fbe85300bf
Co-authored-by: Mandy Chung <mandy.chung@oracle.com> Co-authored-by: Claes Redestad <claes.redestad@oracle.com> Co-authored-by: Mark Reinhold <mark.reinhold@oracle.com> Reviewed-by: plevart, chegar, psandoz, mchung, alanb, dfuchs, naoto, coffeys, weijun
1598 lines
63 KiB
Java
1598 lines
63 KiB
Java
/*
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* Copyright (c) 2005, 2016, 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 java.util;
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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.Constructor;
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import java.lang.reflect.InvocationTargetException;
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import java.lang.reflect.Layer;
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import java.lang.reflect.Method;
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import java.lang.reflect.Modifier;
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import java.lang.reflect.Module;
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import java.net.URL;
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import java.net.URLConnection;
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import java.security.AccessControlContext;
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import java.security.AccessController;
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import java.security.PrivilegedAction;
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import java.security.PrivilegedActionException;
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import java.security.PrivilegedExceptionAction;
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import java.util.function.Consumer;
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import java.util.function.Supplier;
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import java.util.stream.Stream;
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import java.util.stream.StreamSupport;
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import jdk.internal.loader.BootLoader;
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import jdk.internal.misc.JavaLangAccess;
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import jdk.internal.misc.JavaLangReflectModuleAccess;
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import jdk.internal.misc.SharedSecrets;
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import jdk.internal.misc.VM;
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import jdk.internal.module.ServicesCatalog;
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import jdk.internal.module.ServicesCatalog.ServiceProvider;
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import jdk.internal.reflect.CallerSensitive;
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import jdk.internal.reflect.Reflection;
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/**
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* A simple service-provider loading facility.
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*
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* <p> A <i>service</i> is a well-known set of interfaces and (usually
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* abstract) classes. A <i>service provider</i> is a specific implementation
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* of a service. The classes in a provider typically implement the interfaces
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* and subclass the classes defined in the service itself.
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* Providers may be developed and deployed as modules and made available using
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* the application module path. Providers may alternatively be packaged as JAR
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* files and made available by adding them to the application class path. The
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* advantage of developing a provider as a module is that the provider can be
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* fully encapsulated to hide all details of its implementation.
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*
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* <p> For the purpose of loading, a service is represented by a single type,
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* that is, a single interface or abstract class. (A concrete class can be
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* used, but this is not recommended.) A provider of a given service contains
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* one or more concrete classes that extend this <i>service type</i> with data
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* and code specific to the provider. The <i>provider class</i> is typically
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* not the entire provider itself but rather a proxy which contains enough
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* information to decide whether the provider is able to satisfy a particular
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* request together with code that can create the actual provider on demand.
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* The details of provider classes tend to be highly service-specific; no
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* single class or interface could possibly unify them, so no such type is
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* defined here.
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*
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* <p> Providers deployed as explicit modules on the module path are
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* instantiated by a <em>provider factory</em> or directly via the provider's
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* constructor. In the module declaration then the class name specified in the
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* <i>provides</i> clause is a provider factory if it is public and defines a
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* public static no-args method named "{@code provider}". The return type of
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* the method must be assignable to the <i>service</i> type. If the class is
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* not a provider factory then it is public with a public zero-argument
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* constructor. The requirement that the provider factory or provider class
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* be public helps to document the intent that the provider will be
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* instantiated by the service-provider loading facility.
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*
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* <p> As an example, suppose a module declares the following:
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*
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* <pre>{@code
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* provides com.example.CodecSet with com.example.impl.StandardCodecs;
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* provides com.example.CodecSet with com.example.impl.ExtendedCodecsFactory;
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* }</pre>
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*
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* <p> where {@code com.example.CodecSet} is the service type, {@code
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* com.example.impl.StandardCodecs} is a provider class that is public with a
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* public no-args constructor, {@code com.example.impl.ExtendedCodecsFactory}
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* is a public class that defines a public static no-args method named
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* "{@code provider}" with a return type that is {@code CodecSet} or a subtype
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* of. For this example then {@code StandardCodecs}'s no-arg constructor will
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* be used to instantiate {@code StandardCodecs}. {@code ExtendedCodecsFactory}
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* will be treated as a provider factory and {@code
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* ExtendedCodecsFactory.provider()} will be invoked to obtain the provider.
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*
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* <p> Providers deployed on the class path or as {@link
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* java.lang.module.ModuleDescriptor#isAutomatic automatic-modules} on the
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* module path must have a public zero-argument constructor.
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*
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* <p> An application or library using this loading facility and developed
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* and deployed as an explicit module must have an appropriate <i>uses</i>
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* clause in its <i>module descriptor</i> to declare that the module uses
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* implementations of the service. A corresponding requirement is that a
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* provider deployed as a named module must have an appropriate
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* <i>provides</i> clause in its module descriptor to declare that the module
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* provides an implementation of the service. The <i>uses</i> and
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* <i>provides</i> allow consumers of a service to be <i>linked</i> to modules
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* containing providers of the service.
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*
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* <p> A service provider that is packaged as a JAR file for the class path is
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* identified by placing a <i>provider-configuration file</i> in the resource
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* directory <tt>META-INF/services</tt>. The file's name is the fully-qualified
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* <a href="../lang/ClassLoader.html#name">binary name</a> of the service's
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* type. The file contains a list of fully-qualified binary names of concrete
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* provider classes, one per line. Space and tab characters surrounding each
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* name, as well as blank lines, are ignored. The comment character is
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* <tt>'#'</tt> (<tt>'\u0023'</tt>,
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* <font style="font-size:smaller;">NUMBER SIGN</font>); on
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* each line all characters following the first comment character are ignored.
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* The file must be encoded in UTF-8.
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* 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 are 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 visible 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 from which the file was
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* actually loaded.
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*
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* <p> Providers are located and instantiated lazily, that is, on demand. A
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* service loader maintains a cache of the providers that have been loaded so
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* far. Each invocation of the {@link #iterator iterator} method returns an
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* iterator that first yields all of the elements cached from previous
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* iteration, in instantiation order, and then lazily locates and instantiates
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* any remaining providers, adding each one to the cache in turn. Similarly,
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* each invocation of the {@link #stream stream} method returns a stream that
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* first processes all providers loaded by previous stream operations, in load
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* order, and then lazily locates any remaining providers. Caches are cleared
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* via the {@link #reload reload} method.
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*
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* <h2> Locating providers </h2>
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*
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* <p> The {@code load} methods locate providers using a class loader or module
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* {@link Layer layer}. When locating providers using a class loader then
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* providers in both named and unnamed modules may be located. When locating
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* providers using a module layer then only providers in named modules in
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* the layer (or parent layers) are located.
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*
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* <p> When locating providers using a class loader then any providers in named
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* modules defined to the class loader, or any class loader that is reachable
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* via parent delegation, are located. Additionally, providers in module layers
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* other than the {@link Layer#boot() boot} layer, where the module layer
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* contains modules defined to the class loader, or any class loader reachable
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* via parent delegation, are also located. For example, suppose there is a
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* module layer where each module is defined to its own class loader (see {@link
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* Layer#defineModulesWithManyLoaders defineModulesWithManyLoaders}). If the
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* {@code load} method is invoked to locate providers using any of these class
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* loaders for this layer then it will locate all of the providers in that
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* layer, irrespective of their defining class loader.
