- /*
- * @(#)ServiceRegistry.java 1.18 03/01/23
- *
- * Copyright 2003 Sun Microsystems, Inc. All rights reserved.
- * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
- */
-
- package javax.imageio.spi;
-
- import java.io.File;
- import java.util.ArrayList;
- import java.util.HashMap;
- import java.util.Iterator;
- import java.util.List;
- import java.util.Map;
- import java.util.NoSuchElementException;
- import java.util.Set;
- import sun.misc.Service;
-
- /**
- * A registry for service provider instances.
- *
- * <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 interface or subclass the class defined by the
- * service itself.
- *
- * <p> Service providers are stored in one or more <i>categories</i>,
- * each of which is defined by a class of interface (described by a
- * <code>Class</code> object) that all of its members must implement.
- * The set of categories may be changed dynamically.
- *
- * <p> Only a single instance of a given leaf class (that is, the
- * actual class returned by <code>getClass()</code>, as opposed to any
- * inherited classes or interfaces) may be registered. That is,
- * suppose that the
- * <code>com.mycompany.mypkg.GreenServiceProvider</code> class
- * implements the <code>com.mycompany.mypkg.MyService</code>
- * interface. If a <code>GreenServiceProvider</code> instance is
- * registered, it will be stored in the category defined by the
- * <code>MyService</code> class. If a new instance of
- * <code>GreenServiceProvider</code> is registered, it will replace
- * the previous instance. In practice, service provider objects are
- * usually singletons so this behavior is appropriate.
- *
- * <p> To declare a service provider, a <code>services</code>
- * subdirectory is placed within the <code>META-INF</code> directory
- * that is present in every JAR file. This directory contains a file
- * for each service provider interface that has one or more
- * implementation classes present in the JAR file. For example, if
- * the JAR file contained a class named
- * <code>com.mycompany.mypkg.MyServiceImpl</code> which implements the
- * <code>javax.someapi.SomeService</code> interface, the JAR file
- * would contain a file named: <pre>
- * META-INF/services/javax.someapi.SomeService </pre>
- *
- * containing the line:
- *
- * <pre>
- * com.mycompany.mypkg.MyService
- * </pre>
- *
- * <p> The service provider classes should be to be lightweight and
- * quick to load. Implementations of these interfaces should avoid
- * complex dependencies on other classes and on native code. The usual
- * pattern for more complex services is to register a lightweight
- * proxy for the heavyweight service.
- *
- * <p> An application may customize the contents of a registry as it
- * sees fit, so long as it has the appropriate runtime permission.
- *
- * <p> For more details on declaring service providers, and the JAR
- * format in general, see the <a
- * href="http://java.sun.com/products/jdk/1.3/docs/guide/jar/jar.html">
- * JAR File Specification</a>.
- *
- * @see RegisterableService
- *
- * @version 0.5
- */
- public class ServiceRegistry {
-
- // Class -> Registry
- private Map categoryMap = new HashMap();
-
- /**
- * Constructs a <code>ServiceRegistry</code> instance with a
- * set of categories taken from the <code>categories</code>
- * argument.
- *
- * @param categories an <code>Iterator</code> containing
- * <code>Class</code> objects to be used to define categories.
- *
- * @exception IllegalArgumentException if
- * <code>categories</code> is <code>null</code>.
- */
- public ServiceRegistry(Iterator categories) {
- if (categories == null) {
- throw new IllegalArgumentException("categories == null!");
- }
- while (categories.hasNext()) {
- Class category = (Class)categories.next();
- SubRegistry reg = new SubRegistry(this, category);
- categoryMap.put(category, reg);
- }
- }
-
- // The following two methods expose functionality from
- // sun.misc.Service. If that class is made public, they may be
- // removed.
- //
- // The sun.misc.ServiceConfigurationError class may also be
- // exposed, in which case the references to 'an
- // <code>Error</code>' below should be changed to 'a
- // <code>ServiceConfigurationError</code>'.
-
- /**
- * Searches for implementations of a particular service class
- * using the given class loader.
