001/* 002 * HA-JDBC: High-Availability JDBC 003 * Copyright (c) 2004-2008 Paul Ferraro 004 * 005 * This library is free software; you can redistribute it and/or modify it 006 * under the terms of the GNU Lesser General Public License as published by the 007 * Free Software Foundation; either version 2.1 of the License, or (at your 008 * option) any later version. 009 * 010 * This library is distributed in the hope that it will be useful, but WITHOUT 011 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 012 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License 013 * for more details. 014 * 015 * You should have received a copy of the GNU Lesser General Public License 016 * along with this library; if not, write to the Free Software Foundation, 017 * Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 018 * 019 * Contact: ferraro@users.sourceforge.net 020 */ 021package net.sf.hajdbc.sql; 022 023import java.util.List; 024import java.util.concurrent.locks.Lock; 025 026/** 027 * An invocation strategy decorator that acquires a list of locks before invocation, and releases them afterward. 028 * @author Paul Ferraro 029 * @param <D> Type of the root object (e.g. driver, datasource) 030 * @param <T> Target object type of the invocation 031 * @param <R> Return type of this invocation 032 */ 033public class LockingInvocationStrategy<D, T, R> implements InvocationStrategy<D, T, R> 034{ 035 private InvocationStrategy<D, T, R> strategy; 036 private List<Lock> lockList; 037 038 /** 039 * @param strategy 040 * @param lockList 041 */ 042 public LockingInvocationStrategy(InvocationStrategy<D, T, R> strategy, List<Lock> lockList) 043 { 044 this.strategy = strategy; 045 this.lockList = lockList; 046 } 047 048 /** 049 * @see net.sf.hajdbc.sql.InvocationStrategy#invoke(net.sf.hajdbc.sql.SQLProxy, net.sf.hajdbc.sql.Invoker) 050 */ 051 @Override 052 public R invoke(SQLProxy<D, T> proxy, Invoker<D, T, R> invoker) throws Exception 053 { 054 for (Lock lock: this.lockList) 055 { 056 lock.lock(); 057 } 058 059 try 060 { 061 return this.strategy.invoke(proxy, invoker); 062 } 063 finally 064 { 065 for (Lock lock: this.lockList) 066 { 067 lock.unlock(); 068 } 069 } 070 } 071}