524 lines
21 KiB
Java
524 lines
21 KiB
Java
/*
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* Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package com.sun.xml.internal.ws.util;
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import com.sun.istack.internal.NotNull;
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import com.sun.istack.internal.Nullable;
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import com.sun.xml.internal.ws.api.Component;
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import com.sun.xml.internal.ws.api.ComponentEx;
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import com.sun.xml.internal.ws.api.server.ContainerResolver;
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import java.io.BufferedReader;
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import java.io.IOException;
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import java.io.InputStream;
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import java.io.InputStreamReader;
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import java.lang.reflect.Array;
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import java.net.URL;
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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.Collection;
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import java.util.Collections;
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import java.util.Enumeration;
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import java.util.Iterator;
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import java.util.List;
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import java.util.NoSuchElementException;
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import java.util.Set;
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import java.util.TreeSet;
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import java.util.WeakHashMap;
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import java.util.concurrent.ConcurrentHashMap;
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/**
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* A simple service-provider lookup mechanism. A <i>service</i> is a
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* well-known set of interfaces and (usually abstract) classes. A <i>service
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* provider</i> is a specific implementation of a service. The classes in a
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* provider typically implement the interfaces and subclass the classes defined
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* in the service itself. Service providers may be installed in an
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* implementation of the Java platform in the form of extensions, that is, jar
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* files placed into any of the usual extension directories. Providers may
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* also be made available by adding them to the applet or application class
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* path or by some other platform-specific means.
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* <p/>
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* <p> In this lookup mechanism a service is represented by an interface or an
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* abstract class. (A concrete class may be used, but this is not
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* recommended.) A provider of a given service contains one or more concrete
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* classes that extend this <i>service class</i> with data and code specific to
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* the provider. This <i>provider class</i> will typically not be the entire
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* provider itself but rather a proxy that contains enough information to
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* decide whether the provider is able to satisfy a particular request together
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* with code that can create the actual provider on demand. The details of
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* provider classes tend to be highly service-specific; no single class or
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* interface could possibly unify them, so no such class has been defined. The
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* only requirement enforced here is that provider classes must have a
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* zero-argument constructor so that they may be instantiated during lookup.
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* <p/>
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* <p> A service provider identifies itself by placing a provider-configuration
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* file in the resource directory <tt>META-INF/services</tt>. The file's name
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* should consist of the fully-qualified name of the abstract service class.
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* The file should contain a list of fully-qualified concrete provider-class
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* names, one per line. Space and tab characters surrounding each name, as
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* well as blank lines, are ignored. The comment character is <tt>'#'</tt>
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* (<tt>0x23</tt>); on each line all characters following the first comment
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* character are ignored. The file must be encoded in UTF-8.
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* <p/>
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* <p> If a particular concrete provider class is named in more than one
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* configuration file, or is named in the same configuration file more than
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* once, then the duplicates will be ignored. The configuration file naming a
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* particular provider need not be in the same jar file or other distribution
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* unit as the provider itself. The provider must be accessible from the same
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* class loader that was initially queried to locate the configuration file;
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* note that this is not necessarily the class loader that found the file.
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* <p/>
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* <p> <b>Example:</b> Suppose we have a service class named
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* <tt>java.io.spi.CharCodec</tt>. It has two abstract methods:
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* <p/>
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* <pre>
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* public abstract CharEncoder getEncoder(String encodingName);
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* public abstract CharDecoder getDecoder(String encodingName);
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* </pre>
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* <p/>
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* Each method returns an appropriate object or <tt>null</tt> if it cannot
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* translate the given encoding. Typical <tt>CharCodec</tt> providers will
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* support more than one encoding.
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* <p/>
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* <p> If <tt>sun.io.StandardCodec</tt> is a provider of the <tt>CharCodec</tt>
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* service then its jar file would contain the file
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* <tt>META-INF/services/java.io.spi.CharCodec</tt>. This file would contain
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* the single line:
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* <p/>
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* <pre>
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* sun.io.StandardCodec # Standard codecs for the platform
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* </pre>
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* <p/>
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* To locate an codec for a given encoding name, the internal I/O code would
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* do something like this:
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* <p/>
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* <pre>
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* CharEncoder getEncoder(String encodingName) {
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* for( CharCodec cc : ServiceFinder.find(CharCodec.class) ) {
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* CharEncoder ce = cc.getEncoder(encodingName);
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* if (ce != null)
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* return ce;
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* }
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* return null;
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* }
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* </pre>
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* <p/>
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* The provider-lookup mechanism always executes in the security context of the
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* caller. Trusted system code should typically invoke the methods in this
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* class from within a privileged security context.