- *
- * <p> This method transforms the name of the given service class
- * into a provider-configuration filename as described in the
- * class comment and then uses the <code>getResources</code>
- * method of the given class loader to find all available files
- * with that name. These files are then read and parsed to
- * produce a list of provider-class names. The iterator that is
- * returned uses the given class loader to look up and then
- * instantiate each element of the list.
- *
- * <p> Because it is possible for extensions to be installed into
- * a running Java virtual machine, this method may return
- * different results each time it is invoked.
- *
- * @param providerClass a <code>Class</code>object indicating the
- * class or interface of the service providers being detected.
- *
- * @param loader the class loader to be used to load
- * provider-configuration files and instantiate provider classes,
- * or <code>null</code> if the system class loader (or, failing that
- * the bootstrap class loader) is to be used.
- *
- * @return An <code>Iterator</code> that yields provider objects
- * for the given service, in some arbitrary order. The iterator
- * will throw an <code>Error</code> if a provider-configuration
- * file violates the specified format or if a provider class
- * cannot be found and instantiated.
- *
- * @exception IllegalArgumentException if
- * <code>providerClass</code> is <code>null</code>.
- */
- public static Iterator lookupProviders(Class providerClass,
- ClassLoader loader) {
- if (providerClass == null) {
- throw new IllegalArgumentException("providerClass == null!");
- }
- return Service.providers(providerClass, loader);
- }
-
- /**
- * Locates and incrementally instantiates the available providers
- * of a given service using the context class loader. This
- * convenience method is equivalent to:
- *
- * <pre>
- * ClassLoader cl = Thread.currentThread().getContextClassLoader();
- * return Service.providers(service, cl);
- * </pre>
- *
- * @param providerClass a <code>Class</code>object indicating the
- * class or interface of the service providers being detected.
- *
- * @return An <code>Iterator</code> that yields provider objects
- * for the given service, in some arbitrary order. The iterator
- * will throw an <code>Error</code> if a provider-configuration
- * file violates the specified format or if a provider class
- * cannot be found and instantiated.
- *
- * @exception IllegalArgumentException if
- * <code>providerClass</code> is <code>null</code>.
- */
- public static Iterator lookupProviders(Class providerClass) {
- if (providerClass == null) {
- throw new IllegalArgumentException("providerClass == null!");
- }
- return Service.providers(providerClass);
- }
-
- /**
- * Returns an <code>Iterator</code> of <code>Class</code> objects
- * indicating the current set of categories. The iterator will be
- * empty if no categories exist.
- *
- * @return an <code>Iterator</code> containing
- * <code>Class</code>objects.
- */
- public Iterator getCategories() {
- Set keySet = categoryMap.keySet();
- return keySet.iterator();
- }
-
- /**
- * Returns an Iterator containing the subregistries to which the
- * provider belongs.
- */
- private Iterator getSubRegistries(Object provider) {
- List l = new ArrayList();
- Iterator iter = categoryMap.keySet().iterator();
- while (iter.hasNext()) {
- Class c = (Class)iter.next();
- if (c.isAssignableFrom(provider.getClass())) {
- l.add((SubRegistry)categoryMap.get(c));
- }
- }
- return l.iterator();
- }
-
- /**
- * Adds a service provider object to the registry. The provider
- * is associated with the given category.
- *
- * <p> If <code>provider</code> implements the
- * <code>RegisterableService</code> interface, its
- * <code>onRegistration</code> method will be called. Its
- * <code>onDeregistration</code> method will be called each time
- * it is deregistered from a category, for example if a
- * category is removed or the registry is garbage collected.
- *
- * @param provider the service provide object to be registered.
- * @param category the category under which to register the
- * provider.
- *
- * @return true if no provider of the same class was previously
- * registered in the same category category.
- *
- * @exception IllegalArgumentException if <code>provider</code> is
- * <code>null</code>.
- * @exception IllegalArgumentException if there is no category
- * corresponding to <code>category</code>.
- * @exception ClassCastException if provider does not implement
- * the <code>Class</code> defined by <code>category</code>.
