| /* |
| * Copyright (c) 2005, 2016, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| package java.util; |
| |
| import java.io.BufferedReader; |
| import java.io.IOException; |
| import java.io.InputStream; |
| import java.io.InputStreamReader; |
| import java.lang.reflect.Constructor; |
| import java.lang.reflect.InvocationTargetException; |
| import java.lang.reflect.Layer; |
| import java.lang.reflect.Method; |
| import java.lang.reflect.Modifier; |
| import java.lang.reflect.Module; |
| import java.net.URL; |
| import java.net.URLConnection; |
| import java.security.AccessControlContext; |
| import java.security.AccessController; |
| import java.security.PrivilegedAction; |
| import java.security.PrivilegedActionException; |
| import java.security.PrivilegedExceptionAction; |
| import java.util.function.Consumer; |
| import java.util.function.Supplier; |
| import java.util.stream.Stream; |
| import java.util.stream.StreamSupport; |
| |
| import jdk.internal.loader.BootLoader; |
| import jdk.internal.misc.JavaLangAccess; |
| import jdk.internal.misc.JavaLangReflectModuleAccess; |
| import jdk.internal.misc.SharedSecrets; |
| import jdk.internal.misc.VM; |
| import jdk.internal.module.ServicesCatalog; |
| import jdk.internal.module.ServicesCatalog.ServiceProvider; |
| import jdk.internal.reflect.CallerSensitive; |
| import jdk.internal.reflect.Reflection; |
| |
| |
| /** |
| * A simple service-provider loading facility. |
| * |
| * <p> A <i>service</i> is a well-known set of interfaces and (usually |
| * abstract) classes. A <i>service provider</i> is a specific implementation |
| * of a service. The classes in a provider typically implement the interfaces |
| * and subclass the classes defined in the service itself. |
| * Providers may be developed and deployed as modules and made available using |
| * the application module path. Providers may alternatively be packaged as JAR |
| * files and made available by adding them to the application class path. The |
| * advantage of developing a provider as a module is that the provider can be |
| * fully encapsulated to hide all details of its implementation. |
| * |
| * <p> For the purpose of loading, a service is represented by a single type, |
| * that is, a single interface or abstract class. (A concrete class can be |
| * used, but this is not recommended.) A provider of a given service contains |
| * one or more concrete classes that extend this <i>service type</i> with data |
| * and code specific to the provider. The <i>provider class</i> is typically |
| * not the entire provider itself but rather a proxy which contains enough |
| * information to decide whether the provider is able to satisfy a particular |
| * request together with code that can create the actual provider on demand. |
| * The details of provider classes tend to be highly service-specific; no |
| * single class or interface could possibly unify them, so no such type is |
| * defined here. |
| * |
| * <p> Providers deployed as explicit modules on the module path are |
| * instantiated by a <em>provider factory</em> or directly via the provider's |
| * constructor. In the module declaration then the class name specified in the |
| * <i>provides</i> clause is a provider factory if it is public and defines a |
| * public static no-args method named "{@code provider}". The return type of |
| * the method must be assignable to the <i>service</i> type. If the class is |
| * not a provider factory then it is public with a public zero-argument |
| * constructor. The requirement that the provider factory or provider class |
| * be public helps to document the intent that the provider will be |
| * instantiated by the service-provider loading facility. |
| * |
| * <p> As an example, suppose a module declares the following: |
| * |
| * <pre>{@code |
| * provides com.example.CodecSet with com.example.impl.StandardCodecs; |
| * provides com.example.CodecSet with com.example.impl.ExtendedCodecsFactory; |
| * }</pre> |
| * |
| * <p> where {@code com.example.CodecSet} is the service type, {@code |
| * com.example.impl.StandardCodecs} is a provider class that is public with a |
| * public no-args constructor, {@code com.example.impl.ExtendedCodecsFactory} |
| * is a public class that defines a public static no-args method named |
| * "{@code provider}" with a return type that is {@code CodecSet} or a subtype |
| * of. For this example then {@code StandardCodecs}'s no-arg constructor will |
| * be used to instantiate {@code StandardCodecs}. {@code ExtendedCodecsFactory} |
| * will be treated as a provider factory and {@code |
| * ExtendedCodecsFactory.provider()} will be invoked to obtain the provider. |
| * |
| * <p> Providers deployed on the class path or as {@link |
| * java.lang.module.ModuleDescriptor#isAutomatic automatic-modules} on the |
| * module path must have a public zero-argument constructor. |
| * |
| * <p> An application or library using this loading facility and developed |
| * and deployed as an explicit module must have an appropriate <i>uses</i> |
