Mercurial > jdk8-mips64-public > jaxws / file revision

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  * 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

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 package com.sun.xml.internal.ws.policy.privateutil;

 import java.io.BufferedReader;

 import java.io.IOException;

 import java.io.InputStream;

 import java.io.InputStreamReader;

 import java.lang.reflect.Array;

 import java.net.URL;

 import java.util.ArrayList;

 import java.util.Enumeration;

 import java.util.Iterator;

 import java.util.List;

 import java.util.NoSuchElementException;

 import java.util.Set;

 import java.util.TreeSet;

 /**

  *

  * A simple service-provider lookup mechanism.  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.  Service providers may be installed in an

  * implementation of the Java platform in the form of extensions, that is, jar

  * files placed into any of the usual extension directories.  Providers may

  * also be made available by adding them to the applet or application class

  * path or by some other platform-specific means.

  * <p/>

  * <p> In this lookup mechanism a service is represented by an interface or an

  * abstract class.  (A concrete class may be used, but this is not

  * recommended.)  A provider of a given service contains one or more concrete

  * classes that extend this <i>service class</i> with data and code specific to

  * the provider.  This <i>provider class</i> will typically not be the entire

  * provider itself but rather a proxy that 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 class has been defined.  The

  * only requirement enforced here is that provider classes must have a

  * zero-argument constructor so that they may be instantiated during lookup.

  * <p/>

  * <p> A service provider identifies itself by placing a provider-configuration

  * file in the resource directory <tt>META-INF/services</tt>.  The file's name

  * should consist of the fully-qualified name of the abstract service class.

  * The file should contain a list of fully-qualified concrete provider-class

  * names, one per line.  Space and tab characters surrounding each name, as

  * well as blank lines, are ignored.  The comment character is <tt>'#'</tt>

  * (<tt>0x23</tt>); on each line all characters following the first comment

  * character are ignored.  The file must be encoded in UTF-8.

  * <p/>

  * <p> 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 will be 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 accessible from the same

  * class loader that was initially queried to locate the configuration file;

  * note that this is not necessarily the class loader that found the file.

  * <p/>

  * <p> <b>Example:</b> Suppose we have a service class named

  * <tt>java.io.spi.CharCodec</tt>.  It has two abstract methods:

  * <p/>

  * <pre>

  *   public abstract CharEncoder getEncoder(String encodingName);

  *   public abstract CharDecoder getDecoder(String encodingName);

  * </pre>

  * <p/>

  * Each method returns an appropriate object or <tt>null</tt> if it cannot

  * translate the given encoding.  Typical <tt>CharCodec</tt> providers will

  * support more than one encoding.

  * <p/>

  * <p> If <tt>sun.io.StandardCodec</tt> is a provider of the <tt>CharCodec</tt>

  * service then its jar file would contain the file

  * <tt>META-INF/services/java.io.spi.CharCodec</tt>.  This file would contain

  * the single line:

  * <p/>

  * <pre>

  *   sun.io.StandardCodec    # Standard codecs for the platform

  * </pre>

  * <p/>

  * To locate an encoder for a given encoding name, the internal I/O code would

  * do something like this:

  * <p/>

  * <pre>

  *   CharEncoder getEncoder(String encodingName) {

  *       for( CharCodec cc : ServiceFinder.find(CharCodec.class) ) {

  *           CharEncoder ce = cc.getEncoder(encodingName);

  *           if (ce != null)

  *               return ce;

  *       }

  *       return null;

  *   }

  * </pre>

  * <p/>

  * The provider-lookup mechanism always executes in the security context of the

  * caller.  Trusted system code should typically invoke the methods in this

  * class from within a privileged security context.

  *

  * @author Mark Reinhold

  * @version 1.11, 03/12/19

  * @since 1.3

  */

 final class ServiceFinder<T> implements Iterable<T> {

     private static final PolicyLogger LOGGER = PolicyLogger.getLogger(ServiceFinder.class);

     private static final String prefix = "META-INF/services/";

     private final Class<T> serviceClass;

     private final ClassLoader classLoader;

     /**

      * Locates and incrementally instantiates the available providers of a

      * given service using the given class loader.