- */
- public boolean registerServiceProvider(Object provider,
- Class category) {
- if (provider == null) {
- throw new IllegalArgumentException("provider == null!");
- }
- SubRegistry reg = (SubRegistry)categoryMap.get(category);
- if (reg == null) {
- throw new IllegalArgumentException("category unknown!");
- }
- if (!category.isAssignableFrom(provider.getClass())) {
- throw new ClassCastException();
- }
-
- return reg.registerServiceProvider(provider);
- }
-
- /**
- * Adds a service provider object to the registry. The provider
- * is associated within each category present in the registry
- * whose <code>Class</code> it implements.
- *
- * <p> If <code>provider</code> implements the
- * <code>RegisterableService</code> interface, its
- * <code>onRegistration</code> method will be called once for each
- * category it is registered under. Its
- * <code>onDeregistration</code> method will be called each time
- * it is deregistered from a category or when the registry is
- * finalized.
- *
- * @param provider the service provider object to be registered.
- *
- * @exception IllegalArgumentException if
- * <code>provider</code> is <code>null</code>.
- */
- public void registerServiceProvider(Object provider) {
- if (provider == null) {
- throw new IllegalArgumentException("provider == null!");
- }
- Iterator regs = getSubRegistries(provider);
- while (regs.hasNext()) {
- SubRegistry reg = (SubRegistry)regs.next();
- reg.registerServiceProvider(provider);
- }
- }
-
- /**
- * Adds a set of service provider objects, taken from an
- * <code>Iterator</code> to the registry. Each provider is
- * associated within each category present in the registry whose
- * <code>Class</code> it implements.
- *
- * <p> For each entry of <code>providers</code> that implements
- * the <code>RegisterableService</code> interface, its
- * <code>onRegistration</code> method will be called once for each
- * category it is registered under. Its
- * <code>onDeregistration</code> method will be called each time
- * it is deregistered from a category or when the registry is
- * finalized.
- *
- * @param providers an Iterator containing service provider
- * objects to be registered.
- *
- * @exception IllegalArgumentException if <code>providers</code>
- * is <code>null</code> or contains a <code>null</code> entry.
- */
- public void registerServiceProviders(Iterator providers) {
- if (providers == null) {
- throw new IllegalArgumentException("provider == null!");
- }
- while (providers.hasNext()) {
- registerServiceProvider(providers.next());
- }
- }
-
- /**
- * Removes a service provider object from the given category. If
- * the provider was not previously registered, nothing happens and
- * <code>false</code> is returned. Otherwise, <code>true</code>
- * is returned. If an object of the same class as
- * <code>provider</code> but not equal (using <code>==</code>) to
- * <code>provider</code> is registered, it will not be
- * deregistered.
- *
- * <p> If <code>provider</code> implements the
- * <code>RegisterableService</code> interface, its
- * <code>onDeregistration</code> method will be called.
- *
- * @param provider the service provider object to be deregistered.
- * @param category the category from which to deregister the
- * provider.
- *
- * @return <code>true</code> if the provider was previously
- * registered in the same category category,
- * <code>false</code> otherwise.
- *
- * @exception IllegalArgumentException if <code>provider</code> is
- * <code>null</code>.
- * @exception IllegalArgumentException if there is no category
- * corresponding to <code>category</code>.
- * @exception ClassCastException if provider does not implement
- * the class defined by <code>category</code>.
- */
- public boolean deregisterServiceProvider(Object provider,
- Class category) {
- if (provider == null) {
- throw new IllegalArgumentException("provider == null!");
- }
- SubRegistry reg = (SubRegistry)categoryMap.get(category);
- if (reg == null) {
- throw new IllegalArgumentException("category unknown!");
- }
- if (!category.isAssignableFrom(provider.getClass())) {
- throw new ClassCastException();
- }
- return reg.deregisterServiceProvider(provider);
- }
-
- /**
- * Removes a service provider object from all categories that
- * contain it.
- *
- * @param provider the service provider object to be deregistered.
- *
- * @exception IllegalArgumentException if <code>provider</code> is
- * <code>null</code>.
- */
- public void deregisterServiceProvider(Object provider) {
- if (provider == null) {
- throw new IllegalArgumentException("provider == null!");
- }
- Iterator regs = getSubRegistries(provider);
- while (regs.hasNext()) {
- SubRegistry reg = (SubRegistry)regs.next();
- reg.deregisterServiceProvider(provider);
- }
- }
-
- /**
- * Returns <code>true</code> if <code>provider</code> is currently
- * registered.