| * clause in its <i>module descriptor</i> to declare that the module uses |
| * implementations of the service. A corresponding requirement is that a |
| * provider deployed as a named module must have an appropriate |
| * <i>provides</i> clause in its module descriptor to declare that the module |
| * provides an implementation of the service. The <i>uses</i> and |
| * <i>provides</i> allow consumers of a service to be <i>linked</i> to modules |
| * containing providers of the service. |
| * |
| * <p> A service provider that is packaged as a JAR file for the class path is |
| * identified by placing a <i>provider-configuration file</i> in the resource |
| * directory <tt>META-INF/services</tt>. The file's name is the fully-qualified |
| * <a href="../lang/ClassLoader.html#name">binary name</a> of the service's |
| * type. The file contains a list of fully-qualified binary names of concrete |
| * provider classes, one per line. Space and tab characters surrounding each |
| * name, as well as blank lines, are ignored. The comment character is |
| * <tt>'#'</tt> (<tt>'\u0023'</tt>, |
| * <font style="font-size:smaller;">NUMBER SIGN</font>); on |
| * each line all characters following the first comment character are ignored. |
| * The file must be encoded in UTF-8. |
| * If a particular concrete provider class is named in more than one |
| * configuration file, or is named in the same configuration file more than |
| * once, then the duplicates are ignored. The configuration file naming a |
| * particular provider need not be in the same JAR file or other distribution |
| * unit as the provider itself. The provider must be visible from the same |
| * class loader that was initially queried to locate the configuration file; |
| * note that this is not necessarily the class loader from which the file was |
| * actually loaded. |
| * |
| * <p> Providers are located and instantiated lazily, that is, on demand. A |
| * service loader maintains a cache of the providers that have been loaded so |
| * far. Each invocation of the {@link #iterator iterator} method returns an |
| * iterator that first yields all of the elements cached from previous |
| * iteration, in instantiation order, and then lazily locates and instantiates |
| * any remaining providers, adding each one to the cache in turn. Similarly, |
| * each invocation of the {@link #stream stream} method returns a stream that |
| * first processes all providers loaded by previous stream operations, in load |
| * order, and then lazily locates any remaining providers. Caches are cleared |
| * via the {@link #reload reload} method. |
| * |
| * <h2> Locating providers </h2> |
| * |
| * <p> The {@code load} methods locate providers using a class loader or module |
| * {@link Layer layer}. When locating providers using a class loader then |
| * providers in both named and unnamed modules may be located. When locating |
| * providers using a module layer then only providers in named modules in |
| * the layer (or parent layers) are located. |
| * |
| * <p> When locating providers using a class loader then any providers in named |
| * modules defined to the class loader, or any class loader that is reachable |
| * via parent delegation, are located. Additionally, providers in module layers |
| * other than the {@link Layer#boot() boot} layer, where the module layer |
| * contains modules defined to the class loader, or any class loader reachable |
| * via parent delegation, are also located. For example, suppose there is a |
| * module layer where each module is defined to its own class loader (see {@link |
| * Layer#defineModulesWithManyLoaders defineModulesWithManyLoaders}). If the |
| * {@code load} method is invoked to locate providers using any of these class |
| * loaders for this layer then it will locate all of the providers in that |
| * layer, irrespective of their defining class loader. |
| * |
| * <p> In the case of unnamed modules then the service configuration files are |
| * located using the class loader's {@link ClassLoader#getResources(String) |
| * ClassLoader.getResources(String)} method. Any providers listed should be |
| * visible via the class loader specified to the {@code load} method. If a |
| * provider in a named module is listed then it is ignored - this is to avoid |
| * duplicates that would otherwise arise when a module has both a |
| * <i>provides</i> clause and a service configuration file in {@code |
| * META-INF/services} that lists the same provider. |
| * |
| * <h2> Ordering </h2> |
| * |
| * <p> Service loaders created to locate providers using a {@code ClassLoader} |
| * locate providers as follows: |
| * <ul> |
| * <li> Providers in named modules are located before providers on the |
| * class path (or more generally, unnamed modules). </li> |
| * |
| * <li> When locating providers in named modules then the service loader |
| * will locate providers in modules defined to the class loader, then its |
