Java tutorial
/** * The software subject to this notice and license includes both human readable * source code form and machine readable, binary, object code form. The nci-commons * Software was developed in conjunction with the National Cancer Institute * (NCI) by NCI employees and 5AM Solutions, Inc. (5AM). To the extent * government employees are authors, any rights in such works shall be subject * to Title 17 of the United States Code, section 105. * * This nci-commons Software License (the License) is between NCI and You. You (or * Your) shall mean a person or an entity, and all other entities that control, * are controlled by, or are under common control with the entity. Control for * purposes of this definition means (i) the direct or indirect power to cause * the direction or management of such entity, whether by contract or otherwise, * or (ii) ownership of fifty percent (50%) or more of the outstanding shares, * or (iii) beneficial ownership of such entity. * * This License is granted provided that You agree to the conditions described * below. NCI grants You a non-exclusive, worldwide, perpetual, fully-paid-up, * no-charge, irrevocable, transferable and royalty-free right and license in * its rights in the nci-commons Software to (i) use, install, access, operate, * execute, copy, modify, translate, market, publicly display, publicly perform, * and prepare derivative works of the nci-commons Software; (ii) distribute and * have distributed to and by third parties the nci-commons Software and any * modifications and derivative works thereof; and (iii) sublicense the * foregoing rights set out in (i) and (ii) to third parties, including the * right to license such rights to further third parties. For sake of clarity, * and not by way of limitation, NCI shall have no right of accounting or right * of payment from You or Your sub-licensees for the rights granted under this * License. This License is granted at no charge to You. * * Your redistributions of the source code for the Software must retain the * above copyright notice, this list of conditions and the disclaimer and * limitation of liability of Article 6, below. Your redistributions in object * code form must reproduce the above copyright notice, this list of conditions * and the disclaimer of Article 6 in the documentation and/or other materials * provided with the distribution, if any. * * Your end-user documentation included with the redistribution, if any, must * include the following acknowledgment: This product includes software * developed by 5AM and the National Cancer Institute. If You do not include * such end-user documentation, You shall include this acknowledgment in the * Software itself, wherever such third-party acknowledgments normally appear. * * You may not use the names "The National Cancer Institute", "NCI", or "5AM" * to endorse or promote products derived from this Software. This License does * not authorize You to use any trademarks, service marks, trade names, logos or * product names of either NCI or 5AM, except as required to comply with the * terms of this License. * * For sake of clarity, and not by way of limitation, You may incorporate this * Software into Your proprietary programs and into any third party proprietary * programs. However, if You incorporate the Software into third party * proprietary programs, You agree that You are solely responsible for obtaining * any permission from such third parties required to incorporate the Software * into such third party proprietary programs and for informing Your * sub-licensees, including without limitation Your end-users, of their * obligation to secure any required permissions from such third parties before * incorporating the Software into such third party proprietary software * programs. In the event that You fail to obtain such permissions, You agree * to indemnify NCI for any claims against NCI by such third parties, except to * the extent prohibited by law, resulting from Your failure to obtain such * permissions. * * For sake of clarity, and not by way of limitation, You may add Your own * copyright statement to Your modifications and to the derivative works, and * You may provide additional or different license terms and conditions in Your * sublicenses of modifications of the Software, or any derivative works of the * Software as a whole, provided Your use, reproduction, and distribution of the * Work otherwise complies with the conditions stated in this License. * * THIS SOFTWARE IS PROVIDED "AS IS," AND ANY EXPRESSED OR IMPLIED WARRANTIES, * (INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY, * NON-INFRINGEMENT AND FITNESS FOR A PARTICULAR PURPOSE) ARE DISCLAIMED. IN NO * EVENT SHALL THE NATIONAL CANCER INSTITUTE, 5AM SOLUTIONS, INC. OR THEIR * AFFILIATES BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ package gov.nih.nci.firebird.proxy; import com.google.inject.Provider; import java.lang.reflect.InvocationHandler; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.util.List; import java.util.ArrayList; import org.apache.commons.pool.BasePoolableObjectFactory; import org.apache.commons.pool.ObjectPool; import org.apache.commons.pool.PoolableObjectFactory; import org.apache.commons.pool.impl.StackObjectPool; import org.apache.log4j.Logger; /** * Handler to be used by a dynamic proxy that will borrow the delegate-client from a pool. */ class PoolingHandler implements InvocationHandler { private static final Logger LOG = Logger.getLogger(PoolingHandler.class); private ObjectPool<Object> pool; private List<Class<? extends Throwable>> validExceptions = new ArrayList<Class<? extends Throwable>>(0); /** * @param pool the pool to borrow from. */ public PoolingHandler(ObjectPool<Object> pool) { this.pool = pool; } /** * use a StackObjectPool. * @param factory - the PoolableObjectFactory used to populate the pool * @param maxIdle - cap on the number of "sleeping" instances in the pool * @param initIdleCapacity - initial size of the pool (this specifies the size of the container, * it does not cause the pool to be pre-populated.) */ public PoolingHandler(PoolableObjectFactory<Object> factory, int maxIdle, int initIdleCapacity) { this(new StackObjectPool<Object>(factory, maxIdle, initIdleCapacity)); } /** * use a StackObjectPool. * @param provider - the Provider used to populate the pool * @param maxIdle - cap on the number of "sleeping" instances in the pool * @param initIdleCapacity - initial size of the pool (this specifies the size of the container, * it does not cause the pool to be pre-populated.) */ @SuppressWarnings("ucd") // convenience constructor used in tests public PoolingHandler(Provider<?> provider, int maxIdle, int initIdleCapacity) { this(new ProviderObjectFactory(provider), maxIdle, initIdleCapacity); } /** * @return types of exceptions that will NOT evict delegate-clients from the pool. */ public List<Class<? extends Throwable>> getValidExceptions() { return validExceptions; } /** * @param validExceptions types of exceptions that will NOT evict delegate-clients from the pool. */ public void setValidExceptions(List<Class<? extends Throwable>> validExceptions) { this.validExceptions = validExceptions; } /** * @return the client pool. */ public ObjectPool<Object> getPool() { return pool; } @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { return invoke(method, args); } private Object invoke(Method method, Object[] args) throws Throwable { Object client = pool.borrowObject(); try { Object ret = method.invoke(client, args); pool.returnObject(client); return ret; } catch (InvocationTargetException t) { if (isValidException(t.getTargetException())) { pool.returnObject(client); } else { pool.invalidateObject(client); LOG.error("invalidated delegate due to an unexpected exception", t.getTargetException()); } throw t.getTargetException(); } } private boolean isValidException(Throwable t) { for (Class<? extends Throwable> validExceptionType : getValidExceptions()) { if (validExceptionType.isAssignableFrom(t.getClass())) { return true; } } return false; } /** * PoolableObjectFactory wrapper for a provider. */ public static class ProviderObjectFactory extends BasePoolableObjectFactory<Object> { private final Provider<?> provider; /** * @param provider the provider to wrap. */ public ProviderObjectFactory(Provider<?> provider) { this.provider = provider; } @Override public Object makeObject() { return provider.get(); } } }