- *
- * @param provider the service provider object to be queried.
- *
- * @return <code>true</code> if the given provider has been
- * registered.
- *
- * @exception IllegalArgumentException if <code>provider</code> is
- * <code>null</code>.
- */
- public boolean contains(Object provider) {
- if (provider == null) {
- throw new IllegalArgumentException("provider == null!");
- }
- Iterator regs = getSubRegistries(provider);
- while (regs.hasNext()) {
- SubRegistry reg = (SubRegistry)regs.next();
- if (reg.contains(provider)) {
- return true;
- }
- }
-
- return false;
- }
-
- /**
- * Returns an <code>Iterator</code> containing all registered
- * service providers in the given category. If
- * <code>useOrdering</code> is <code>false</code>, the iterator
- * will return all of the server provider objects in an arbitrary
- * order. Otherwise, the ordering will respect any pairwise
- * orderings that have been set. If the graph of pairwise
- * orderings contains cycles, any providers that belong to a cycle
- * will not be returned.
- *
- * @param category the category to be retrieved from.
- * @param useOrdering <code>true</code> if pairwise orderings
- * should be taken account in ordering the returned objects.
- *
- * @return an <code>Iterator</code> containing service provider
- * objects from the given category, possibly in order.
- *
- * @exception IllegalArgumentException if there is no category
- * corresponding to <code>category</code>.
- */
- public Iterator getServiceProviders(Class category,
- boolean useOrdering) {
- SubRegistry reg = (SubRegistry)categoryMap.get(category);
- if (reg == null) {
- throw new IllegalArgumentException("category unknown!");
- }
- return reg.getServiceProviders(useOrdering);
- }
-
- /**
- * A simple filter interface used by
- * <code>ServiceRegistry.getServiceProviders</code> to select
- * providers matching an arbitrary criterion. Classes that
- * implement this interface should be defined in order to make use
- * of the <code>getServiceProviders</code> method of
- * <code>ServiceRegistry</code> that takes a <code>Filter</code>.
- *
- * @see ServiceRegistry#getServiceProviders(Class, ServiceRegistry.Filter, boolean)
- */
- public interface Filter {
-
- /**
- * Returns <code>true</code> if the given
- * <code>provider</code> object matches the criterion defined
- * by this <code>Filter</code>.
- *
- * @param provider a service provider <code>Object</code>.
- *
- * @return true if the provider matches the criterion.
- */
- boolean filter(Object provider);
- }
-
- /**
- * Returns an <code>Iterator</code> containing service provider
- * objects within a given category that satisfy a criterion
- * imposed by the supplied <code>ServiceRegistry.Filter</code>
- * object's <code>filter</code> method.
- *
- * <p> The <code>useOrdering</code> argument controls the
- * ordering of the results using the same rules as
- * <code>getServiceProviders(Class, boolean)</code>.
- *
- * @param category the category to be retrieved from.
- * @param filter an instance of <code>ServiceRegistry.Filter</code>
- * whose <code>filter</code> method will be invoked.
- * @param useOrdering <code>true</code> if pairwise orderings
- * should be taken account in ordering the returned objects.
- *
- * @return an <code>Iterator</code> containing service provider
- * objects from the given category, possibly in order.
- *
- * @exception IllegalArgumentException if there is no category
- * corresponding to <code>category</code>.
- */
- public Iterator getServiceProviders(Class category,
- Filter filter,
- boolean useOrdering) {
- SubRegistry reg = (SubRegistry)categoryMap.get(category);
- if (reg == null) {
- throw new IllegalArgumentException("category unknown!");
- }
- Iterator iter = getServiceProviders(category, useOrdering);
- return new FilterIterator(iter, filter);
- }
-
- /**
- * Returns the currently registered service provider object that
- * is of the given class type. At most one object of a given
- * class is allowed to be registered at any given time. If no
- * registered object has the desired class type, <code>null</code>
- * is returned.
- *
- * @param providerClass the <code>Class</code> of the desired
- * service provider object.
- *
- * @return a currently registered service provider object with the
- * desired <code>Class</code>type, or <code>null</code> is none is
- * present.
