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/**
* Copyright (C) 2006-2014 phloc systems
* http://www.phloc.com
* office[at]phloc[dot]com
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.phloc.commons.lang;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.ServiceLoader;
import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import javax.annotation.concurrent.Immutable;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import com.phloc.commons.GlobalDebug;
import com.phloc.commons.ValueEnforcer;
import com.phloc.commons.annotations.ReturnsMutableCopy;
/**
* {@link ServiceLoader} helper class.
*
* @author boris
* @author Philip Helger
*/
// IFJDK5
// @SuppressWarnings ("javadoc")
// ELSE
// ENDIF
@Immutable
public final class ServiceLoaderUtils
{
private static final Logger s_aLogger = LoggerFactory.getLogger (ServiceLoaderUtils.class);
private ServiceLoaderUtils ()
{}
@Nonnull
private static ClassLoader _getDefaultClassLoader ()
{
return ClassHelper.getDefaultClassLoader ();
}
/**
* Uses the {@link ServiceLoader} to load all SPI implementations of the
* passed class
*
* @param aSPIClass
* The SPI interface class. May not be null.
* @return A list of all currently available plugins
*/
@Nonnull
@ReturnsMutableCopy
public static List getAllSPIImplementations (@Nonnull final Class aSPIClass)
{
return getAllSPIImplementations (aSPIClass, _getDefaultClassLoader (), null);
}
/**
* Uses the {@link ServiceLoader} to load all SPI implementations of the
* passed class
*
* @param aSPIClass
* The SPI interface class. May not be null.
* @param aClassLoader
* The class loader to use for the SPI loader. May not be
* null.
* @return A list of all currently available plugins
*/
@Nonnull
@ReturnsMutableCopy
public static List getAllSPIImplementations (@Nonnull final Class aSPIClass,
@Nonnull final ClassLoader aClassLoader)
{
return getAllSPIImplementations (aSPIClass, aClassLoader, null);
}
/**
* Uses the {@link ServiceLoader} to load all SPI implementations of the
* passed class
*
* @param aSPIClass
* The SPI interface class. May not be null.
* @param aLogger
* An optional logger to use. May be null.
* @return A list of all currently available plugins
*/
@Nonnull
@ReturnsMutableCopy
public static List getAllSPIImplementations (@Nonnull final Class aSPIClass,
@Nullable final Logger aLogger)
{
return getAllSPIImplementations (aSPIClass, _getDefaultClassLoader (), aLogger);
}
/**
* Uses the {@link ServiceLoader} to load all SPI implementations of the
* passed class
*
* @param aSPIClass
* The SPI interface class. May not be null.
* @param aClassLoader
* The class loader to use for the SPI loader. May not be
* null.
* @param aLogger
* An optional logger to use. May be null.
* @return A collection of all currently available plugins. Never
* null.
*/
@Nonnull
@ReturnsMutableCopy
public static List getAllSPIImplementations (@Nonnull final Class aSPIClass,
@Nonnull final ClassLoader aClassLoader,
@Nullable final Logger aLogger)
{
ValueEnforcer.notNull (aSPIClass, "SPIClass");
ValueEnforcer.notNull (aClassLoader, "ClassLoader");
final Logger aRealLogger = aLogger != null ? aLogger : s_aLogger;
if (aRealLogger.isDebugEnabled ())
aRealLogger.debug ("Trying to load all SPI implementations of " + aSPIClass);
// IFJDK5
// final ServiceLoaderBackport aServiceLoader =
// ServiceLoaderBackport. load (aSPIClass, aClassLoader);
// ELSE
final ServiceLoader aServiceLoader = ServiceLoader. load (aSPIClass, aClassLoader);
// ENDIF
final List ret = new ArrayList ();
// We use the iterator to be able to catch exceptions thrown
// when loading SPI implementations (e.g. the SPI implementation class does
// not exist)
final Iterator aIterator = aServiceLoader.iterator ();
while (aIterator.hasNext ())
{
try
{
ret.add (aIterator.next ());
}
catch (final Throwable t)
{
aRealLogger.error ("Unable to load an SPI implementation of " + aSPIClass, t);
}
}
if (aRealLogger.isDebugEnabled () || GlobalDebug.isDebugMode ())
{
final String sMessage = "Finished loading all SPI implementations of " +
aSPIClass +
" --> returning " +
ret.size () +
" instances";
if (aRealLogger.isDebugEnabled ())
aRealLogger.debug (sMessage);
else
aRealLogger.info (sMessage);
}
return ret;
}
/**
* Uses the {@link ServiceLoader} to load all SPI implementations of the
* passed class and return only the first instance.
*
* @param aSPIClass
* The SPI interface class. May not be null.
* @return A collection of all currently available plugins. Never
* null.
*/
@Nullable
public static T getFirstSPIImplementation (@Nonnull final Class aSPIClass)
{
return getFirstSPIImplementation (aSPIClass, _getDefaultClassLoader (), null);
}
/**
* Uses the {@link ServiceLoader} to load all SPI implementations of the
* passed class and return only the first instance.
*
* @param aSPIClass
* The SPI interface class. May not be null.
* @param aClassLoader
* The class loader to use for the SPI loader. May not be
* null.
* @return A collection of all currently available plugins. Never
* null.
*/
@Nullable
public static T getFirstSPIImplementation (@Nonnull final Class aSPIClass,
@Nonnull final ClassLoader aClassLoader)
{
return getFirstSPIImplementation (aSPIClass, aClassLoader, null);
}
/**
* Uses the {@link ServiceLoader} to load all SPI implementations of the
* passed class and return only the first instance.
*
* @param aSPIClass
* The SPI interface class. May not be null.
* @param aLogger
* An optional logger to use. May be null.
* @return A collection of all currently available plugins. Never
* null.
*/
@Nullable
public static T getFirstSPIImplementation (@Nonnull final Class aSPIClass, @Nullable final Logger aLogger)
{
return getFirstSPIImplementation (aSPIClass, _getDefaultClassLoader (), aLogger);
}
/**
* Uses the {@link ServiceLoader} to load all SPI implementations of the
* passed class and return only the first instance.
*
* @param aSPIClass
* The SPI interface class. May not be null.
* @param aClassLoader
* The class loader to use for the SPI loader. May not be
* null.
* @param aLogger
* An optional logger to use. May be null.
* @return A collection of all currently available plugins. Never
* null.
*/
@Nullable
public static T getFirstSPIImplementation (@Nonnull final Class aSPIClass,
@Nonnull final ClassLoader aClassLoader,
@Nullable final Logger aLogger)
{
final Logger aRealLogger = aLogger != null ? aLogger : s_aLogger;
final List aAll = getAllSPIImplementations (aSPIClass, aClassLoader, aRealLogger);
if (aAll.isEmpty ())
{
// No SPI implementation found
return null;
}
if (aAll.size () > 1)
{
// More than one implementation found
aRealLogger.warn ("Requested only one SPI implementation of " +
aSPIClass +
" but found " +
aAll.size () +
": " +
aAll);
}
return aAll.get (0);
}
}
