src/javax/persistence/spi/PersistenceProviderResolverHolder.java - eclipselink/javax.persistence - Git at Google

 /*******************************************************************************
  * Copyright (c) 2008, 2009 Sun Microsystems. All rights reserved.
  *
  * This program and the accompanying materials are made available under the
  * terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
  * which accompanies this distribution.
  * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
  * and the Eclipse Distribution License is available at
  * http://www.eclipse.org/org/documents/edl-v10.php.
  *
  * Contributors:
  *     Linda DeMichiel - Java Persistence 2.0 - Version 2.0 (October 1, 2009)
  *     Specification available from http://jcp.org/en/jsr/detail?id=317
  *     dclarke - EclipseLink implementation and default resolver
  *
  ******************************************************************************/
 package javax.persistence.spi;

 import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.lang.ref.ReferenceQueue;
 import java.lang.ref.SoftReference;
 import java.lang.ref.WeakReference;
 import java.net.URL;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Enumeration;
 import java.util.List;
 import java.util.HashMap;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;

 import javax.persistence.PersistenceException;

 /**
  * Holds the global {@link javax.persistence.spi.PersistenceProviderResolver}
  * instance. If no <code>PersistenceProviderResolver</code> is set by the
  * environment, the default </code>PersistenceProviderResolver is used.
  *
  * Implementations must be thread-safe.
  *
  * @since Java Persistence 2.0
  */
 public class PersistenceProviderResolverHolder {

     private static PersistenceProviderResolver singleton = new DefaultPersistenceProviderResolver();

     /**
      * Returns the current persistence provider resolver.
      *
      * @return the current persistence provider resolver
      */
     public static PersistenceProviderResolver getPersistenceProviderResolver() {
         return singleton;
     }

     /**
      * Defines the persistence provider resolver used.
      *
      * @param resolver persistence provider resolver to be used.
      */
     public static void setPersistenceProviderResolver(PersistenceProviderResolver resolver) {
         if (resolver == null) {
             singleton = new DefaultPersistenceProviderResolver();
         } else {
             singleton = resolver;
         }
     }

     /**
      * Default provider resolver class to use when none is explicitly set.
      *
      * Uses the META-INF/services approach as described in the Java Persistence
      * specification. A getResources() call is made on the current context
      * classloader to find the service provider files on the classpath. Any
      * service files found are then read to obtain the classes that implement
      * the persistence provider interface.
      */
     private static class DefaultPersistenceProviderResolver implements PersistenceProviderResolver {

         /**
          * Cached list of available providers cached by CacheKey to ensure
          * there is not potential for provider visibility issues.
          */
         private volatile HashMap<CacheKey, PersistenceProviderReference> providers = new HashMap<CacheKey, PersistenceProviderReference>();

         /**
          * Queue for reference objects referring to class loaders or persistence providers.
          */
         private static final ReferenceQueue referenceQueue = new ReferenceQueue();

         public List<PersistenceProvider> getPersistenceProviders() {
             // Before we do the real loading work, see whether we need to
             // do some cleanup: If references to class loaders or
             // persistence providers have been nulled out, remove all related
             // information from the cache.
             processQueue();

             ClassLoader loader = getContextClassLoader();
             CacheKey cacheKey = new CacheKey(loader);
             PersistenceProviderReference providersReferent = this.providers.get(cacheKey);
             List<PersistenceProvider> loadedProviders = null;

             if (providersReferent != null) {
                 loadedProviders = providersReferent.get();
             }

             if (loadedProviders == null) {
                 Collection<ProviderName> providerNames = getProviderNames(loader);
                 loadedProviders = new ArrayList<PersistenceProvider>();

                 for (ProviderName providerName : providerNames) {
                     try {
                         PersistenceProvider provider = (PersistenceProvider) loader.loadClass(providerName.getName()).newInstance();
                         loadedProviders.add(provider);
                     } catch (ClassNotFoundException cnfe) {
                         log(Level.FINEST, cnfe + ": " + providerName);
                     } catch (InstantiationException ie) {
                         log(Level.FINEST, ie + ": " + providerName);
                     } catch (IllegalAccessException iae) {
                         log(Level.FINEST, iae + ": " + providerName);
                     } catch (ClassCastException cce) {
                         log(Level.FINEST, cce + ": " + providerName);
                     }
                 }