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*
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* <p> In the case of unnamed modules then the service configuration files are
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* located using the class loader's {@link ClassLoader#getResources(String)
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* ClassLoader.getResources(String)} method. Any providers listed should be
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* visible via the class loader specified to the {@code load} method. If a
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* provider in a named module is listed then it is ignored - this is to avoid
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* duplicates that would otherwise arise when a module has both a
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* <i>provides</i> clause and a service configuration file in {@code
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* META-INF/services} that lists the same provider.
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*
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* <h2> Ordering </h2>
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*
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* <p> Service loaders created to locate providers using a {@code ClassLoader}
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* locate providers as follows:
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* <ul>
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* <li> Providers in named modules are located before providers on the
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* class path (or more generally, unnamed modules). </li>
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*
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* <li> When locating providers in named modules then the service loader
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* will locate providers in modules defined to the class loader, then its
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* parent class loader, its parent parent, and so on to the bootstrap class
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* loader. If a {@code ClassLoader}, or any class loader in the parent
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* delegation chain, defines modules in a custom module {@link Layer} then
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* all providers in that layer are located, irrespective of their class
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* loader. The ordering of modules defined to the same class loader, or the
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* ordering of modules in a layer, is not defined. </li>
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*
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* <li> If a named module declares more than one provider then the providers
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* are located in the order that they appear in the {@code provides} table of
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* the {@code Module} class file attribute ({@code module-info.class}). </li>
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*
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* <li> When locating providers in unnamed modules then the ordering is
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* based on the order that the class loader's {@link
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* ClassLoader#getResources(String) ClassLoader.getResources(String)}
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* method finds the service configuration files. </li>
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* </ul>
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*
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* <p> Service loaders created to locate providers in a module {@link Layer}
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* will first locate providers in the layer, before locating providers in
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* parent layers. Traversal of parent layers is depth-first with each layer
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* visited at most once. For example, suppose L0 is the boot layer, L1 and
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* L2 are custom layers with L0 as their parent. Now suppose that L3 is
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* created with L1 and L2 as the parents (in that order). Using a service
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* loader to locate providers with L3 as the content will locate providers
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* in the following order: L3, L1, L0, L2. The ordering of modules in a layer
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* is not defined.
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*
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* <h2> Selection and filtering </h2>
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*
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* <p> Selecting a provider or filtering providers will usually involve invoking
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* a provider method. Where selection or filtering based on the provider class is
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* needed then it can be done using a {@link #stream() stream}. For example, the
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* following collects the providers that have a specific annotation:
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* <pre>{@code
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* Set<CodecSet> providers = ServiceLoader.load(CodecSet.class)
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* .stream()
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* .filter(p -> p.type().isAnnotationPresent(Managed.class))
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* .map(Provider::get)
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* .collect(Collectors.toSet());
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* }</pre>
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*
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* <h2> Security </h2>
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*
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* <p> Service loaders always execute in the security context of the caller
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* of the iterator or stream methods and may also be restricted by the security
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* context of the caller that created the service loader.
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* Trusted system code should typically invoke the methods in this class, and
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* the methods of the iterators which they return, from within a privileged
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* security context.
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*
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* <h2> Concurrency </h2>
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*
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* <p> Instances of this class are not safe for use by multiple concurrent
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* threads.
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*
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* <h2> Null handling </h2>
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*
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* <p> Unless otherwise specified, passing a {@code null} argument to any
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* method in this class will cause a {@link NullPointerException} to be thrown.
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*
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* <h2> Example </h2>
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* <p> Suppose we have a service type <tt>com.example.CodecSet</tt> which is
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* intended to represent sets of encoder/decoder pairs for some protocol. In
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* this case it is an abstract class with two abstract methods:
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*
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* <blockquote><pre>
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* public abstract Encoder getEncoder(String encodingName);
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* public abstract Decoder getDecoder(String encodingName);</pre></blockquote>
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*
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* Each method returns an appropriate object or <tt>null</tt> if the provider
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* does not support the given encoding. Typical providers support more than
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* one encoding.
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*
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* <p> The <tt>CodecSet</tt> class creates and saves a single service instance
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* at initialization:
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*
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* <pre>{@code
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* private static ServiceLoader<CodecSet> codecSetLoader
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* = ServiceLoader.load(CodecSet.class);
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* }</pre>
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*
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* <p> To locate an encoder for a given encoding name it defines a static
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* factory method which iterates through the known and available providers,
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* returning only when it has located a suitable encoder or has run out of
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* providers.
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*
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* <pre>{@code
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* public static Encoder getEncoder(String encodingName) {
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* for (CodecSet cp : codecSetLoader) {
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* Encoder enc = cp.getEncoder(encodingName);
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* if (enc != null)
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* return enc;
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* }
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* return null;
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* }}</pre>
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*
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* <p> A {@code getDecoder} method is defined similarly.
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*
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* <p> If the code creating and using the service loader is developed as
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* a module then its module descriptor will declare the usage with:
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* <pre>{@code uses com.example.CodecSet;}</pre>
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*
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* <p> Now suppose that {@code com.example.impl.StandardCodecs} is an
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* implementation of the {@code CodecSet} service and developed as a module.
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* In that case then the module with the service provider module will declare
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* this in its module descriptor:
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* <pre>{@code provides com.example.CodecSet with com.example.impl.StandardCodecs;
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* }</pre>
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*
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* <p> On the other hand, suppose {@code com.example.impl.StandardCodecs} is
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* packaged in a JAR file for the class path then the JAR file will contain a
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* file named:
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* <pre>{@code META-INF/services/com.example.CodecSet}</pre>
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* that contains the single line:
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* <pre>{@code com.example.impl.StandardCodecs # Standard codecs}</pre>
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*
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* <p><span style="font-weight: bold; padding-right: 1em">Usage Note</span> If
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* the class path of a class loader that is used for provider loading includes
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* remote network URLs then those URLs will be dereferenced in the process of
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* searching for provider-configuration files.
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*
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* <p> This activity is normal, although it may cause puzzling entries to be
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* created in web-server logs. If a web server is not configured correctly,
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* however, then this activity may cause the provider-loading algorithm to fail
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* spuriously.
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*
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* <p> A web server should return an HTTP 404 (Not Found) response when a
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* requested resource does not exist. Sometimes, however, web servers are
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* erroneously configured to return an HTTP 200 (OK) response along with a
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* helpful HTML error page in such cases. This will cause a {@link
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* ServiceConfigurationError} to be thrown when this class attempts to parse
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* the HTML page as a provider-configuration file. The best solution to this
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* problem is to fix the misconfigured web server to return the correct
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* response code (HTTP 404) along with the HTML error page.
