001/* 002 * HA-JDBC: High-Availability JDBC 003 * Copyright (c) 2004-2007 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; 022 023import java.util.Set; 024 025/** 026 * @author Paul Ferraro 027 * @since 1.0 028 * @param <D> either java.sql.Driver or javax.sql.DataSource 029 */ 030public interface Balancer<D> 031{ 032 /** 033 * Removes the specified database from this balancer. 034 * @param database a database descriptor 035 * @return true, if the database was removed successfully, false if it did not exist. 036 */ 037 public boolean remove(Database<D> database); 038 039 /** 040 * Adds the specified database to this balancer. 041 * @param database a database descriptor 042 * @return true, if the database was added successfully, false if already existed. 043 */ 044 public boolean add(Database<D> database); 045 046 /** 047 * Returns the next database from this balancer 048 * @return the next database from this balancer 049 */ 050 public Database<D> next(); 051 052 /** 053 * Returns an unmodifiable collection of databases known to this balancer 054 * @return a collection of database descriptors 055 */ 056 public Set<Database<D>> all(); 057 058 /** 059 * Called before an operation is performed on the specified database retrieved via {@link #next()}. 060 * @param database a database descriptor 061 */ 062 public void beforeInvocation(Database<D> database); 063 064 /** 065 * Called after an operation is performed on the specified database retrieved via {@link #next()}. 066 * @param database a database descriptor 067 */ 068 public void afterInvocation(Database<D> database); 069 070 /** 071 * Removes all databases from this balancer. 072 */ 073 public void clear(); 074}