Java tutorial
/******************************************************************************* * This file is part of OpenNMS(R). * * Copyright (C) 2012 The OpenNMS Group, Inc. * OpenNMS(R) is Copyright (C) 1999-2012 The OpenNMS Group, Inc. * * OpenNMS(R) is a registered trademark of The OpenNMS Group, Inc. * * OpenNMS(R) is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published * by the Free Software Foundation, either version 3 of the License, * or (at your option) any later version. * * OpenNMS(R) is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with OpenNMS(R). If not, see: * http://www.gnu.org/licenses/ * * For more information contact: * OpenNMS(R) Licensing <license@opennms.org> * http://www.opennms.org/ * http://www.opennms.com/ *******************************************************************************/ package com.netxforge.oss2.config; import java.io.File; import java.io.FileInputStream; import java.io.IOException; import java.io.InputStream; import java.util.ArrayList; import java.util.HashSet; import java.util.List; import java.util.Map; import java.util.Set; import java.util.concurrent.ConcurrentHashMap; import java.util.concurrent.locks.Lock; import java.util.concurrent.locks.ReadWriteLock; import java.util.concurrent.locks.ReentrantReadWriteLock; import org.apache.commons.io.IOUtils; import org.exolab.castor.xml.MarshalException; import org.exolab.castor.xml.ValidationException; import org.opennms.core.utils.ConfigFileConstants; import org.opennms.core.xml.CastorUtils; import org.opennms.netmgt.config.filter.Column; import org.opennms.netmgt.config.filter.DatabaseSchema; import org.opennms.netmgt.config.filter.Join; import org.opennms.netmgt.config.filter.Table; /** * This is the singleton class used to load the configuration for the OpenNMS * database schema for the filters from the database-schema XML file. * * <strong>Note: </strong>Users of this class should make sure the * <em>init()</em> is called before calling any other method to ensure the * config is loaded before accessing other convenience methods. * * @author <a href="mailto:sowmya@opennms.org">Sowmya Nataraj </a> */ public final class DatabaseSchemaConfigFactory { private final ReadWriteLock m_globalLock = new ReentrantReadWriteLock(); private final Lock m_readLock = m_globalLock.readLock(); private final Lock m_writeLock = m_globalLock.writeLock(); /** * The singleton instance of this factory */ private static DatabaseSchemaConfigFactory m_singleton = null; /** * The config class loaded from the config file */ private DatabaseSchema m_config; /** * The set of tables that can be joined directly or indirectly to the * primary table */ // FIXME: m_joinable is never read //private Set m_joinable = null; /** * A map from a table to the join to use to get 'closer' to the primary * table */ private Map<String, Join> m_primaryJoins = null; /** * This member is set to true if the configuration file has been loaded. */ private static boolean m_loaded = false; /** * Private constructor * @throws ValidationException * @throws MarshalException * * @exception java.io.IOException * Thrown if the specified config file cannot be read * @exception org.exolab.castor.xml.MarshalException * Thrown if the file does not conform to the schema. * @exception org.exolab.castor.xml.ValidationException * Thrown if the contents do not match the required schema. */ private DatabaseSchemaConfigFactory(final String configFile) throws IOException, MarshalException, ValidationException { InputStream cfgStream = null; try { cfgStream = new FileInputStream(configFile); m_config = CastorUtils.unmarshal(DatabaseSchema.class, cfgStream); finishConstruction(); } finally { IOUtils.closeQuietly(cfgStream); } } /** * <p>Constructor for DatabaseSchemaConfigFactory.</p> * * @param is a {@link java.io.InputStream} object. * @throws org.exolab.castor.xml.MarshalException if any. * @throws org.exolab.castor.xml.ValidationException if any. */ public DatabaseSchemaConfigFactory(final InputStream is) throws MarshalException, ValidationException { m_config = CastorUtils.unmarshal(DatabaseSchema.class, is); finishConstruction(); } public Lock getReadLock() { return m_readLock; } public Lock getWriteLock() { return m_writeLock; } /** * Load the config from the default config file and create the singleton * instance of this factory. * * @exception java.io.IOException * Thrown if the specified config file cannot be read * @exception org.exolab.castor.xml.MarshalException * Thrown if the file does not conform to the schema. * @exception org.exolab.castor.xml.ValidationException * Thrown if the contents do not match the required schema. * @throws java.io.IOException if any. * @throws org.exolab.castor.xml.MarshalException if any. * @throws org.exolab.castor.xml.ValidationException if any. */ public static synchronized void init() throws IOException, MarshalException, ValidationException { if (m_loaded) { // init already called - return // to reload, reload() will need to be called return; } final File cfgFile = ConfigFileConstants.getFile(ConfigFileConstants.DB_SCHEMA_FILE_NAME); m_singleton = new DatabaseSchemaConfigFactory(cfgFile.getPath()); m_loaded = true; } /** * Reload the config from the default config file * * @exception java.io.IOException * Thrown if the specified config file cannot be read/loaded * @exception org.exolab.castor.xml.MarshalException * Thrown if the file does not conform to the schema. * @exception org.exolab.castor.xml.ValidationException * Thrown if the contents do not match the required schema. * @throws java.io.IOException if any. * @throws org.exolab.castor.xml.MarshalException if any. * @throws org.exolab.castor.xml.ValidationException if any. */ public static synchronized void