                 // If none are found we'll log the provider names for diagnostic
                 // purposes.
                 if (loadedProviders.isEmpty() && !providerNames.isEmpty()) {
                     log(Level.WARNING, "No valid providers found using:");
                     for (ProviderName name : providerNames) {
                         log(Level.WARNING, name.toString());
                     }
                 }

                 providersReferent = new PersistenceProviderReference(loadedProviders, referenceQueue, cacheKey);

                 this.providers.put(cacheKey, providersReferent);
             }

             return loadedProviders;
         }

         /**
          * Remove garbage collected cache keys & providers.
          */
         private void processQueue() {
             CacheKeyReference ref;
             while ((ref = (CacheKeyReference) referenceQueue.poll()) != null) {
                 providers.remove(ref.getCacheKey());
             }
         }

         /**
          * Wraps <code>Thread.currentThread().getContextClassLoader()</code> into a doPrivileged block if security manager is present
          */
         private static ClassLoader getContextClassLoader() {
             if (System.getSecurityManager() == null) {
                 return Thread.currentThread().getContextClassLoader();
             }
             else {
                 return  (ClassLoader) java.security.AccessController.doPrivileged(
                         new java.security.PrivilegedAction() {
                             public java.lang.Object run() {
                                 return Thread.currentThread().getContextClassLoader();
                             }
                         }
                 );
             }
         }


         private static final String LOGGER_SUBSYSTEM = "javax.persistence.spi";

         private Logger logger;

         private void log(Level level, String message) {
             if (this.logger == null) {
                 this.logger = Logger.getLogger(LOGGER_SUBSYSTEM);
             }
             this.logger.log(level, LOGGER_SUBSYSTEM + "::" + message);
         }

         private static final String SERVICE_PROVIDER_FILE = "META-INF/services/javax.persistence.spi.PersistenceProvider";

         /**
          * Locate all JPA provider services files and collect all of the
          * provider names available.
          */
         private Collection<ProviderName> getProviderNames(ClassLoader loader) {
             Enumeration<URL> resources = null;

             try {
                 resources = loader.getResources(SERVICE_PROVIDER_FILE);
             } catch (IOException ioe) {
                 throw new PersistenceException("IOException caught: " + loader + ".getResources(" + SERVICE_PROVIDER_FILE + ")", ioe);
             }

             Collection<ProviderName> providerNames = new ArrayList<ProviderName>();

             while (resources.hasMoreElements()) {
                 URL url = resources.nextElement();
                 addProviderNames(url, providerNames);
             }

             return providerNames;
         }

         private static final Pattern nonCommentPattern = Pattern.compile("^([^#]+)");

         /**
          * For each services file look for uncommented provider names on each
          * line.
          */
         private void addProviderNames(URL url, Collection<ProviderName> providerNames) {
             InputStream in = null;
             try {
                 in = url.openStream();
                 BufferedReader reader = new BufferedReader(new InputStreamReader(in));

                 String line;
                 while ((line = reader.readLine()) != null) {
                     line = line.trim();
                     Matcher m = nonCommentPattern.matcher(line);
                     if (m.find()) {
                         providerNames.add(new ProviderName(m.group().trim(), url));
                     }
                 }
             } catch (IOException ioe) {
                 throw new PersistenceException("IOException caught reading: " + url, ioe);
             } finally {
                 if (in != null) {
                     try {
                         in.close();
                     } catch (IOException e) {
                     }
                 }
             }
         }

         /**
          * Clear all cached providers
          */
         public void clearCachedProviders() {
             this.providers.clear();
         }