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*
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* @author Mark Reinhold
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* @version 1.11, 03/12/19
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* @since 1.3
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*/
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public final class ServiceFinder<T> implements Iterable<T> {
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private static final String prefix = "META-INF/services/";
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private static WeakHashMap<ClassLoader, ConcurrentHashMap<String, ServiceName[]>> serviceNameCache
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= new WeakHashMap<ClassLoader, ConcurrentHashMap<String, ServiceName[]>>();
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private final Class<T> serviceClass;
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private final @Nullable ClassLoader classLoader;
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private final @Nullable ComponentEx component;
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private static class ServiceName {
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final String className;
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final URL config;
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public ServiceName(String className, URL config) {
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this.className = className;
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this.config = config;
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}
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}
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public static <T> ServiceFinder<T> find(@NotNull Class<T> service, @Nullable ClassLoader loader, Component component) {
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return new ServiceFinder<T>(service, loader, component);
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}
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public static <T> ServiceFinder<T> find(@NotNull Class<T> service, Component component) {
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return find(service,Thread.currentThread().getContextClassLoader(),component);
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}
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/**
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* Locates and incrementally instantiates the available providers of a
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* given service using the given class loader.
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* <p/>
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* <p> This method transforms the name of the given service class into a
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* provider-configuration filename as described above and then uses the
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* <tt>getResources</tt> method of the given class loader to find all
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* available files with that name. These files are then read and parsed to
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* produce a list of provider-class names. The iterator that is returned
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* uses the given class loader to lookup and then instantiate each element
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* of the list.
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* <p/>
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* <p> Because it is possible for extensions to be installed into a running
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* Java virtual machine, this method may return different results each time
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* it is invoked. <p>
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*
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* @param service The service's abstract service class
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* @param loader The class loader to be used to load provider-configuration files
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* and instantiate provider classes, or <tt>null</tt> if the system
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* class loader (or, failing that the bootstrap class loader) is to
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* be used
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* @throws ServiceConfigurationError If a provider-configuration file violates the specified format
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* or names a provider class that cannot be found and instantiated
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* @see #find(Class)
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*/
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public static <T> ServiceFinder<T> find(@NotNull Class<T> service, @Nullable ClassLoader loader) {
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return find(service, loader, ContainerResolver.getInstance().getContainer());
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}
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/**
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* Locates and incrementally instantiates the available providers of a
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* given service using the context class loader. This convenience method
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* is equivalent to
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* <p/>
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* <pre>
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* ClassLoader cl = Thread.currentThread().getContextClassLoader();
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* return Service.providers(service, cl);
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* </pre>
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*
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* @param service The service's abstract service class
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*
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* @throws ServiceConfigurationError If a provider-configuration file violates the specified format
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* or names a provider class that cannot be found and instantiated
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* @see #find(Class, ClassLoader)
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*/
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public static <T> ServiceFinder<T> find(Class<T> service) {
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return find(service,Thread.currentThread().getContextClassLoader());
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}
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private ServiceFinder(Class<T> service, ClassLoader loader, Component component) {
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this.serviceClass = service;
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this.classLoader = loader;
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this.component = getComponentEx(component);
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}
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private static ServiceName[] serviceClassNames(Class serviceClass, ClassLoader classLoader) {
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ArrayList<ServiceName> l = new ArrayList<ServiceName>();
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for (Iterator<ServiceName> it = new ServiceNameIterator(serviceClass,classLoader);it.hasNext();) l.add(it.next());
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return l.toArray(new ServiceName[l.size()]);
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}
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/**
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* Returns discovered objects incrementally.
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*
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* @return An <tt>Iterator</tt> that yields provider objects for the given
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* service, in some arbitrary order. The iterator will throw a
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* <tt>ServiceConfigurationError</tt> if a provider-configuration
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* file violates the specified format or if a provider class cannot
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* be found and instantiated.