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*
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* @param <S>
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* The type of the service to be loaded by this loader
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*
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* @author Mark Reinhold
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* @since 1.6
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*/
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public final class ServiceLoader<S>
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implements Iterable<S>
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{
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// The class or interface representing the service being loaded
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private final Class<S> service;
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// The class of the service type
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private final String serviceName;
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// The module Layer used to locate providers; null when locating
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// providers using a class loader
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private final Layer layer;
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// The class loader used to locate, load, and instantiate providers;
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// null when locating provider using a module Layer
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private final ClassLoader loader;
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// The access control context taken when the ServiceLoader is created
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private final AccessControlContext acc;
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// The lazy-lookup iterator for iterator operations
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private Iterator<Provider<S>> lookupIterator1;
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private final List<S> instantiatedProviders = new ArrayList<>();
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// The lazy-lookup iterator for stream operations
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private Iterator<Provider<S>> lookupIterator2;
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private final List<Provider<S>> loadedProviders = new ArrayList<>();
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private boolean loadedAllProviders; // true when all providers loaded
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// Incremented when reload is called
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private int reloadCount;
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private static JavaLangAccess LANG_ACCESS;
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private static JavaLangReflectModuleAccess JLRM_ACCESS;
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static {
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LANG_ACCESS = SharedSecrets.getJavaLangAccess();
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JLRM_ACCESS = SharedSecrets.getJavaLangReflectModuleAccess();
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}
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/**
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* Represents a service provider located by {@code ServiceLoader}.
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*
|
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* <p> When using a loader's {@link ServiceLoader#stream() stream()} method
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* then the elements are of type {@code Provider}. This allows processing
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* to select or filter on the provider class without instantiating the
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* provider. </p>
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*
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* @param <S> The service type
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* @since 9
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*/
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public static interface Provider<S> extends Supplier<S> {
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/**
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* Returns the provider type. There is no guarantee that this type is
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* accessible or that it has a public no-args constructor. The {@link
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* #get() get()} method should be used to obtain the provider instance.
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*
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* <p> When a module declares that the provider class is created by a
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* provider factory then this method returns the return type of its
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* public static "{@code provider()}" method.
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*
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* @return The provider type
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*/
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Class<? extends S> type();
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/**
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* Returns an instance of the provider.
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*
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* @return An instance of the provider.
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*
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* @throws ServiceConfigurationError
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* If the service provider cannot be instantiated, or in the
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* case of a provider factory, the public static
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* "{@code provider()}" method returns {@code null} or throws
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* an error or exception. The {@code ServiceConfigurationError}
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* will carry an appropriate cause where possible.
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*/
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@Override S get();
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}
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/**
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* Initializes a new instance of this class for locating service providers
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* in a module Layer.
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*
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* @throws ServiceConfigurationError
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* If {@code svc} is not accessible to {@code caller} or the caller
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* module does not use the service type.
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*/
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private ServiceLoader(Class<?> caller, Layer layer, Class<S> svc) {
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Objects.requireNonNull(caller);
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Objects.requireNonNull(layer);
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Objects.requireNonNull(svc);
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checkCaller(caller, svc);
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this.service = svc;
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this.serviceName = svc.getName();
|
|
this.layer = layer;
|
|
this.loader = null;
|
|
this.acc = (System.getSecurityManager() != null)
|
|
? AccessController.getContext()
|
|
: null;
|
|
}
|
|
|
|
/**
|
|
* Initializes a new instance of this class for locating service providers
|
|
* via a class loader.
|
|
*
|
|
* @throws ServiceConfigurationError
|
|
* If {@code svc} is not accessible to {@code caller} or the caller
|
|
* module does not use the service type.
|
|
*/
|
|
private ServiceLoader(Class<?> caller, Class<S> svc, ClassLoader cl) {
|
|
Objects.requireNonNull(svc);
|
|
|
|
if (VM.isBooted()) {
|
|
checkCaller(caller, svc);
|
|
if (cl == null) {
|
|
cl = ClassLoader.getSystemClassLoader();
|
|
}
|
|
} else {
|
|
|
|
// if we get here then it means that ServiceLoader is being used
|
|
// before the VM initialization has completed. At this point then
|
|
// only code in the java.base should be executing.
|
|
Module callerModule = caller.getModule();
|
|
Module base = Object.class.getModule();
|
|
Module svcModule = svc.getModule();
|
|
if (callerModule != base || svcModule != base) {
|
|
fail(svc, "not accessible to " + callerModule + " during VM init");
|
|
}
|
|
|
|
// restricted to boot loader during startup
|
|
cl = null;
|
|
}
|
|
|
|
this.service = svc;
|
|
this.serviceName = svc.getName();
|
|
this.layer = null;
|
|
this.loader = cl;
|
|
this.acc = (System.getSecurityManager() != null)
|
|
? AccessController.getContext()
|
|
: null;
|
|
}
|
|
|
|
/**
|
|
* Initializes a new instance of this class for locating service providers
|
|
* via a class loader.
|
|
*
|
|
* @apiNote For use by ResourceBundle
|
|
*
|
|
* @throws ServiceConfigurationError
|
|
* If the caller module does not use the service type.
|
|
*/
|
|
private ServiceLoader(Module callerModule, Class<S> svc, ClassLoader cl) {
|
|
if (!callerModule.canUse(svc)) {
|
|
fail(svc, callerModule + " does not declare `uses`");
|
|
}
|
|
|
|
this.service = Objects.requireNonNull(svc);
|
|
this.serviceName = svc.getName();
|
|
this.layer = null;
|
|
this.loader = cl;
|
|
this.acc = (System.getSecurityManager() != null)
|
|
? AccessController.getContext()
|
|
: null;
|
|
}
|
|
|
|
/**
|
|
* Checks that the given service type is accessible to types in the given
|
|
* module, and check that the module declare that it uses the service type. ??
|
|
*/
|
|
private static void checkCaller(Class<?> caller, Class<?> svc) {
|
|
Module callerModule = caller.getModule();
|
|
|
|
// Check access to the service type
|
|
int mods = svc.getModifiers();
|
|
if (!Reflection.verifyMemberAccess(caller, svc, null, mods)) {
|
|
fail(svc, "service type not accessible to " + callerModule);
|
|
}
|
|
|
|
// If the caller is in a named module then it should "uses" the
|
|
// service type
|
|
if (!callerModule.canUse(svc)) {
|
|
fail(svc, callerModule + " does not declare `uses`");
|
|
}
|
|
}
|
|
|
|
private static void fail(Class<?> service, String msg, Throwable cause)
|
|
throws ServiceConfigurationError
|
|
{
|
|
throw new ServiceConfigurationError(service.getName() + ": " + msg,
|
|
cause);
|
|
}
|
|
|
|
private static void fail(Class<?> service, String msg)
|
|
throws ServiceConfigurationError
|
|
{
|
|
throw new ServiceConfigurationError(service.getName() + ": " + msg);
|
|
}
|
|
|
|
private static void fail(Class<?> service, URL u, int line, String msg)
|
|
throws ServiceConfigurationError
|
|
{
|
|
fail(service, u + ":" + line + ": " + msg);
|
|
}
|
|
|
|
/**
|
|
* Uses Class.forName to load a provider class in a module.
|
|
*
|
|
* @throws ServiceConfigurationError
|
|
* If the class cannot be loaded
|
|
*/
|
|
private Class<?> loadProviderInModule(Module module, String cn) {
|
|
Class<?> clazz = null;
|
|
if (acc == null) {
|
|
try {
|
|
clazz = Class.forName(module, cn);
|
|
} catch (LinkageError e) {
|
|
fail(service, "Unable to load " + cn, e);
|
|
}
|
|
} else {
|
|
PrivilegedExceptionAction<Class<?>> pa = () -> Class.forName(module, cn);
|
|
try {
|
|
clazz = AccessController.doPrivileged(pa);
|
|
} catch (PrivilegedActionException pae) {
|
|
Throwable x = pae.getCause();
|
|
fail(service, "Unable to load " + cn, x);
|
|
return null;
|
|
}
|
|
}
|
|
if (clazz == null)
|
|
fail(service, "Provider " + cn + " not found");
|
|
return clazz;
|
|
}
|
|
|
|
/**
|
|
* A Provider implementation that supports invoking, with reduced
|
|
* permissions, the static factory to obtain the provider or the
|
|
* provider's no-arg constructor.