         /**
          * A ProviderName captures each provider name found in a service file as
          * well as the URL for the service file it was found in. This
          * information is only used for diagnostic purposes.
          */
         private class ProviderName {

             /** Provider name **/
             private String name;

             /** URL for the service file where the provider name was found **/
             private URL source;

             public ProviderName(String name, URL sourceURL) {
                 this.name = name;
                 this.source = sourceURL;
             }

             public String getName() {
                 return name;
             }

             public URL getSource() {
                 return source;
             }

             public String toString() {
                 return getName() + " - " + getSource();
             }
         }

         /**
          * The common interface to get a CacheKey implemented by
          * LoaderReference and PersistenceProviderReference.
          */
         private interface CacheKeyReference {
             public CacheKey getCacheKey();
         }

         /**
           * Key used for cached persistence providers. The key checks
           * the class loader to determine if the persistence providers
           * is a match to the requested one. The loader may be null.
           */
         private class CacheKey implements Cloneable {

             /* Weak Reference to ClassLoader */
             private LoaderReference loaderRef;

             /* Cached Hashcode */
             private int hashCodeCache;

             CacheKey(ClassLoader loader) {
                 if (loader == null) {
                     this.loaderRef = null;
                 } else {
                     loaderRef = new LoaderReference(loader, referenceQueue, this);
                 }
                 calculateHashCode();
             }

             ClassLoader getLoader() {
                 return (loaderRef != null) ? loaderRef.get() : null;
             }

             public boolean equals(Object other) {
                 if (this == other) {
                     return true;
                 }
                 try {
                     final CacheKey otherEntry = (CacheKey) other;
                     // quick check to see if they are not equal
                     if (hashCodeCache != otherEntry.hashCodeCache) {
                         return false;
                     }
                     // are refs (both non-null) or (both null)?
                     if (loaderRef == null) {
                         return otherEntry.loaderRef == null;
                     }
                     ClassLoader loader = loaderRef.get();
                     return (otherEntry.loaderRef != null)
                     // with a null reference we can no longer find
                     // out which class loader was referenced; so
                     // treat it as unequal
                     && (loader != null) && (loader == otherEntry.loaderRef.get());
                 } catch (NullPointerException e) {
                 } catch (ClassCastException e) {
                 }

                 return false;
             }

             public int hashCode() {
                 return hashCodeCache;
             }

             private void calculateHashCode() {
                 ClassLoader loader = getLoader();
                 if (loader != null) {
                     hashCodeCache = loader.hashCode();
                 }
             }

             public Object clone() {
                 try {
                     CacheKey clone = (CacheKey) super.clone();
                     if (loaderRef != null) {
                         clone.loaderRef = new LoaderReference(loaderRef.get(), referenceQueue, clone);
                     }
                     return clone;
                 } catch (CloneNotSupportedException e) {
                     // this should never happen
                     throw new InternalError();
                 }
             }

             public String toString() {
                 return "CacheKey[" + getLoader() + ")]";
             }
         }

        /**
          * References to class loaders are weak references, so that they can be
          * garbage collected when nobody else is using them. The DefaultPersistenceProviderResolver
          * class has no reason to keep class loaders alive.
          */
         private class LoaderReference extends WeakReference<ClassLoader>
                 implements CacheKeyReference {
             private CacheKey cacheKey;

             LoaderReference(ClassLoader referent, ReferenceQueue q, CacheKey key) {
                 super(referent, q);
                 cacheKey = key;
             }

             public CacheKey getCacheKey() {
                 return cacheKey;
             }
         }

         /**
          * References to persistence provider are soft references so that they can be garbage
          * collected when they have no hard references.
          */
         private class PersistenceProviderReference extends SoftReference<List<PersistenceProvider>>
                 implements CacheKeyReference {
             private CacheKey cacheKey;