- *
- * @exception IllegalArgumentException if <code>providerClass</code> is
- * <code>null</code>.
- */
- public Object getServiceProviderByClass(Class providerClass) {
- if (providerClass == null) {
- throw new IllegalArgumentException("providerClass == null!");
- }
- Iterator iter = categoryMap.keySet().iterator();
- while (iter.hasNext()) {
- Class c = (Class)iter.next();
- if (c.isAssignableFrom(providerClass)) {
- SubRegistry reg = (SubRegistry)categoryMap.get(c);
- Object provider = reg.getServiceProviderByClass(providerClass);
- if (provider != null) {
- return provider;
- }
- }
- }
- return null;
- }
-
- /**
- * Sets a pairwise ordering between two service provider objects
- * within a given category. If one or both objects are not
- * currently registered within the given category, or if the
- * desired ordering is already set, nothing happens and
- * <code>false</code> is returned. If the providers previously
- * were ordered in the reverse direction, that ordering is
- * removed.
- *
- * <p> The ordering will be used by the
- * <code>getServiceProviders</code> methods when their
- * <code>useOrdering</code> argument is <code>true</code>.
- *
- * @param category a <code>Class</code> object indicating the
- * category under which the preference is to be established.
- * @param firstProvider the preferred provider.
- * @param secondProvider the provider to which
- * <code>firstProvider</code> is preferred.
- *
- * @return <code>true</code> if a previously unset ordering
- * was established.
- *
- * @exception IllegalArgumentException if either provider is
- * <code>null</code> or they are the same object.
- * @exception IllegalArgumentException if there is no category
- * corresponding to <code>category</code>.
- */
- public boolean setOrdering(Class category,
- Object firstProvider,
- Object secondProvider) {
- if (firstProvider == null || secondProvider == null) {
- throw new IllegalArgumentException("provider is null!");
- }
- if (firstProvider == secondProvider) {
- throw new IllegalArgumentException("providers are the same!");
- }
- SubRegistry reg = (SubRegistry)categoryMap.get(category);
- if (reg == null) {
- throw new IllegalArgumentException("category unknown!");
- }
- if (reg.contains(firstProvider) &&
- reg.contains(secondProvider)) {
- return reg.setOrdering(firstProvider, secondProvider);
- }
- return false;
- }
-
- /**
- * Sets a pairwise ordering between two service provider objects
- * within a given category. If one or both objects are not
- * currently registered within the given category, or if no
- * ordering is currently set between them, nothing happens
- * and <code>false</code> is returned.
- *
- * <p> The ordering will be used by the
- * <code>getServiceProviders</code> methods when their
- * <code>useOrdering</code> argument is <code>true</code>.
- *
- * @param category a <code>Class</code> object indicating the
- * category under which the preference is to be disestablished.
- * @param firstProvider the formerly preferred provider.
- * @param secondProvider the provider to which
- * <code>firstProvider</code> was formerly preferred.
- *
- * @return <code>true</code> if a previously set ordering was
- * disestablished.
- *
- * @exception IllegalArgumentException if either provider is
- * <code>null</code> or they are the same object.
- * @exception IllegalArgumentException if there is no category
- * corresponding to <code>category</code>.
- */
- public boolean unsetOrdering(Class category,
- Object firstProvider,
- Object secondProvider) {
- if (firstProvider == null || secondProvider == null) {
- throw new IllegalArgumentException("provider is null!");
- }
- if (firstProvider == secondProvider) {
- throw new IllegalArgumentException("providers are the same!");
- }
- SubRegistry reg = (SubRegistry)categoryMap.get(category);
- if (reg == null) {
- throw new IllegalArgumentException("category unknown!");
- }
- if (reg.contains(firstProvider) &&
- reg.contains(secondProvider)) {
- return reg.unsetOrdering(firstProvider, secondProvider);
- }
- return false;
- }
-
- /**
- * Deregisters all service provider object currently registered
- * under the given category.
- *
- * @param category the category to be emptied.
- *
- * @exception IllegalArgumentException if there is no category
- * corresponding to <code>category</code>.
- */
- public void deregisterAll(Class category) {
- SubRegistry reg = (SubRegistry)categoryMap.get(category);
- if (reg == null) {
- throw new IllegalArgumentException("category unknown!");
- }
- reg.clear();
- }
-
- /**
- * Deregisters all currently registered service providers from all
- * categories.