|
|
*/
|
|
private final static class ProviderImpl<S> implements Provider<S> {
|
|
final Class<S> service;
|
|
final AccessControlContext acc;
|
|
|
|
final Method factoryMethod; // factory method or null
|
|
final Class<? extends S> type;
|
|
final Constructor<? extends S> ctor; // public no-args constructor or null
|
|
|
|
/**
|
|
* Creates a Provider.
|
|
*
|
|
* @param service
|
|
* The service type
|
|
* @param clazz
|
|
* The provider (or provider factory) class
|
|
* @param acc
|
|
* The access control context when running with security manager
|
|
*
|
|
* @throws ServiceConfigurationError
|
|
* If the class is not public; If the class defines a public
|
|
* static provider() method with a return type that is assignable
|
|
* to the service type or the class is not a provider class with
|
|
* a public no-args constructor.
|
|
*/
|
|
@SuppressWarnings("unchecked")
|
|
ProviderImpl(Class<?> service, Class<?> clazz, AccessControlContext acc) {
|
|
this.service = (Class<S>) service;
|
|
this.acc = acc;
|
|
|
|
int mods = clazz.getModifiers();
|
|
if (!Modifier.isPublic(mods)) {
|
|
fail(service, clazz + " is not public");
|
|
}
|
|
|
|
// if the class is in an explicit module then see if it is
|
|
// a provider factory class
|
|
Method factoryMethod = null;
|
|
if (inExplicitModule(clazz)) {
|
|
factoryMethod = findStaticProviderMethod(clazz);
|
|
if (factoryMethod != null) {
|
|
Class<?> returnType = factoryMethod.getReturnType();
|
|
if (!service.isAssignableFrom(returnType)) {
|
|
fail(service, factoryMethod + " return type not a subtype");
|
|
}
|
|
}
|
|
}
|
|
this.factoryMethod = factoryMethod;
|
|
|
|
if (factoryMethod == null) {
|
|
// no factory method so must have a public no-args constructor
|
|
if (!service.isAssignableFrom(clazz)) {
|
|
fail(service, clazz.getName() + " not a subtype");
|
|
}
|
|
this.type = (Class<? extends S>) clazz;
|
|
this.ctor = (Constructor<? extends S>) getConstructor(clazz);
|
|
} else {
|
|
this.type = (Class<? extends S>) factoryMethod.getReturnType();
|
|
this.ctor = null;
|
|
}
|
|
}
|
|
|
|
@Override
|
|
public Class<? extends S> type() {
|
|
return type;
|
|
}
|
|
|
|
@Override
|
|
public S get() {
|
|
if (factoryMethod != null) {
|
|
return invokeFactoryMethod();
|
|
} else {
|
|
return newInstance();
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Returns {@code true} if the provider is in an explicit module
|
|
*/
|
|
private boolean inExplicitModule(Class<?> clazz) {
|
|
Module module = clazz.getModule();
|
|
return module.isNamed() && !module.getDescriptor().isAutomatic();
|
|
}
|
|
|
|
/**
|
|
* Returns the public static provider method if found.
|
|
*
|
|
* @throws ServiceConfigurationError if there is an error finding the
|
|
* provider method
|
|
*/
|
|
private Method findStaticProviderMethod(Class<?> clazz) {
|
|
Method method = null;
|
|
try {
|
|
method = LANG_ACCESS.getMethodOrNull(clazz, "provider");
|
|
} catch (Throwable x) {
|
|
fail(service, "Unable to get public provider() method", x);
|
|
}
|
|
if (method != null) {
|
|
int mods = method.getModifiers();
|
|
if (Modifier.isStatic(mods)) {
|
|
assert Modifier.isPublic(mods);
|
|
Method m = method;
|
|
PrivilegedAction<Void> pa = () -> {
|
|
m.setAccessible(true);
|
|
return null;
|
|
};
|
|
AccessController.doPrivileged(pa);
|
|
return method;
|
|
}
|
|
}
|
|
return null;
|
|
}
|
|
|
|
/**
|
|
* Returns the public no-arg constructor of a class.
|
|
*
|
|
* @throws ServiceConfigurationError if the class does not have
|
|
* public no-arg constructor
|
|
*/
|
|
private Constructor<?> getConstructor(Class<?> clazz) {
|
|
PrivilegedExceptionAction<Constructor<?>> pa
|
|
= new PrivilegedExceptionAction<>() {
|
|
@Override
|
|
public Constructor<?> run() throws Exception {
|
|
Constructor<?> ctor = clazz.getConstructor();
|
|
if (inExplicitModule(clazz))
|
|
ctor.setAccessible(true);
|
|
return ctor;
|
|
}
|
|
};
|
|
Constructor<?> ctor = null;
|
|
try {
|
|
ctor = AccessController.doPrivileged(pa);
|
|
} catch (Throwable x) {
|
|
if (x instanceof PrivilegedActionException)
|
|
x = x.getCause();
|
|
String cn = clazz.getName();
|
|
fail(service, cn + " Unable to get public no-arg constructor", x);
|
|
}
|
|
return ctor;
|
|
}
|
|
|
|
/**
|
|
* Invokes the provider's "provider" method to instantiate a provider.
|
|
* When running with a security manager then the method runs with
|
|
* permissions that are restricted by the security context of whatever
|
|
* created this loader.
|
|
*/
|
|
private S invokeFactoryMethod() {
|
|
Object result = null;
|
|
Throwable exc = null;
|
|
if (acc == null) {
|
|
try {
|
|
result = factoryMethod.invoke(null);
|
|
} catch (Throwable x) {
|
|
exc = x;
|
|
}
|
|
} else {
|
|
PrivilegedExceptionAction<?> pa = new PrivilegedExceptionAction<>() {
|
|
@Override
|
|
public Object run() throws Exception {
|
|
return factoryMethod.invoke(null);
|
|
}
|
|
};
|
|
// invoke factory method with permissions restricted by acc
|
|
try {
|
|
result = AccessController.doPrivileged(pa, acc);
|
|
} catch (PrivilegedActionException pae) {
|
|
exc = pae.getCause();
|
|
}
|
|
}
|
|
if (exc != null) {
|
|
if (exc instanceof InvocationTargetException)
|
|
exc = exc.getCause();
|
|
fail(service, factoryMethod + " failed", exc);
|
|
}
|
|
if (result == null) {
|
|
fail(service, factoryMethod + " returned null");
|
|
}
|
|
@SuppressWarnings("unchecked")
|
|
S p = (S) result;
|
|
return p;
|
|
}
|
|
|
|
/**
|
|
* Invokes Constructor::newInstance to instantiate a provider. When running
|
|
* with a security manager then the constructor runs with permissions that
|
|
* are restricted by the security context of whatever created this loader.