      * <p/>

      * <p> This method transforms the name of the given service class into a

      * provider-configuration filename as described above and then uses the

      * <tt>getResources</tt> 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 lookup and then instantiate each element

      * of the list.

      * <p/>

      * <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. <p>

      *

      * @param service The service's abstract service class

      * @param loader  The class loader to be used to load provider-configuration files

      *                and instantiate provider classes, or <tt>null</tt> if the system

      *                class loader (or, failing that the bootstrap class loader) is to

      *                be used

      * @throws ServiceConfigurationError If a provider-configuration file violates the specified format

      *                                   or names a provider class that cannot be found and instantiated

      * @see #find(Class)

      */

     static <T> ServiceFinder<T> find(final Class<T> service, final ClassLoader loader) {

         if (null==service) {

             throw LOGGER.logSevereException(new NullPointerException(LocalizationMessages.WSP_0032_SERVICE_CAN_NOT_BE_NULL()));

         }

         return new ServiceFinder<T>(service,loader);

     }

     /**

      * Locates and incrementally instantiates the available providers of a

      * given service using the context class loader.  This convenience method

      * is equivalent to

      * <p/>

      * <pre>

      *   ClassLoader cl = Thread.currentThread().getContextClassLoader();

      *   return Service.providers(service, cl);

      * </pre>

      *

      * @param service The service's abstract service class

      *

      * @throws ServiceConfigurationError If a provider-configuration file violates the specified format

      *                                   or names a provider class that cannot be found and instantiated

      * @see #find(Class, ClassLoader)

      */

     public static <T> ServiceFinder<T> find(final Class<T> service) {

         return find(service,Thread.currentThread().getContextClassLoader());

     }

     private ServiceFinder(Class<T> service, ClassLoader loader) {

         this.serviceClass = service;

         this.classLoader = loader;

     }

     /**

      * Returns discovered objects incrementally.

      *

      * @return An <tt>Iterator</tt> that yields provider objects for the given

      *         service, in some arbitrary order.  The iterator will throw a

      *         <tt>ServiceConfigurationError</tt> if a provider-configuration

      *         file violates the specified format or if a provider class cannot

      *         be found and instantiated.

      */

     public Iterator<T> iterator() {

         return new LazyIterator<T>(serviceClass,classLoader);

     }

     /**

      * Returns discovered objects all at once.

      *

      * @return

      *      can be empty but never null.

      *

      * @throws ServiceConfigurationError

      */

     @SuppressWarnings({"unchecked"})

     public T[] toArray() {

         List<T> result = new ArrayList<T>();

         for (T t : this) {

             result.add(t);

         }

         return result.toArray((T[])Array.newInstance(serviceClass,result.size()));

     }

     private static void fail(final Class service, final String msg, final Throwable cause)

         throws ServiceConfigurationError {

         final ServiceConfigurationError sce

             = new ServiceConfigurationError(LocalizationMessages.WSP_0025_SPI_FAIL_SERVICE_MSG(service.getName(), msg));

         if (null != cause) {

             sce.initCause(cause);

         }

         throw LOGGER.logSevereException(sce);

     }

 /*    private static void fail(Class service, String msg)

         throws ServiceConfigurationError {

         throw new ServiceConfigurationError(LocalizationMessages.WSP_0025_SPI_FAIL_SERVICE_MSG(service.getName(), msg));

     }*/

     private static void fail(final Class service, final URL u, final int line, final String msg, final Throwable cause)

         throws ServiceConfigurationError {

         fail(service, LocalizationMessages.WSP_0024_SPI_FAIL_SERVICE_URL_LINE_MSG(u , line, msg), cause);

     }

     /**

      * Parse a single line from the given configuration file, adding the name

      * on the line to both the names list and the returned set iff the name is

      * not already a member of the returned set.