             PersistenceProviderReference(List<PersistenceProvider> referent, ReferenceQueue q, CacheKey key) {
                 super(referent, q);
                 cacheKey = key;
             }

             public CacheKey getCacheKey() {
                 return cacheKey;
             }
         }
     }
 }
	/*******************************************************************************
	* Copyright (c) 2008, 2009 Sun Microsystems. All rights reserved.
	*
	* This program and the accompanying materials are made available under the
	* terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
	* which accompanies this distribution.
	* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
	* and the Eclipse Distribution License is available at
	* http://www.eclipse.org/org/documents/edl-v10.php.
	*
	* Contributors:
	* Linda DeMichiel - Java Persistence 2.0 - Version 2.0 (October 1, 2009)
	* Specification available from http://jcp.org/en/jsr/detail?id=317
	* dclarke - EclipseLink implementation and default resolver
	*
	******************************************************************************/
	package javax.persistence.spi;

	import java.io.BufferedReader;
	import java.io.IOException;
	import java.io.InputStream;
	import java.io.InputStreamReader;
	import java.lang.ref.ReferenceQueue;
	import java.lang.ref.SoftReference;
	import java.lang.ref.WeakReference;
	import java.net.URL;
	import java.util.ArrayList;
	import java.util.Collection;
	import java.util.Enumeration;
	import java.util.List;
	import java.util.HashMap;
	import java.util.logging.Level;
	import java.util.logging.Logger;
	import java.util.regex.Matcher;
	import java.util.regex.Pattern;

	import javax.persistence.PersistenceException;

	/**
	* Holds the global {@link javax.persistence.spi.PersistenceProviderResolver}
	* instance. If no <code>PersistenceProviderResolver</code> is set by the
	* environment, the default </code>PersistenceProviderResolver is used.
	*
	* Implementations must be thread-safe.
	*
	* @since Java Persistence 2.0
	*/
	public class PersistenceProviderResolverHolder {

	private static PersistenceProviderResolver singleton = new DefaultPersistenceProviderResolver();

	/**
	* Returns the current persistence provider resolver.
	*
	* @return the current persistence provider resolver
	*/
	public static PersistenceProviderResolver getPersistenceProviderResolver() {
	return singleton;
	}

	/**
	* Defines the persistence provider resolver used.
	*
	* @param resolver persistence provider resolver to be used.
	*/
	public static void setPersistenceProviderResolver(PersistenceProviderResolver resolver) {
	if (resolver == null) {
	singleton = new DefaultPersistenceProviderResolver();
	} else {
	singleton = resolver;
	}
	}

	/**
	* Default provider resolver class to use when none is explicitly set.
	*
	* Uses the META-INF/services approach as described in the Java Persistence
	* specification. A getResources() call is made on the current context
	* classloader to find the service provider files on the classpath. Any
	* service files found are then read to obtain the classes that implement
	* the persistence provider interface.
	*/
	private static class DefaultPersistenceProviderResolver implements PersistenceProviderResolver {

	/**
	* Cached list of available providers cached by CacheKey to ensure
	* there is not potential for provider visibility issues.
	*/
	private volatile HashMap<CacheKey, PersistenceProviderReference> providers = new HashMap<CacheKey, PersistenceProviderReference>();

	/**
	* Queue for reference objects referring to class loaders or persistence providers.
	*/
	private static final ReferenceQueue referenceQueue = new ReferenceQueue();

	public List<PersistenceProvider> getPersistenceProviders() {
	// Before we do the real loading work, see whether we need to
	// do some cleanup: If references to class loaders or
	// persistence providers have been nulled out, remove all related
	// information from the cache.
	processQueue();

	ClassLoader loader = getContextClassLoader();
	CacheKey cacheKey = new CacheKey(loader);
	PersistenceProviderReference providersReferent = this.providers.get(cacheKey);
	List<PersistenceProvider> loadedProviders = null;

	if (providersReferent != null) {
	loadedProviders = providersReferent.get();
	}

	if (loadedProviders == null) {
	Collection<ProviderName> providerNames = getProviderNames(loader);
	loadedProviders = new ArrayList<PersistenceProvider>();

	for (ProviderName providerName : providerNames) {
	try {
	PersistenceProvider provider = (PersistenceProvider) loader.loadClass(providerName.getName()).newInstance();
	loadedProviders.add(provider);
	} catch (ClassNotFoundException cnfe) {
	log(Level.FINEST, cnfe + ": " + providerName);
	} catch (InstantiationException ie) {
	log(Level.FINEST, ie + ": " + providerName);
	} catch (IllegalAccessException iae) {
	log(Level.FINEST, iae + ": " + providerName);
	} catch (ClassCastException cce) {
	log(Level.FINEST, cce + ": " + providerName);
	}
	}