|
|
*/
|
|
private S newInstance() {
|
|
S p = null;
|
|
Throwable exc = null;
|
|
if (acc == null) {
|
|
try {
|
|
p = ctor.newInstance();
|
|
} catch (Throwable x) {
|
|
exc = x;
|
|
}
|
|
} else {
|
|
PrivilegedExceptionAction<S> pa = new PrivilegedExceptionAction<>() {
|
|
@Override
|
|
public S run() throws Exception {
|
|
return ctor.newInstance();
|
|
}
|
|
};
|
|
// invoke constructor with permissions restricted by acc
|
|
try {
|
|
p = AccessController.doPrivileged(pa, acc);
|
|
} catch (PrivilegedActionException pae) {
|
|
exc = pae.getCause();
|
|
}
|
|
}
|
|
if (exc != null) {
|
|
if (exc instanceof InvocationTargetException)
|
|
exc = exc.getCause();
|
|
String cn = ctor.getDeclaringClass().getName();
|
|
fail(service,
|
|
"Provider " + cn + " could not be instantiated", exc);
|
|
}
|
|
return p;
|
|
}
|
|
|
|
// For now, equals/hashCode uses the access control context to ensure
|
|
// that two Providers created with different contexts are not equal
|
|
// when running with a security manager.
|
|
|
|
@Override
|
|
public int hashCode() {
|
|
return Objects.hash(type, acc);
|
|
}
|
|
|
|
@Override
|
|
public boolean equals(Object ob) {
|
|
if (!(ob instanceof ProviderImpl))
|
|
return false;
|
|
@SuppressWarnings("unchecked")
|
|
ProviderImpl<?> that = (ProviderImpl<?>)ob;
|
|
return this.type == that.type
|
|
&& Objects.equals(this.acc, that.acc);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Implements lazy service provider lookup of service providers that
|
|
* are provided by modules in a module Layer (or parent layers)
|
|
*/
|
|
private final class LayerLookupIterator<T>
|
|
implements Iterator<Provider<T>>
|
|
{
|
|
Deque<Layer> stack = new ArrayDeque<>();
|
|
Set<Layer> visited = new HashSet<>();
|
|
Iterator<ServiceProvider> iterator;
|
|
ServiceProvider next; // next provider to load
|
|
|
|
LayerLookupIterator() {
|
|
visited.add(layer);
|
|
stack.push(layer);
|
|
}
|
|
|
|
private Iterator<ServiceProvider> providers(Layer layer) {
|
|
ServicesCatalog catalog = JLRM_ACCESS.getServicesCatalog(layer);
|
|
return catalog.findServices(serviceName).iterator();
|
|
}
|
|
|
|
@Override
|
|
public boolean hasNext() {
|
|
// already have the next provider cached
|
|
if (next != null)
|
|
return true;
|
|
|
|
while (true) {
|
|
|
|
// next provider (or provider factory)
|
|
if (iterator != null && iterator.hasNext()) {
|
|
next = iterator.next();
|
|
return true;
|
|
}
|
|
|
|
// next layer (DFS order)
|
|
if (stack.isEmpty())
|
|
return false;
|
|
|
|
Layer layer = stack.pop();
|
|
List<Layer> parents = layer.parents();
|
|
for (int i = parents.size() - 1; i >= 0; i--) {
|
|
Layer parent = parents.get(i);
|
|
if (!visited.contains(parent)) {
|
|
visited.add(parent);
|
|
stack.push(parent);
|
|
}
|
|
}
|
|
iterator = providers(layer);
|
|
}
|
|
}
|
|
|
|
@Override
|
|
public Provider<T> next() {
|
|
if (!hasNext())
|
|
throw new NoSuchElementException();
|
|
|
|
// take next provider
|
|
ServiceProvider provider = next;
|
|
next = null;
|
|
|
|
// attempt to load provider
|
|
Module module = provider.module();
|
|
String cn = provider.providerName();
|
|
Class<?> clazz = loadProviderInModule(module, cn);
|
|
return new ProviderImpl<T>(service, clazz, acc);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Implements lazy service provider lookup of service providers that
|
|
* are provided by modules defined to a class loader or to modules in
|
|
* layers with a module defined to the class loader.
|
|
*/
|
|
private final class ModuleServicesLookupIterator<T>
|
|
implements Iterator<Provider<T>>
|
|
{
|
|
ClassLoader currentLoader;
|
|
Iterator<ServiceProvider> iterator;
|
|
ServiceProvider next; // next provider to load
|
|
|
|
ModuleServicesLookupIterator() {
|
|
this.currentLoader = loader;
|
|
this.iterator = iteratorFor(loader);
|
|
}
|
|
|
|
/**
|
|
* Returns iterator to iterate over the implementations of {@code
|
|
* service} in the given layer.
|
|
*/
|
|
private List<ServiceProvider> providers(Layer layer) {
|
|
ServicesCatalog catalog = JLRM_ACCESS.getServicesCatalog(layer);
|
|
return catalog.findServices(serviceName);
|
|
}
|
|
|
|
/**
|
|
* Returns an iterator to iterate over the implementations of {@code
|
|
* service} in modules defined to the given class loader or in custom
|
|
* layers with a module defined to this class loader.
|
|
*/
|
|
private Iterator<ServiceProvider> iteratorFor(ClassLoader loader) {
|
|
|
|
// modules defined to this class loader
|
|
ServicesCatalog catalog;
|
|
if (loader == null) {
|
|
catalog = BootLoader.getServicesCatalog();
|
|
} else {
|
|
catalog = ServicesCatalog.getServicesCatalogOrNull(loader);
|
|
}
|
|
Stream<ServiceProvider> stream1;
|
|
if (catalog == null) {
|
|
stream1 = Stream.empty();
|
|
} else {
|
|
stream1 = catalog.findServices(serviceName).stream();
|
|
}
|
|
|
|
// modules in custom layers that define modules to the class loader
|
|
Stream<ServiceProvider> stream2;
|
|
if (loader == null) {
|
|
stream2 = Stream.empty();
|
|
} else {
|
|
Layer bootLayer = Layer.boot();
|
|
stream2 = JLRM_ACCESS.layers(loader)
|
|
.filter(l -> (l != bootLayer))
|
|
.map(l -> providers(l))
|
|
.flatMap(List::stream);
|
|
}
|
|
|
|
return Stream.concat(stream1, stream2).iterator();
|
|
}
|
|
|
|
@Override
|
|
public boolean hasNext() {
|
|
// already have the next provider cached
|
|
if (next != null)
|
|
return true;
|
|
|
|
while (true) {
|
|
if (iterator.hasNext()) {
|
|
next = iterator.next();
|
|
return true;
|
|
}
|
|
|
|
// move to the next class loader if possible
|
|
if (currentLoader == null) {
|
|
return false;
|
|
} else {
|
|
currentLoader = currentLoader.getParent();
|
|
iterator = iteratorFor(currentLoader);
|
|
}
|
|
}
|
|
}
|
|
|
|
@Override
|
|
public Provider<T> next() {
|
|
if (!hasNext())
|
|
throw new NoSuchElementException();
|
|
|
|
// take next provider
|
|
ServiceProvider provider = next;
|
|
next = null;
|
|
|
|
// attempt to load provider
|
|
Module module = provider.module();
|
|
String cn = provider.providerName();
|
|
Class<?> clazz = loadProviderInModule(module, cn);
|
|
return new ProviderImpl<T>(service, clazz, acc);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Implements lazy service provider lookup where the service providers are
|
|
* configured via service configuration files. Service providers in named
|
|
* modules are silently ignored by this lookup iterator.
