jdk8-mips64-public/langtools: src/share/classes/com/sun/tools/javac/util/ServiceLoader.java@93012e2a5d1d (annotated)

src/share/classes/com/sun/tools/javac/util/ServiceLoader.java@93012e2a5d1d (annotated)

src/share/classes/com/sun/tools/javac/util/ServiceLoader.java

Sat, 07 Nov 2020 10:30:02 +0800

author: aoqi
date: Sat, 07 Nov 2020 10:30:02 +0800
changeset 3938: 93012e2a5d1d
parent 0: 959103a6100f
permissions: -rw-r--r--

Added tag mips-jdk8u275-b01 for changeset eb6ee6a5f2fe

 /*
  * Copyright (c) 2005, 2013, 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 com.sun.tools.javac.util;
 import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.net.URL;
 import java.net.URLConnection;
 import java.util.ArrayList;
 import java.util.Enumeration;
 import java.util.Iterator;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.NoSuchElementException;
 import java.util.Objects;
 import java.util.ServiceConfigurationError;
 /**
  * This is a temporary, modified copy of java.util.ServiceLoader, for use by
  * javac, to work around bug JDK-8004082.
  *
  * The bug describes problems in the interaction between ServiceLoader and
  * URLClassLoader, such that references to a jar file passed to URLClassLoader
  * may be retained after calling URLClassLoader.close(), preventing the jar
  * file from being deleted on Windows.
  *
  *  <p><b>This is NOT part of any supported API.
  *  If you write code that depends on this, you do so at your own risk.
  *  This code and its internal interfaces are subject to change or
  *  deletion without notice.</b>
  */
 public final class ServiceLoader<S>
     implements Iterable<S>
 {
     private static final String PREFIX = "META-INF/services/";
     // The class or interface representing the service being loaded
     private Class<S> service;
     // The class loader used to locate, load, and instantiate providers
     private ClassLoader loader;
     // Cached providers, in instantiation order
     private LinkedHashMap<String,S> providers = new LinkedHashMap<>();
     // The current lazy-lookup iterator
     private LazyIterator lookupIterator;
     /**
      * 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} method will lazily look up and instantiate
      * providers 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() {
         providers.clear();
         lookupIterator = new LazyIterator(service, loader);
     }
     private ServiceLoader(Class<S> svc, ClassLoader cl) {
         service = Objects.requireNonNull(svc, "Service interface cannot be null");
         loader = (cl == null) ? ClassLoader.getSystemClassLoader() : cl;
         reload();
     }
     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);
     }
     // Parse a single line from the given configuration file, adding the name
     // on the line to the names list.
     //
     private int parseLine(Class<?> service, URL u, BufferedReader r, int lc,
                           List<String> names)
         throws IOException, ServiceConfigurationError
     {
         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);
             for (int i = Character.charCount(cp); i < n; i += Character.charCount(cp)) {
                 cp = ln.codePointAt(i);
                 if (!Character.isJavaIdentifierPart(cp) && (cp != '.'))
                     fail(service, u, lc, "Illegal provider-class name: " + ln);
             }
             if (!providers.containsKey(ln) && !names.contains(ln))
                 names.add(ln);
         }
         return lc + 1;
     }
     // Parse the content of the given URL as a provider-configuration file.
     //
     // @param  service
     //         The service type for which providers are being sought;
     //         used to construct error detail strings
     //
     // @param  u
     //         The URL naming the configuration file to be parsed
     //
     // @return A (possibly empty) iterator that will yield the provider-class
     //         names in the given configuration file that are not yet members
     //         of the returned set
     //
     // @throws ServiceConfigurationError
     //         If an I/O error occurs while reading from the given URL, or
     //         if a configuration-file format error is detected
     //
     private Iterator<String> parse(Class<?> service, URL u)
         throws ServiceConfigurationError
     {
         InputStream in = null;
         BufferedReader r = null;
         ArrayList<String> names = new ArrayList<>();
         try {
             // The problem is that by default, streams opened with
             // u.openInputStream use a cached reference to a JarFile, which
             // is separate from the reference used by URLClassLoader, and
             // which is not closed by URLClassLoader.close().
             // The workaround is to disable caching for this specific jar file,
             // so that the reference to the jar file can be closed when the
             // file has been read.
             // Original code:
             // in = u.openStream();
             // Workaround ...
             URLConnection uc = u.openConnection();
             uc.setUseCaches(false);
             in = uc.getInputStream();
             // ... end of workaround.
             r = new BufferedReader(new InputStreamReader(in, "utf-8"));
             int lc = 1;
             while ((lc = parseLine(service, u, r, lc, names)) >= 0);
         } catch (IOException x) {
             fail(service, "Error reading configuration file", x);
         } finally {
             try {
                 if (r != null) r.close();
                 if (in != null) in.close();
             } catch (IOException y) {
                 fail(service, "Error closing configuration file", y);
             }
         }
         return names.iterator();
     }
     // Private inner class implementing fully-lazy provider lookup
     //
     private class LazyIterator
         implements Iterator<S>
     {
         Class<S> service;
         ClassLoader loader;
         Enumeration<URL> configs = null;
         Iterator<String> pending = null;