	// If none are found we'll log the provider names for diagnostic
	// purposes.
	if (loadedProviders.isEmpty() && !providerNames.isEmpty()) {
	log(Level.WARNING, "No valid providers found using:");
	for (ProviderName name : providerNames) {
	log(Level.WARNING, name.toString());
	}
	}

	providersReferent = new PersistenceProviderReference(loadedProviders, referenceQueue, cacheKey);

	this.providers.put(cacheKey, providersReferent);
	}

	return loadedProviders;
	}

	/**
	* Remove garbage collected cache keys & providers.
	*/
	private void processQueue() {
	CacheKeyReference ref;
	while ((ref = (CacheKeyReference) referenceQueue.poll()) != null) {
	providers.remove(ref.getCacheKey());
	}
	}

	/**
	* Wraps <code>Thread.currentThread().getContextClassLoader()</code> into a doPrivileged block if security manager is present
	*/
	private static ClassLoader getContextClassLoader() {
	if (System.getSecurityManager() == null) {
	return Thread.currentThread().getContextClassLoader();
	}
	else {
	return (ClassLoader) java.security.AccessController.doPrivileged(
	new java.security.PrivilegedAction() {
	public java.lang.Object run() {
	return Thread.currentThread().getContextClassLoader();
	}
	}
	);
	}
	}


	private static final String LOGGER_SUBSYSTEM = "javax.persistence.spi";

	private Logger logger;

	private void log(Level level, String message) {
	if (this.logger == null) {
	this.logger = Logger.getLogger(LOGGER_SUBSYSTEM);
	}
	this.logger.log(level, LOGGER_SUBSYSTEM + "::" + message);
	}

	private static final String SERVICE_PROVIDER_FILE = "META-INF/services/javax.persistence.spi.PersistenceProvider";

	/**
	* Locate all JPA provider services files and collect all of the
	* provider names available.
	*/
	private Collection<ProviderName> getProviderNames(ClassLoader loader) {
	Enumeration<URL> resources = null;

	try {
	resources = loader.getResources(SERVICE_PROVIDER_FILE);
	} catch (IOException ioe) {
	throw new PersistenceException("IOException caught: " + loader + ".getResources(" + SERVICE_PROVIDER_FILE + ")", ioe);
	}

	Collection<ProviderName> providerNames = new ArrayList<ProviderName>();

	while (resources.hasMoreElements()) {
	URL url = resources.nextElement();
	addProviderNames(url, providerNames);
	}

	return providerNames;
	}

	private static final Pattern nonCommentPattern = Pattern.compile("^([^#]+)");

	/**
	* For each services file look for uncommented provider names on each
	* line.
	*/
	private void addProviderNames(URL url, Collection<ProviderName> providerNames) {
	InputStream in = null;
	try {
	in = url.openStream();
	BufferedReader reader = new BufferedReader(new InputStreamReader(in));

	String line;
	while ((line = reader.readLine()) != null) {
	line = line.trim();
	Matcher m = nonCommentPattern.matcher(line);
	if (m.find()) {
	providerNames.add(new ProviderName(m.group().trim(), url));
	}
	}
	} catch (IOException ioe) {
	throw new PersistenceException("IOException caught reading: " + url, ioe);
	} finally {
	if (in != null) {
	try {
	in.close();
	} catch (IOException e) {
	}
	}
	}
	}

	/**
	* Clear all cached providers
	*/
	public void clearCachedProviders() {
	this.providers.clear();
	}