|
|
*/
|
|
private final class LazyClassPathLookupIterator<T>
|
|
implements Iterator<Provider<T>>
|
|
{
|
|
static final String PREFIX = "META-INF/services/";
|
|
|
|
Enumeration<URL> configs;
|
|
Iterator<String> pending;
|
|
Class<?> nextClass;
|
|
String nextErrorMessage; // when hasNext fails with CNFE
|
|
|
|
LazyClassPathLookupIterator() { }
|
|
|
|
/**
|
|
* Parse a single line from the given configuration file, adding the
|
|
* name on the line to the names list.
|
|
*/
|
|
private int parseLine(URL u, BufferedReader r, int lc, Set<String> names)
|
|
throws IOException
|
|
{
|
|
String ln = r.readLine();
|
|
if (ln == null) {
|
|
return -1;
|
|
}
|
|
int ci = ln.indexOf('#');
|
|
if (ci >= 0) ln = ln.substring(0, ci);
|
|
ln = ln.trim();
|
|
int n = ln.length();
|
|
if (n != 0) {
|
|
if ((ln.indexOf(' ') >= 0) || (ln.indexOf('\t') >= 0))
|
|
fail(service, u, lc, "Illegal configuration-file syntax");
|
|
int cp = ln.codePointAt(0);
|
|
if (!Character.isJavaIdentifierStart(cp))
|
|
fail(service, u, lc, "Illegal provider-class name: " + ln);
|
|
int start = Character.charCount(cp);
|
|
for (int i = start; i < n; i += Character.charCount(cp)) {
|
|
cp = ln.codePointAt(i);
|
|
if (!Character.isJavaIdentifierPart(cp) && (cp != '.'))
|
|
fail(service, u, lc, "Illegal provider-class name: " + ln);
|
|
}
|
|
names.add(ln);
|
|
}
|
|
return lc + 1;
|
|
}
|
|
|
|
/**
|
|
* Parse the content of the given URL as a provider-configuration file.
|
|
*/
|
|
private Iterator<String> parse(URL u) {
|
|
Set<String> names = new LinkedHashSet<>(); // preserve insertion order
|
|
try {
|
|
URLConnection uc = u.openConnection();
|
|
uc.setUseCaches(false);
|
|
try (InputStream in = uc.getInputStream();
|
|
BufferedReader r
|
|
= new BufferedReader(new InputStreamReader(in, "utf-8")))
|
|
{
|
|
int lc = 1;
|
|
while ((lc = parseLine(u, r, lc, names)) >= 0);
|
|
}
|
|
} catch (IOException x) {
|
|
fail(service, "Error accessing configuration file", x);
|
|
}
|
|
return names.iterator();
|
|
}
|
|
|
|
private boolean hasNextService() {
|
|
if (nextClass != null || nextErrorMessage != null) {
|
|
return true;
|
|
}
|
|
|
|
Class<?> clazz = null;
|
|
do {
|
|
if (configs == null) {
|
|
try {
|
|
String fullName = PREFIX + service.getName();
|
|
if (loader == null)
|
|
configs = ClassLoader.getSystemResources(fullName);
|
|
else
|
|
configs = loader.getResources(fullName);
|
|
} catch (IOException x) {
|
|
fail(service, "Error locating configuration files", x);
|
|
}
|
|
}
|
|
while ((pending == null) || !pending.hasNext()) {
|
|
if (!configs.hasMoreElements()) {
|
|
return false;
|
|
}
|
|
pending = parse(configs.nextElement());
|
|
}
|
|
String cn = pending.next();
|
|
try {
|
|
clazz = Class.forName(cn, false, loader);
|
|
} catch (ClassNotFoundException x) {
|
|
// don't throw SCE here to long standing behavior
|
|
nextErrorMessage = "Provider " + cn + " not found";
|
|
return true;
|
|
}
|
|
|
|
} while (clazz.getModule().isNamed()); // ignore if in named module
|
|
|
|
nextClass = clazz;
|
|
return true;
|
|
}
|
|
|
|
private Provider<T> nextService() {
|
|
if (!hasNextService())
|
|
throw new NoSuchElementException();
|
|
|
|
// throw any SCE with error recorded by hasNext
|
|
if (nextErrorMessage != null) {
|
|
String msg = nextErrorMessage;
|
|
nextErrorMessage = null;
|
|
fail(service, msg);
|
|
}
|
|
|
|
// return next provider
|
|
Class<?> clazz = nextClass;
|
|
nextClass = null;
|
|
return new ProviderImpl<T>(service, clazz, acc);
|
|
}
|
|
|
|
@Override
|
|
public boolean hasNext() {
|
|
if (acc == null) {
|
|
return hasNextService();
|
|
} else {
|
|
PrivilegedAction<Boolean> action = new PrivilegedAction<>() {
|
|
public Boolean run() { return hasNextService(); }
|
|
};
|
|
return AccessController.doPrivileged(action, acc);
|
|
}
|
|
}
|
|
|
|
@Override
|
|
public Provider<T> next() {
|
|
if (acc == null) {
|
|
return nextService();
|
|
} else {
|
|
PrivilegedAction<Provider<T>> action = new PrivilegedAction<>() {
|
|
public Provider<T> run() { return nextService(); }
|
|
};
|
|
return AccessController.doPrivileged(action, acc);
|
|
}
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Returns a new lookup iterator.
|
|
*/
|
|
private Iterator<Provider<S>> newLookupIterator() {
|
|
assert layer == null || loader == null;
|
|
if (layer != null) {
|
|
return new LayerLookupIterator<>();
|
|
} else {
|
|
Iterator<Provider<S>> first = new ModuleServicesLookupIterator<>();
|
|
Iterator<Provider<S>> second = new LazyClassPathLookupIterator<>();
|
|
return new Iterator<Provider<S>>() {
|
|
@Override
|
|
public boolean hasNext() {
|
|
return (first.hasNext() || second.hasNext());
|
|
}
|
|
@Override
|
|
public Provider<S> next() {
|
|
if (first.hasNext()) {
|
|
return first.next();
|
|
} else if (second.hasNext()) {
|
|
return second.next();
|
|
} else {
|
|
throw new NoSuchElementException();
|
|
}
|
|
}
|
|
};
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Lazily load and instantiate the available providers of this loader's
|
|
* service.
|
|
*
|
|
* <p> The iterator returned by this method first yields all of the
|
|
* elements of the provider cache, in the order that they were loaded.
|
|
* It then lazily loads and instantiates any remaining providers,
|
|
* adding each one to the cache in turn.
|
|
*
|
|
* <p> To achieve laziness the actual work of locating and instantiating
|
|
* providers must be done by the iterator itself. Its {@link
|
|
* java.util.Iterator#hasNext hasNext} and {@link java.util.Iterator#next
|
|
* next} methods can therefore throw a {@link ServiceConfigurationError}
|
|
* if a provider class cannot be loaded, doesn't have an appropriate static
|
|
* factory method or constructor, can't be assigned 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 {@link ServiceConfigurationError} when using a service iterator.