| * parent class loader, its parent parent, and so on to the bootstrap class |
| * loader. If a {@code ClassLoader}, or any class loader in the parent |
| * delegation chain, defines modules in a custom module {@link Layer} then |
| * all providers in that layer are located, irrespective of their class |
| * loader. The ordering of modules defined to the same class loader, or the |
| * ordering of modules in a layer, is not defined. </li> |
| * |
| * <li> If a named module declares more than one provider then the providers |
| * are located in the order that they appear in the {@code provides} table of |
| * the {@code Module} class file attribute ({@code module-info.class}). </li> |
| * |
| * <li> When locating providers in unnamed modules then the ordering is |
| * based on the order that the class loader's {@link |
| * ClassLoader#getResources(String) ClassLoader.getResources(String)} |
| * method finds the service configuration files. </li> |
| * </ul> |
| * |
| * <p> Service loaders created to locate providers in a module {@link Layer} |
| * will first locate providers in the layer, before locating providers in |
| * parent layers. Traversal of parent layers is depth-first with each layer |
| * visited at most once. For example, suppose L0 is the boot layer, L1 and |
| * L2 are custom layers with L0 as their parent. Now suppose that L3 is |
| * created with L1 and L2 as the parents (in that order). Using a service |
| * loader to locate providers with L3 as the content will locate providers |
| * in the following order: L3, L1, L0, L2. The ordering of modules in a layer |
| * is not defined. |
| * |
| * <h2> Selection and filtering </h2> |
| * |
| * <p> Selecting a provider or filtering providers will usually involve invoking |
| * a provider method. Where selection or filtering based on the provider class is |
| * needed then it can be done using a {@link #stream() stream}. For example, the |
| * following collects the providers that have a specific annotation: |
| * <pre>{@code |
| * Set<CodecSet> providers = ServiceLoader.load(CodecSet.class) |
| * .stream() |
| * .filter(p -> p.type().isAnnotationPresent(Managed.class)) |
| * .map(Provider::get) |
| * .collect(Collectors.toSet()); |
| * }</pre> |
| * |
| * <h2> Security </h2> |
| * |
| * <p> Service loaders always execute in the security context of the caller |
| * of the iterator or stream methods and may also be restricted by the security |
| * context of the caller that created the service loader. |
| * Trusted system code should typically invoke the methods in this class, and |
| * the methods of the iterators which they return, from within a privileged |
| * security context. |
| * |
| * <h2> Concurrency </h2> |
| * |
| * <p> Instances of this class are not safe for use by multiple concurrent |
| * threads. |
| * |
| * <h2> Null handling </h2> |
| * |
| * <p> Unless otherwise specified, passing a {@code null} argument to any |
| * method in this class will cause a {@link NullPointerException} to be thrown. |
| * |
| * <h2> Example </h2> |
| * <p> Suppose we have a service type <tt>com.example.CodecSet</tt> which is |
| * intended to represent sets of encoder/decoder pairs for some protocol. In |
| * this case it is an abstract class with two abstract methods: |
| * |
| * <blockquote><pre> |
| * public abstract Encoder getEncoder(String encodingName); |
| * public abstract Decoder getDecoder(String encodingName);</pre></blockquote> |
| * |
| * Each method returns an appropriate object or <tt>null</tt> if the provider |
| * does not support the given encoding. Typical providers support more than |
| * one encoding. |
| * |
| * <p> The <tt>CodecSet</tt> class creates and saves a single service instance |
| * at initialization: |
| * |
| * <pre>{@code |
| * private static ServiceLoader<CodecSet> codecSetLoader |
| * = ServiceLoader.load(CodecSet.class); |
| * }</pre> |
| * |
| * <p> To locate an encoder for a given encoding name it defines a static |
| * factory method which iterates through the known and available providers, |
| * returning only when it has located a suitable encoder or has run out of |
| * providers. |
| * |
| * <pre>{@code |
| * public static Encoder getEncoder(String encodingName) { |
| * for (CodecSet cp : codecSetLoader) { |
| * Encoder enc = cp.getEncoder(encodingName); |
| * if (enc != null) |
| * return enc; |
| * } |
| * return null; |
| * }}</pre> |
| * |
| * <p> A {@code getDecoder} method is defined similarly. |
| * |
| * <p> If the code creating and using the service loader is developed as |
| * a module then its module descriptor will declare the usage with: |
| * <pre>{@code uses com.example.CodecSet;}</pre> |
| * |
| * <p> Now suppose that {@code com.example.impl.StandardCodecs} is an |
| * implementation of the {@code CodecSet} service and developed as a module. |
| * In that case then the module with the service provider module will declare |
| * this in its module descriptor: |
| * <pre>{@code provides com.example.CodecSet with com.example.impl.StandardCodecs; |
| * }</pre> |