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*/
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@SuppressWarnings("unchecked")
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public Iterator<T> iterator() {
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Iterator<T> it = new LazyIterator<T>(serviceClass,classLoader);
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return component != null ?
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new CompositeIterator<T>(
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component.getIterableSPI(serviceClass).iterator(),it) :
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it;
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}
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/**
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* Returns discovered objects all at once.
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*
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* @return
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* can be empty but never null.
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*
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* @throws ServiceConfigurationError
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*/
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public T[] toArray() {
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List<T> result = new ArrayList<T>();
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for (T t : this) {
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result.add(t);
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}
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return result.toArray((T[])Array.newInstance(serviceClass,result.size()));
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}
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private static void fail(Class service, String msg, Throwable cause)
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throws ServiceConfigurationError {
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ServiceConfigurationError sce
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= new ServiceConfigurationError(service.getName() + ": " + msg);
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sce.initCause(cause);
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throw sce;
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}
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private static void fail(Class service, String msg)
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throws ServiceConfigurationError {
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throw new ServiceConfigurationError(service.getName() + ": " + msg);
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}
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private static void fail(Class service, URL u, int line, String msg)
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throws ServiceConfigurationError {
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fail(service, u + ":" + line + ": " + msg);
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}
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/**
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* Parse a single line from the given configuration file, adding the name
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* on the line to both the names list and the returned set iff the name is
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* not already a member of the returned set.
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*/
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private static int parseLine(Class service, URL u, BufferedReader r, int lc,
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List<String> names, Set<String> returned)
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throws IOException, ServiceConfigurationError {
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String ln = r.readLine();
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if (ln == null) {
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return -1;
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}
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int ci = ln.indexOf('#');
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if (ci >= 0) ln = ln.substring(0, ci);
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ln = ln.trim();
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int n = ln.length();
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if (n != 0) {
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if ((ln.indexOf(' ') >= 0) || (ln.indexOf('\t') >= 0))
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fail(service, u, lc, "Illegal configuration-file syntax");
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int cp = ln.codePointAt(0);
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if (!Character.isJavaIdentifierStart(cp))
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fail(service, u, lc, "Illegal provider-class name: " + ln);
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for (int i = Character.charCount(cp); i < n; i += Character.charCount(cp)) {
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cp = ln.codePointAt(i);
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if (!Character.isJavaIdentifierPart(cp) && (cp != '.'))
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fail(service, u, lc, "Illegal provider-class name: " + ln);
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}
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if (!returned.contains(ln)) {
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names.add(ln);
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returned.add(ln);
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}
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}
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return lc + 1;
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}
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/**
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* Parse the content of the given URL as a provider-configuration file.
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*
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* @param service The service class for which providers are being sought;
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* used to construct error detail strings
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* @param u The URL naming the configuration file to be parsed
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* @param returned A Set containing the names of provider classes that have already
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* been returned. This set will be updated to contain the names
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* that will be yielded from the returned <tt>Iterator</tt>.
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* @return A (possibly empty) <tt>Iterator</tt> that will yield the
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* provider-class names in the given configuration file that are
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* not yet members of the returned set
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* @throws ServiceConfigurationError If an I/O error occurs while reading from the given URL, or
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* if a configuration-file format error is detected
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*/
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@SuppressWarnings({"StatementWithEmptyBody"})
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private static Iterator<String> parse(Class service, URL u, Set<String> returned)
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throws ServiceConfigurationError {
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InputStream in = null;
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BufferedReader r = null;
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ArrayList<String> names = new ArrayList<String>();
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try {
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in = u.openStream();
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r = new BufferedReader(new InputStreamReader(in, "utf-8"));
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int lc = 1;
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while ((lc = parseLine(service, u, r, lc, names, returned)) >= 0) ;
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} catch (IOException x) {
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fail(service, ": " + x);
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} finally {
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try {
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if (r != null) r.close();
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if (in != null) in.close();
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} catch (IOException y) {
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fail(service, ": " + y);
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}
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}
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return names.iterator();
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}
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private static ComponentEx getComponentEx(Component component) {
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if (component instanceof ComponentEx)
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return (ComponentEx) component;
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return component != null ? new ComponentExWrapper(component) : null;
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}
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private static class ComponentExWrapper implements ComponentEx {
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private final Component component;
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public ComponentExWrapper(Component component) {