|
|
*
|
|
* <p> 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.
|
|
*
|
|
* <blockquote style="font-size: smaller; line-height: 1.2"><span
|
|
* style="padding-right: 1em; font-weight: bold">Design Note</span>
|
|
* 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.</blockquote>
|
|
*
|
|
* <p> If this loader's provider caches are cleared by invoking the {@link
|
|
* #reload() reload} method then existing iterators for this service
|
|
* loader should be discarded.
|
|
* The {@link java.util.Iterator#hasNext() hasNext} and {@link
|
|
* java.util.Iterator#next() next} methods of the iterator throw {@link
|
|
* java.util.ConcurrentModificationException ConcurrentModificationException}
|
|
* if used after the provider cache has been cleared.
|
|
*
|
|
* <p> The iterator returned by this method does not support removal.
|
|
* Invoking its {@link java.util.Iterator#remove() remove} method will
|
|
* cause an {@link UnsupportedOperationException} to be thrown.
|
|
*
|
|
* @return An iterator that lazily loads providers for this loader's
|
|
* service
|
|
*/
|
|
public Iterator<S> iterator() {
|
|
|
|
// create lookup iterator if needed
|
|
if (lookupIterator1 == null) {
|
|
lookupIterator1 = newLookupIterator();
|
|
}
|
|
|
|
return new Iterator<S>() {
|
|
|
|
// record reload count
|
|
final int expectedReloadCount = ServiceLoader.this.reloadCount;
|
|
|
|
// index into the cached providers list
|
|
int index;
|
|
|
|
/**
|
|
* Throws ConcurrentModificationException if the list of cached
|
|
* providers has been cleared by reload.
|
|
*/
|
|
private void checkReloadCount() {
|
|
if (ServiceLoader.this.reloadCount != expectedReloadCount)
|
|
throw new ConcurrentModificationException();
|
|
}
|
|
|
|
@Override
|
|
public boolean hasNext() {
|
|
checkReloadCount();
|
|
if (index < instantiatedProviders.size())
|
|
return true;
|
|
return lookupIterator1.hasNext();
|
|
}
|
|
|
|
@Override
|
|
public S next() {
|
|
checkReloadCount();
|
|
S next;
|
|
if (index < instantiatedProviders.size()) {
|
|
next = instantiatedProviders.get(index);
|
|
} else {
|
|
next = lookupIterator1.next().get();
|
|
instantiatedProviders.add(next);
|
|
}
|
|
index++;
|
|
return next;
|
|
}
|
|
|
|
};
|
|
}
|
|
|
|
/**
|
|
* Returns a stream that lazily loads the available providers of this
|
|
* loader's service. The stream elements are of type {@link Provider
|
|
* Provider}, the {@code Provider}'s {@link Provider#get() get} method
|
|
* must be invoked to get or instantiate the provider.
|
|
*
|
|
* <p> When processing the stream then providers that were previously
|
|
* loaded by stream operations are processed first, in load order. It then
|
|
* lazily loads any remaining providers. If a provider class cannot be
|
|
* loaded, can't be assigned to the service type, or some other error is
|
|
* thrown when locating the provider then it is wrapped with a {@code
|
|
* ServiceConfigurationError} and thrown by whatever method caused the
|
|
* provider to be loaded. </p>
|
|
*
|
|
* <p> If this loader's provider caches are cleared by invoking the {@link
|
|
* #reload() reload} method then existing streams for this service
|
|
* loader should be discarded. </p>
|
|
*
|
|
* <p> The following examples demonstrate usage. The first example
|
|
* creates a stream of providers, the second example is the same except
|
|
* that it sorts the providers by provider class name (and so locate all
|
|
* providers).
|
|
* <pre>{@code
|
|
* Stream<CodecSet> providers = ServiceLoader.load(CodecSet.class)
|
|
* .stream()
|
|
* .map(Provider::get);
|
|
*
|
|
* Stream<CodecSet> providers = ServiceLoader.load(CodecSet.class)
|
|
* .stream()
|
|
* .sorted(Comparator.comparing(p -> p.type().getName()))
|
|
* .map(Provider::get);
|
|
* }</pre>
|
|
*
|
|
* @return A stream that lazily loads providers for this loader's service
|
|
*
|
|
* @since 9
|
|
*/
|
|
public Stream<Provider<S>> stream() {
|
|
// use cached providers as the source when all providers loaded
|
|
if (loadedAllProviders) {
|
|
return loadedProviders.stream();
|
|
}
|
|
|
|
// create lookup iterator if needed
|
|
if (lookupIterator2 == null) {
|
|
lookupIterator2 = newLookupIterator();
|
|
}
|
|
|
|
// use lookup iterator and cached providers as source
|
|
Spliterator<Provider<S>> s = new ProviderSpliterator<>(lookupIterator2);
|
|
return StreamSupport.stream(s, false);
|
|
}
|
|
|
|
private class ProviderSpliterator<T> implements Spliterator<Provider<T>> {
|
|
final int expectedReloadCount = ServiceLoader.this.reloadCount;
|
|
final Iterator<Provider<T>> iterator;
|
|
int index;
|
|
|
|
ProviderSpliterator(Iterator<Provider<T>> iterator) {
|
|
this.iterator = iterator;
|
|
}
|
|
|
|
@Override
|
|
public Spliterator<Provider<T>> trySplit() {
|
|
return null;
|
|
}
|
|
|
|
@Override
|
|
@SuppressWarnings("unchecked")
|
|
public boolean tryAdvance(Consumer<? super Provider<T>> action) {
|
|
if (ServiceLoader.this.reloadCount != expectedReloadCount)
|
|
throw new ConcurrentModificationException();
|
|
Provider<T> next = null;
|
|
if (index < loadedProviders.size()) {
|
|
next = (Provider<T>) loadedProviders.get(index++);
|
|
} else if (iterator.hasNext()) {
|
|
next = iterator.next();
|
|
} else {
|
|
loadedAllProviders = true;
|
|
}
|
|
if (next != null) {
|
|
action.accept(next);
|
|
return true;
|
|
} else {
|
|
return false;
|
|
}
|
|
}
|
|
|
|
@Override
|
|
public int characteristics() {
|
|
// not IMMUTABLE as structural interference possible
|
|
// not NOTNULL so that the characteristics are a subset of the
|
|
// characteristics when all Providers have been located.
|
|
return Spliterator.ORDERED;
|
|
}
|
|
|
|
@Override
|
|
public long estimateSize() {
|
|
return Long.MAX_VALUE;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Creates a new service loader for the given service type, class
|
|
* loader, and caller.
|
|
*
|
|
* @param <S> the class of the service type
|
|
*
|
|
* @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 <tt>null</tt> if the system class
|
|
* loader (or, failing that, the bootstrap class loader) is to be
|
|
* used
|
|
*
|
|
* @param callerModule
|
|
* The caller's module for which a new service loader is created
|
|
*
|
|
* @return A new service loader
|
|
*/
|
|
static <S> ServiceLoader<S> load(Class<S> service,
|
|
ClassLoader loader,
|
|
Module callerModule)
|
|
{
|
|
return new ServiceLoader<>(callerModule, service, loader);
|
|
}
|
|
|
|
/**
|
|
* Creates a new service loader for the given service type and class
|
|
* loader.