      */

     private static int parseLine(final Class service, final URL u, final BufferedReader r, final int lc,

                                  final List<String> names, final Set<String> returned)

         throws IOException, ServiceConfigurationError {

         String ln = r.readLine();

         if (ln == null) {

             return -1;

         }

         final int ci = ln.indexOf('#');

         if (ci >= 0) ln = ln.substring(0, ci);

         ln = ln.trim();

         final int n = ln.length();

         if (n != 0) {

             if ((ln.indexOf(' ') >= 0) || (ln.indexOf('\t') >= 0))

                 fail(service, u, lc, LocalizationMessages.WSP_0067_ILLEGAL_CFG_FILE_SYNTAX(), null);

             int cp = ln.codePointAt(0);

             if (!Character.isJavaIdentifierStart(cp))

                 fail(service, u, lc, LocalizationMessages.WSP_0066_ILLEGAL_PROVIDER_CLASSNAME(ln), null);

             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, LocalizationMessages.WSP_0066_ILLEGAL_PROVIDER_CLASSNAME(ln), null);

             }

             if (!returned.contains(ln)) {

                 names.add(ln);

                 returned.add(ln);

             }

         }

         return lc + 1;

     }

     /**

      * Parse the content of the given URL as a provider-configuration file.

      *

      * @param service  The service class for which providers are being sought;

      *                 used to construct error detail strings

      * @param u        The URL naming the configuration file to be parsed

      * @param returned A Set containing the names of provider classes that have already

      *                 been returned.  This set will be updated to contain the names

      *                 that will be yielded from the returned <tt>Iterator</tt>.

      * @return A (possibly empty) <tt>Iterator</tt> 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

      */

     @SuppressWarnings({"StatementWithEmptyBody"})

     private static Iterator<String> parse(Class service, URL u, Set<String> returned)

         throws ServiceConfigurationError {

         InputStream in = null;

         BufferedReader r = null;

         ArrayList<String> names = new ArrayList<String>();

         try {

             in = u.openStream();

             r = new BufferedReader(new InputStreamReader(in, "utf-8"));

             int lc = 1;

             while ((lc = parseLine(service, u, r, lc, names, returned)) >= 0) ;

         } catch (IOException x) {

             fail(service, ": " + x, x);

         } finally {

             try {

                 if (r != null) r.close();

                 if (in != null) in.close();

             } catch (IOException y) {

                 fail(service, ": " + y, y);

             }

         }

         return names.iterator();

     }

     /**

      * Private inner class implementing fully-lazy provider lookup

      */

     private static class LazyIterator<T> implements Iterator<T> {

         Class<T> service;

         ClassLoader loader;

         Enumeration<URL> configs = null;

         Iterator<String> pending = null;

         Set<String> returned = new TreeSet<String>();

         String nextName = null;

         private LazyIterator(Class<T> service, ClassLoader loader) {

             this.service = service;

             this.loader = loader;

         }

         public boolean hasNext() throws ServiceConfigurationError {

             if (nextName != null) {

                 return true;

             }

             if (configs == null) {

                 try {

                     final String fullName = prefix + service.getName();

                     if (loader == null)

                         configs = ClassLoader.getSystemResources(fullName);

                     else

                         configs = loader.getResources(fullName);

                 } catch (IOException x) {

                     fail(service, ": " + x, x);

                 }

             }

             while ((pending == null) || !pending.hasNext()) {

                 if (!configs.hasMoreElements()) {

                     return false;

                 }

                 pending = parse(service, configs.nextElement(), returned);

             }

             nextName = pending.next();

             return true;

         }

         public T next() throws ServiceConfigurationError {

             if (!hasNext()) {

                 throw new NoSuchElementException();

             }

             final String cn = nextName;

             nextName = null;

             try {

                 return service.cast(Class.forName(cn, true, loader).newInstance());

             } catch (ClassNotFoundException x) {

                 fail(service, LocalizationMessages.WSP_0027_SERVICE_PROVIDER_NOT_FOUND(cn), x);

             } catch (Exception x) {

                 fail(service, LocalizationMessages.WSP_0028_SERVICE_PROVIDER_COULD_NOT_BE_INSTANTIATED(cn), x);

             }

             return null;    /* This cannot happen */

         }

         public void remove() {

             throw new UnsupportedOperationException();

         }

     }

 }