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this.component = component;
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}
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public <S> S getSPI(Class<S> spiType) {
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return component.getSPI(spiType);
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}
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public <S> Iterable<S> getIterableSPI(Class<S> spiType) {
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S item = getSPI(spiType);
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if (item != null) {
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Collection<S> c = Collections.singletonList(item);
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return c;
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}
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return Collections.emptySet();
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}
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}
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private static class CompositeIterator<T> implements Iterator<T> {
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private final Iterator<Iterator<T>> it;
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private Iterator<T> current = null;
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public CompositeIterator(Iterator<T>... iterators) {
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it = Arrays.asList(iterators).iterator();
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}
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public boolean hasNext() {
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if (current != null && current.hasNext())
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return true;
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while (it.hasNext()) {
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current = it.next();
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if (current.hasNext())
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return true;
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}
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return false;
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}
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public T next() {
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if (!hasNext())
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throw new NoSuchElementException();
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return current.next();
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}
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public void remove() {
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throw new UnsupportedOperationException();
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}
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}
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/**
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* Private inner class implementing fully-lazy provider lookup
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*/
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private static class ServiceNameIterator implements Iterator<ServiceName> {
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Class service;
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@Nullable ClassLoader loader;
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Enumeration<URL> configs = null;
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Iterator<String> pending = null;
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Set<String> returned = new TreeSet<String>();
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String nextName = null;
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URL currentConfig = null;
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private ServiceNameIterator(Class service, ClassLoader loader) {
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this.service = service;
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this.loader = loader;
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}
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public boolean hasNext() throws ServiceConfigurationError {
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if (nextName != null) {
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return true;
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}
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if (configs == null) {
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try {
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String fullName = prefix + service.getName();
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if (loader == null)
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configs = ClassLoader.getSystemResources(fullName);
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else
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configs = loader.getResources(fullName);
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} catch (IOException x) {
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fail(service, ": " + x);
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}
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}
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while ((pending == null) || !pending.hasNext()) {
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if (!configs.hasMoreElements()) {
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return false;
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}
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currentConfig = configs.nextElement();
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pending = parse(service, currentConfig, returned);
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}
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nextName = pending.next();
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return true;
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}
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public ServiceName next() throws ServiceConfigurationError {
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if (!hasNext()) {
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throw new NoSuchElementException();
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}
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String cn = nextName;
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nextName = null;
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return new ServiceName(cn, currentConfig);
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}
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public void remove() {
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throw new UnsupportedOperationException();
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}
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}
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private static class LazyIterator<T> implements Iterator<T> {
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Class<T> service;
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@Nullable ClassLoader loader;
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ServiceName[] names;
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int index;
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private LazyIterator(Class<T> service, ClassLoader loader) {
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this.service = service;
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this.loader = loader;
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this.names = null;
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index = 0;
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}
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@Override
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public boolean hasNext() {
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if (names == null) {
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ConcurrentHashMap<String, ServiceName[]> nameMap = null;
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synchronized(serviceNameCache){ nameMap = serviceNameCache.get(loader); }
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names = (nameMap != null)? nameMap.get(service.getName()) : null;
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if (names == null) {
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names = serviceClassNames(service, loader);
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if (nameMap == null) nameMap = new ConcurrentHashMap<String, ServiceName[]>();
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nameMap.put(service.getName(), names);
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synchronized(serviceNameCache){ serviceNameCache.put(loader,nameMap); }
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}
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}
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return (index < names.length);
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}
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@Override
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public T next() {
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if (!hasNext()) throw new NoSuchElementException();
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ServiceName sn = names[index++];
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String cn = sn.className;
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|
URL currentConfig = sn.config;
|
|
try {
|
|
return service.cast(Class.forName(cn, true, loader).newInstance());
|
|
} catch (ClassNotFoundException x) {
|
|
fail(service, "Provider " + cn + " is specified in "+currentConfig+" but not found");
|
|
} catch (Exception x) {
|
|
fail(service, "Provider " + cn + " is specified in "+currentConfig+"but could not be instantiated: " + x, x);
|
|
}
|
|
return null; /* This cannot happen */
|
|
}
|
|
|
|
@Override
|
|
public void remove() {
|
|
throw new UnsupportedOperationException();
|
|
}
|
|
|
|
}
|
|
}
|