- */
- public void deregisterAll() {
- Iterator iter = categoryMap.values().iterator();
- while (iter.hasNext()) {
- SubRegistry reg = (SubRegistry)iter.next();
- reg.clear();
- }
- categoryMap.clear();
- }
-
- /**
- * Finalizes this object prior to garbage collection. The
- * <code>deregisterAll</code> method is called to deregister all
- * currently registered service providers. This method should not
- * be called from application code.
- *
- * @exception Throwable if an error occurs during superclass
- * finalization.
- */
- public void finalize() throws Throwable {
- deregisterAll();
- super.finalize();
- }
- }
-
-
- /**
- * A portion of a registry dealing with a single superclass or
- * interface.
- */
- class SubRegistry {
-
- ServiceRegistry registry;
-
- Class category;
-
- // Provider Objects organized by partial oridering
- PartiallyOrderedSet poset = new PartiallyOrderedSet();
-
- // Class -> Provider Object of that class
- Map map = new HashMap();
-
- public SubRegistry(ServiceRegistry registry, Class category) {
- this.registry = registry;
- this.category = category;
- }
-
- public boolean registerServiceProvider(Object provider) {
- boolean present = map.get(provider.getClass()) != null;
-
- map.put(provider.getClass(), provider);
- poset.add(provider);
- if (provider instanceof RegisterableService) {
- RegisterableService rs = (RegisterableService)provider;
- rs.onRegistration(registry, category);
- }
-
- return !present;
- }
-
- /**
- * If the provider was not previously registered, do nothing.
- *
- * @return true if the provider was previously registered.
- */
- public boolean deregisterServiceProvider(Object provider) {
- Object oprovider = map.get(provider.getClass());
-
- if (provider == oprovider) {
- map.remove(provider.getClass());
- poset.remove(provider);
- if (provider instanceof RegisterableService) {
- RegisterableService rs = (RegisterableService)provider;
- rs.onDeregistration(registry, category);
- }
-
- return true;
- }
- return false;
- }
-
- public boolean contains(Object provider) {
- Object oprovider = map.get(provider.getClass());
- return oprovider == provider;
- }
-
- public boolean setOrdering(Object firstProvider,
- Object secondProvider) {
- return poset.setOrdering(firstProvider, secondProvider);
- }
-
- public boolean unsetOrdering(Object firstProvider,
- Object secondProvider) {
- return poset.unsetOrdering(firstProvider, secondProvider);
- }
-
- public Iterator getServiceProviders(boolean useOrdering) {
- if (useOrdering) {
- return poset.iterator();
- } else {
- return map.values().iterator();
- }
- }
-
- public Object getServiceProviderByClass(Class providerClass) {
- return map.get(providerClass);
- }
-
- public void clear() {
- Iterator iter = map.values().iterator();
- while (iter.hasNext()) {
- Object provider = iter.next();
- iter.remove();
-
- if (provider instanceof RegisterableService) {
- RegisterableService rs = (RegisterableService)provider;
- rs.onDeregistration(registry, category);
- }
- }
- poset.clear();
- }
-
- public void finalize() {
- clear();
- }
- }
-
-
- /**
- * A class for wrapping <code>Iterators</code> with a filter function.
- * This provides an iterator for a subset without duplication.
- */
- class FilterIterator implements Iterator {
-
- private Iterator iter;
- private ServiceRegistry.Filter filter;
-
- private Object next = null;
-
- public FilterIterator(Iterator iter,
- ServiceRegistry.Filter filter) {
- this.iter = iter;
- this.filter = filter;
- advance();
- }
-
- private void advance() {
- while (iter.hasNext()) {
- Object elt = iter.next();
- if (filter.filter(elt)) {
- next = elt;
- return;
- }
- }
-
- next = null;
- }
-
- public boolean hasNext() {
- return next != null;
- }
-
- public Object next() {
- if (next == null) {
- throw new NoSuchElementException();
- }
- Object o = next;
- advance();
- return o;
- }
-
- public void remove() {
- throw new UnsupportedOperationException();
- }
- }