then subsequent invocations of the iterator
+ * will make a best effort to locate and instantiate the next available
+ * provider, but in general such recovery cannot be guaranteed.
+ *
+ * Design Note Throwing an error in these cases may seem extreme. The
+ * rationale for this behavior is that a malformed provider-configuration
+ * file, like a malformed class file, indicates a serious problem with the
+ * way the Java virtual machine is configured or is being used. As such it is
+ * preferable to throw an error rather than try to recover or, even worse,
+ * fail silently.
+ *
+ * The iterator returned by this method does not support removal. Invoking
+ * its remove method will cause an UnsupportedOperationException to be
+ * thrown.
+ *
+ * @return An iterator that lazily loads providers for this loader's service
+ */
+ public Iterator<S> iterator()
+ {
+ if (providers == null)
+ {
+ reload();
+ }
+ return providers.iterator();
+ }
+
+ /**
+ * Returns a string describing this service.
+ *
+ * @return A descriptive string
+ */
+ @Override
+ public String toString()
+ {
+ return "Services for " + serviceFile;
+ }
+
+}
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