         String nextName = null;
         private LazyIterator(Class<S> service, ClassLoader loader) {
             this.service = service;
             this.loader = loader;
         }
         public boolean hasNext() {
             if (nextName != null) {
                 return true;
             }
             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(service, configs.nextElement());
             }
             nextName = pending.next();
             return true;
         }
         public S next() {
             if (!hasNext()) {
                 throw new NoSuchElementException();
             }
             String cn = nextName;
             nextName = null;
             Class<?> c = null;
             try {
                 c = Class.forName(cn, false, loader);
             } catch (ClassNotFoundException x) {
                 fail(service,
                      "Provider " + cn + " not found");
             }
             if (!service.isAssignableFrom(c)) {
                 fail(service,
                      "Provider " + cn  + " not a subtype");
             }
             try {
                 S p = service.cast(c.newInstance());
                 providers.put(cn, p);
                 return p;
             } catch (Throwable x) {
                 fail(service,
                      "Provider " + cn + " could not be instantiated: " + x,
                      x);
             }
             throw new Error();          // This cannot happen
         }
         public void remove() {
             throw new UnsupportedOperationException();
         }
     }
     /**
      * Lazily loads 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 instantiation order.  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 parsing the available
      * provider-configuration files 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-configuration file
      * violates the specified format, or if it names a provider class that
      * cannot be found and instantiated, or if the result of instantiating the
      * class is not assignable to the service type, or if any other kind of
      * exception or error is thrown as the next provider is located and
      * instantiated.  To write robust code it is only necessary to catch {@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> 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() {
         return new Iterator<S>() {
             Iterator<Map.Entry<String,S>> knownProviders
                 = providers.entrySet().iterator();
             public boolean hasNext() {
                 if (knownProviders.hasNext())
                     return true;
                 return lookupIterator.hasNext();
             }
             public S next() {
                 if (knownProviders.hasNext())
                     return knownProviders.next().getValue();
                 return lookupIterator.next();
             }
             public void remove() {
                 throw new UnsupportedOperationException();
             }
         };
     }
     /**
      * Creates a new service loader for the given service type and class
      * loader.
      *
      * @param  service
      *         The interface or abstract class representing the service
      *
      * @param  loader
      *         The class loader to be used to load provider-configuration files
      *         and provider classes, or <tt>null</tt> if the system class
      *         loader (or, failing that, the bootstrap class loader) is to be
      *         used
      *
      * @return A new service loader
      */
     public static <S> ServiceLoader<S> load(Class<S> service,
                                             ClassLoader loader)
     {
         return new ServiceLoader<>(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
      *
      * <blockquote><pre>
      * ServiceLoader.load(<i>service</i>)</pre></blockquote>
      *
      * is equivalent to
      *
      * <blockquote><pre>
      * ServiceLoader.load(<i>service</i>,
      *                    Thread.currentThread().getContextClassLoader())</pre></blockquote>
      *
      * @param  service
      *         The interface or abstract class representing the service
      *
      * @return A new service loader
      */
     public static <S> ServiceLoader<S> load(Class<S> service) {
         ClassLoader cl = Thread.currentThread().getContextClassLoader();
         return ServiceLoader.load(service, cl);
     }
     /**
      * Creates a new service loader for the given service type, using the
      * extension class loader.
      *
      * <p> This convenience method simply locates the extension class loader,
      * call it <tt><i>extClassLoader</i></tt>, and then returns
      *
      * <blockquote><pre>
      * ServiceLoader.load(<i>service</i>, <i>extClassLoader</i>)</pre></blockquote>
      *
      * <p> If the extension class loader cannot be found then the system class
      * loader is used; if there is no system class loader then the bootstrap
      * class loader is used.
      *
      * <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 class path will be ignored.
      *
      * @param  service
      *         The interface or abstract class representing the service
      *
      * @return A new service loader
      */
     public static <S> ServiceLoader<S> loadInstalled(Class<S> service) {
         ClassLoader cl = ClassLoader.getSystemClassLoader();
         ClassLoader prev = null;
         while (cl != null) {
             prev = cl;
             cl = cl.getParent();
         }
         return ServiceLoader.load(service, prev);
     }
     /**
      * Returns a string describing this service.
      *
      * @return  A descriptive string
      */
     public String toString() {
         return "java.util.ServiceLoader[" + service.getName() + "]";
     }
 }

Mercurial > jdk8-mips64-public > langtools / annotate

src/share/classes/com/sun/tools/javac/util/ServiceLoader.java@93012e2a5d1d (annotated)

src/share/classes/com/sun/tools/javac/util/ServiceLoader.java