| * |
| * <p> On the other hand, suppose {@code com.example.impl.StandardCodecs} is |
| * packaged in a JAR file for the class path then the JAR file will contain a |
| * file named: |
| * <pre>{@code META-INF/services/com.example.CodecSet}</pre> |
| * that contains the single line: |
| * <pre>{@code com.example.impl.StandardCodecs # Standard codecs}</pre> |
| * |
| * <p><span style="font-weight: bold; padding-right: 1em">Usage Note</span> If |
| * the class path of a class loader that is used for provider loading includes |
| * remote network URLs then those URLs will be dereferenced in the process of |
| * searching for provider-configuration files. |
| * |
| * <p> This activity is normal, although it may cause puzzling entries to be |
| * created in web-server logs. If a web server is not configured correctly, |
| * however, then this activity may cause the provider-loading algorithm to fail |
| * spuriously. |
| * |
| * <p> A web server should return an HTTP 404 (Not Found) response when a |
| * requested resource does not exist. Sometimes, however, web servers are |
| * erroneously configured to return an HTTP 200 (OK) response along with a |
| * helpful HTML error page in such cases. This will cause a {@link |
| * ServiceConfigurationError} to be thrown when this class attempts to parse |
| * the HTML page as a provider-configuration file. The best solution to this |
| * problem is to fix the misconfigured web server to return the correct |
| * response code (HTTP 404) along with the HTML error page. |
| * |
| * @param <S> |
| * The type of the service to be loaded by this loader |
| * |
| * @author Mark Reinhold |
| * @since 1.6 |
| */ |
| |
| public final class ServiceLoader<S> |
| implements Iterable<S> |
| { |
| // The class or interface representing the service being loaded |
| private final Class<S> service; |
| |
| // The class of the service type |
| private final String serviceName; |
| |
| // The module Layer used to locate providers; null when locating |
| // providers using a class loader |
| private final Layer layer; |
| |
| // The class loader used to locate, load, and instantiate providers; |
| // null when locating provider using a module Layer |
| private final ClassLoader loader; |
| |
| // The access control context taken when the ServiceLoader is created |
| private final AccessControlContext acc; |
| |
| // The lazy-lookup iterator for iterator operations |
| private Iterator<Provider<S>> lookupIterator1; |
| private final List<S> instantiatedProviders = new ArrayList<>(); |
| |
| // The lazy-lookup iterator for stream operations |
| private Iterator<Provider<S>> lookupIterator2; |
| private final List<Provider<S>> loadedProviders = new ArrayList<>(); |
| private boolean loadedAllProviders; // true when all providers loaded |
| |
| // Incremented when reload is called |
| private int reloadCount; |
| |
| private static JavaLangAccess LANG_ACCESS; |
| private static JavaLangReflectModuleAccess JLRM_ACCESS; |
| static { |
| LANG_ACCESS = SharedSecrets.getJavaLangAccess(); |
| JLRM_ACCESS = SharedSecrets.getJavaLangReflectModuleAccess(); |
| } |
| |
| /** |
| * Represents a service provider located by {@code ServiceLoader}. |
| * |
| * <p> When using a loader's {@link ServiceLoader#stream() stream()} method |
| * then the elements are of type {@code Provider}. This allows processing |
| * to select or filter on the provider class without instantiating the |
| * provider. </p> |
| * |
| * @param <S> The service type |
| * @since 9 |
| */ |
| public static interface Provider<S> extends Supplier<S> { |
| /** |
| * Returns the provider type. There is no guarantee that this type is |
| * accessible or that it has a public no-args constructor. The {@link |
| * #get() get()} method should be used to obtain the provider instance. |
| * |
| * <p> When a module declares that the provider class is created by a |
| * provider factory then this method returns the return type of its |
| * public static "{@code provider()}" method. |
| * |
| * @return The provider type |
| */ |
| Class<? extends S> type(); |
| |
| /** |
| * Returns an instance of the provider. |
| * |
| * @return An instance of the provider. |
| * |
| * @throws ServiceConfigurationError |
| * If the service provider cannot be instantiated, or in the |
| * case of a provider factory, the public static |
| * "{@code provider()}" method returns {@code null} or throws |
| * an error or exception. The {@code ServiceConfigurationError} |
| * will carry an appropriate cause where possible. |
| */ |
| @Override S get(); |
| } |
| |
| /** |
| * Initializes a new instance of this class for locating service providers |
| * in a module Layer. |
| * |
| * @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, Layer layer, Class<S> svc) { |
| Objects.requireNonNull(caller); |
| Objects.requireNonNull(layer); |
| Objects.requireNonNull(svc); |
| checkCaller(caller, svc); |
| |
| this.service = svc; |
| 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() + "]"; |
| } |
| |
| } |