|
|
*
|
|
* @param <S> the class of the service type
|
|
*
|
|
* @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 {@code null} if the system class
|
|
* loader (or, failing that, the bootstrap class loader) is to be
|
|
* used
|
|
*
|
|
* @return A new service loader
|
|
*
|
|
* @throws ServiceConfigurationError
|
|
* if the service type is not accessible to the caller or the
|
|
* caller is in an explicit module and its module descriptor does
|
|
* not declare that it uses {@code service}
|
|
*/
|
|
@CallerSensitive
|
|
public static <S> ServiceLoader<S> load(Class<S> service,
|
|
ClassLoader loader)
|
|
{
|
|
return new ServiceLoader<>(Reflection.getCallerClass(), service, loader);
|
|
}
|
|
|
|
/**
|
|
* Creates a new service loader for the given service type, using the
|
|
* current thread's {@linkplain java.lang.Thread#getContextClassLoader
|
|
* context class loader}.
|
|
*
|
|
* <p> An invocation of this convenience method of the form
|
|
* <pre>{@code
|
|
* ServiceLoader.load(service)
|
|
* }</pre>
|
|
*
|
|
* is equivalent to
|
|
*
|
|
* <pre>{@code
|
|
* ServiceLoader.load(service, Thread.currentThread().getContextClassLoader())
|
|
* }</pre>
|
|
*
|
|
* @apiNote Service loader objects obtained with this method should not be
|
|
* cached VM-wide. For example, different applications in the same VM may
|
|
* have different thread context class loaders. A lookup by one application
|
|
* may locate a service provider that is only visible via its thread
|
|
* context class loader and so is not suitable to be located by the other
|
|
* application. Memory leaks can also arise. A thread local may be suited
|
|
* to some applications.
|
|
*
|
|
* @param <S> the class of the service type
|
|
*
|
|
* @param service
|
|
* The interface or abstract class representing the service
|
|
*
|
|
* @return A new service loader
|
|
*
|
|
* @throws ServiceConfigurationError
|
|
* if the service type is not accessible to the caller or the
|
|
* caller is in an explicit module and its module descriptor does
|
|
* not declare that it uses {@code service}
|
|
*/
|
|
@CallerSensitive
|
|
public static <S> ServiceLoader<S> load(Class<S> service) {
|
|
ClassLoader cl = Thread.currentThread().getContextClassLoader();
|
|
return new ServiceLoader<>(Reflection.getCallerClass(), service, cl);
|
|
}
|
|
|
|
/**
|
|
* Creates a new service loader for the given service type, using the
|
|
* {@linkplain ClassLoader#getPlatformClassLoader() platform class loader}.
|
|
*
|
|
* <p> This convenience method is equivalent to: </p>
|
|
*
|
|
* <pre>{@code
|
|
* ServiceLoader.load(service, ClassLoader.getPlatformClassLoader())
|
|
* }</pre>
|
|
*
|
|
* <p> 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 module path or class path will be ignored.
|
|
*
|
|
* @param <S> the class of the service type
|
|
*
|
|
* @param service
|
|
* The interface or abstract class representing the service
|
|
*
|
|
* @return A new service loader
|
|
*
|
|
* @throws ServiceConfigurationError
|
|
* if the service type is not accessible to the caller or the
|
|
* caller is in an explicit module and its module descriptor does
|
|
* not declare that it uses {@code service}
|
|
*/
|
|
@CallerSensitive
|
|
public static <S> ServiceLoader<S> loadInstalled(Class<S> service) {
|
|
ClassLoader cl = ClassLoader.getPlatformClassLoader();
|
|
return new ServiceLoader<>(Reflection.getCallerClass(), service, cl);
|
|
}
|
|
|
|
/**
|
|
* Creates a new service loader for the given service type that loads
|
|
* service providers from modules in the given {@code Layer} and its
|
|
* ancestors.
|
|
*
|
|
* @apiNote Unlike the other load methods defined here, the service type
|
|
* is the second parameter. The reason for this is to avoid source
|
|
* compatibility issues for code that uses {@code load(S, null)}.
|
|
*
|
|
* @param <S> the class of the service type
|
|
*
|
|
* @param layer
|
|
* The module Layer
|
|
*
|
|
* @param service
|
|
* The interface or abstract class representing the service
|
|
*
|
|
* @return A new service loader
|
|
*
|
|
* @throws ServiceConfigurationError
|
|
* if the service type is not accessible to the caller or the
|
|
* caller is in an explicit module and its module descriptor does
|
|
* not declare that it uses {@code service}
|
|
*
|
|
* @since 9
|
|
*/
|
|
@CallerSensitive
|
|
public static <S> ServiceLoader<S> load(Layer layer, Class<S> service) {
|
|
return new ServiceLoader<>(Reflection.getCallerClass(), layer, service);
|
|
}
|
|
|
|
/**
|
|
* Load the first available provider of this loader's service. This
|
|
* convenience method is equivalent to invoking the {@link #iterator()
|
|
* iterator()} method and obtaining the first element. It therefore
|
|
* returns the first element from the provider cache if possible, it
|
|
* otherwise attempts to load and instantiate the first provider.
|
|
*
|
|
* <p> The following example loads the first available provider. If there
|
|
* are no providers deployed then it uses a default implementation.
|
|
* <pre>{@code
|
|
* CodecSet provider =
|
|
* ServiceLoader.load(CodecSet.class).findFirst().orElse(DEFAULT_CODECSET);
|
|
* }</pre>
|
|
* @return The first provider or empty {@code Optional} if no providers
|
|
* are located
|
|
*
|
|
* @throws ServiceConfigurationError
|
|
* If a provider class cannot be loaded, doesn't have the
|
|
* appropriate static factory method or constructor, can't be
|
|
* assigned to the service type, or if any other kind of exception
|
|
* or error is thrown when locating or instantiating the provider.
|
|
*
|
|
* @since 9
|
|
*/
|
|
public Optional<S> findFirst() {
|
|
Iterator<S> iterator = iterator();
|
|
if (iterator.hasNext()) {
|
|
return Optional.of(iterator.next());
|
|
} else {
|
|
return Optional.empty();
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Clear this loader's provider cache so that all providers will be
|
|
* reloaded.
|
|
*
|
|
* <p> After invoking this method, subsequent invocations of the {@link
|
|
* #iterator() iterator} or {@link #stream() stream} methods will lazily
|
|
* look up providers (and instantiate in the case of {@code iterator})
|
|
* from scratch, just as is done by a newly-created loader.
|
|
*
|
|
* <p> This method is intended for use in situations in which new providers
|
|
* can be installed into a running Java virtual machine.
|
|
*/
|
|
public void reload() {
|
|
lookupIterator1 = null;
|
|
instantiatedProviders.clear();
|
|
|
|
lookupIterator2 = null;
|
|
loadedProviders.clear();
|
|
loadedAllProviders = false;
|
|
|
|
// increment count to allow CME be thrown
|
|
reloadCount++;
|
|
}
|
|
|
|
/**
|
|
* Returns a string describing this service.
|
|
*
|
|
* @return A descriptive string
|
|
*/
|
|
public String toString() {
|
|
return "java.util.ServiceLoader[" + service.getName() + "]";
|
|
}
|
|
|
|
}
|