	/**
	* A ProviderName captures each provider name found in a service file as
	* well as the URL for the service file it was found in. This
	* information is only used for diagnostic purposes.
	*/
	private class ProviderName {

	/ Provider name /
	private String name;

	/ URL for the service file where the provider name was found /
	private URL source;

	public ProviderName(String name, URL sourceURL) {
	this.name = name;
	this.source = sourceURL;
	}

	public String getName() {
	return name;
	}

	public URL getSource() {
	return source;
	}

	public String toString() {
	return getName() + " - " + getSource();
	}
	}

	/**
	* The common interface to get a CacheKey implemented by
	* LoaderReference and PersistenceProviderReference.
	*/
	private interface CacheKeyReference {
	public CacheKey getCacheKey();
	}

	/**
	* Key used for cached persistence providers. The key checks
	* the class loader to determine if the persistence providers
	* is a match to the requested one. The loader may be null.
	*/
	private class CacheKey implements Cloneable {

	/* Weak Reference to ClassLoader */
	private LoaderReference loaderRef;

	/* Cached Hashcode */
	private int hashCodeCache;

	CacheKey(ClassLoader loader) {
	if (loader == null) {
	this.loaderRef = null;
	} else {
	loaderRef = new LoaderReference(loader, referenceQueue, this);
	}
	calculateHashCode();
	}

	ClassLoader getLoader() {
	return (loaderRef != null) ? loaderRef.get() : null;
	}

	public boolean equals(Object other) {
	if (this == other) {
	return true;
	}
	try {
	final CacheKey otherEntry = (CacheKey) other;
	// quick check to see if they are not equal
	if (hashCodeCache != otherEntry.hashCodeCache) {
	return false;
	}
	// are refs (both non-null) or (both null)?
	if (loaderRef == null) {
	return otherEntry.loaderRef == null;
	}
	ClassLoader loader = loaderRef.get();
	return (otherEntry.loaderRef != null)
	// with a null reference we can no longer find
	// out which class loader was referenced; so
	// treat it as unequal
	&& (loader != null) && (loader == otherEntry.loaderRef.get());
	} catch (NullPointerException e) {
	} catch (ClassCastException e) {
	}

	return false;
	}

	public int hashCode() {
	return hashCodeCache;
	}

	private void calculateHashCode() {
	ClassLoader loader = getLoader();
	if (loader != null) {
	hashCodeCache = loader.hashCode();
	}
	}

	public Object clone() {
	try {
	CacheKey clone = (CacheKey) super.clone();
	if (loaderRef != null) {
	clone.loaderRef = new LoaderReference(loaderRef.get(), referenceQueue, clone);
	}
	return clone;
	} catch (CloneNotSupportedException e) {
	// this should never happen
	throw new InternalError();
	}
	}

	public String toString() {
	return "CacheKey[" + getLoader() + ")]";
	}
	}

	/**
	* References to class loaders are weak references, so that they can be
	* garbage collected when nobody else is using them. The DefaultPersistenceProviderResolver
	* class has no reason to keep class loaders alive.
	*/
	private class LoaderReference extends WeakReference<ClassLoader>
	implements CacheKeyReference {
	private CacheKey cacheKey;

	LoaderReference(ClassLoader referent, ReferenceQueue q, CacheKey key) {
	super(referent, q);
	cacheKey = key;
	}

	public CacheKey getCacheKey() {
	return cacheKey;
	}
	}

	/**
	* References to persistence provider are soft references so that they can be garbage
	* collected when they have no hard references.
	*/
	private class PersistenceProviderReference extends SoftReference<List<PersistenceProvider>>
	implements CacheKeyReference {
	private CacheKey cacheKey;

	PersistenceProviderReference(List<PersistenceProvider> referent, ReferenceQueue q, CacheKey key) {
	super(referent, q);
	cacheKey = key;
	}

	public CacheKey getCacheKey() {
	return cacheKey;
	}
	}
	}
	}