reload() throws IOException, MarshalException, ValidationException { m_singleton = null; m_loaded = false; init(); } /** * Return the singleton instance of this factory. * * @return The current factory instance. * @throws java.lang.IllegalStateException * Thrown if the factory has not yet been initialized. */ public static synchronized DatabaseSchemaConfigFactory getInstance() { if (!m_loaded) throw new IllegalStateException("The factory has not been initialized"); return m_singleton; } /** * <p>setInstance</p> * * @param instance a {@link org.opennms.netmgt.config.DatabaseSchemaConfigFactory} object. */ public static synchronized void setInstance(final DatabaseSchemaConfigFactory instance) { m_singleton = instance; m_loaded = true; } /** * Return the database schema. * * @return the database schema */ public DatabaseSchema getDatabaseSchema() { final Lock lock = getReadLock(); lock.lock(); try { return m_config; } finally { lock.unlock(); } } /** * This method is used to find the table that should drive the construction * of the join clauses between all table in the from clause. At least one * table has to be designated as the driver table. * * @return The name of the driver table */ public Table getPrimaryTable() { getReadLock().lock(); try { for (final Table t : getDatabaseSchema().getTableCollection()) { if (t.getVisible() == null || t.getVisible().equalsIgnoreCase("true")) { if (t.getKey() != null && t.getKey().equals("primary")) { return t; } } } return null; } finally { getReadLock().unlock(); } } /** * Construct m_primaryJoins */ private void finishConstruction() { Set<String> joinableSet = new HashSet<String>(); final Map<String, Join> primaryJoins = new ConcurrentHashMap<String, Join>(); joinableSet.add(getPrimaryTable().getName()); // loop until we stop adding entries to the set int joinableCount = 0; while (joinableCount < joinableSet.size()) { joinableCount = joinableSet.size(); final Set<String> newSet = new HashSet<String>(joinableSet); for (final Table t : getDatabaseSchema().getTableCollection()) { if (!joinableSet.contains(t.getName()) && (t.getVisible() == null || t.getVisible().equalsIgnoreCase("true"))) { for (final Join j : t.getJoinCollection()) { if (joinableSet.contains(j.getTable())) { newSet.add(t.getName()); primaryJoins.put(t.getName(), j); } } } } joinableSet = newSet; } m_primaryJoins = primaryJoins; } /** * Find a table using its name as the search key. * * @param name * the name of the table to find * @return the table if it is found, null otherwise. */ public Table getTableByName(final String name) { getReadLock().lock(); try { for (final Table t : getDatabaseSchema().getTableCollection()) { if (t.getVisible() == null || t.getVisible().equalsIgnoreCase("true")) { if (t.getName() != null && t.getName().equals(name)) { return t; } } } return null; } finally { getReadLock().unlock(); } } /** * Find the table which has a visible column named 'colName' * * @return the table containing column 'colName', null if colName is not a * valid column or if is not visible. * @param colName a {@link java.lang.String} object. */ public Table findTableByVisibleColumn(final String colName) { Table table = null; getReadLock().lock(); try { OUTER: for (final Table t : getDatabaseSchema().getTableCollection()) { for (final Column col : t.getColumnCollection()) { if (col.getVisible() == null || col.getVisible().equalsIgnoreCase("true")) { if (col.getName().equalsIgnoreCase(colName)) { table = t; break OUTER; } } } } return table; } finally { getReadLock().unlock(); } } /** * Return a count of the number of tables defined. * * @return the number of tables in the schema */ public int getTableCount() { final Lock lock = getReadLock(); lock.lock(); try { return getDatabaseSchema().getTableCount(); } finally { lock.unlock(); } } /** * Return the sequence of tables necessary to join the primary table to the * given tables. * * @param tables * list of Tables to join * @return a list of table names, starting with the primary table, going * to each of the given tables, or a zero-length array if no join * exists or only the primary table was specified */ public List<String> getJoinTables(final List<Table> tables) { final List<String> joinedTables = new ArrayList<String>(); getReadLock().lock(); try { for (int i = 0; i < tables.size(); i++) { final int insertPosition = joinedTables.size(); String currentTable = tables.get(i).getName(); while (currentTable != null && !joinedTables.contains(currentTable)) { joinedTables.add(insertPosition, currentTable); final Join next = m_primaryJoins.get(currentTable); if (next != null) { currentTable = next.getTable(); } else { currentTable = null; } } } return joinedTables; } finally { getReadLock().unlock(); } } /** * Construct a SQL FROM clause joining the given tables to the primary table. * * @param tables * list of Tables to join * @return an SQL FROM clause or "" if no expression is found */ public String constructJoinExprForTables(final List<Table> tables) { StringBuffer joinExpr = new StringBuffer(); getReadLock().lock(); try { final List<String> joinTables = getJoinTables(tables); joinExpr.append(joinTables.get(0)); for (int i = 1; i < joinTables.size(); i++) { final Join currentJoin = m_primaryJoins.get(joinTables.get(i)); if (currentJoin.getType() != null && !currentJoin.getType().equalsIgnoreCase("inner")) { joinExpr.append(" " + currentJoin.getType().toUpperCase()); } joinExpr.append(" JOIN " + joinTables.get(i) + " ON ("); joinExpr.append(currentJoin.getTable() + "." + currentJoin.getTableColumn() + " = "); joinExpr.append(joinTables.get(i) + "." + currentJoin.getColumn() + ")"); } if (joinExpr.length() > 0) return "FROM " + joinExpr.toString(); return ""; } finally { getReadLock().unlock(); } } }