sqlclauseiterator.java

Mandarax是一个规则引擎的纯Java实现。它支持多类型的事实和基于反映的规则

/*
 * Copyright (C) 1999-2004 <A href="http://www-ist.massey.ac.nz/JBDietrich" target="_top">Jens Dietrich</a>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
package org.mandarax.sql;

import java.sql.Connection;
import java.sql.SQLException;
import java.util.List;
import java.util.Map;
import org.mandarax.util.logging.LogCategories;
import org.mandarax.kernel.Clause;
import org.mandarax.kernel.ClauseSetException;
import org.mandarax.kernel.Fact;
import org.mandarax.kernel.LogicFactory;
import org.mandarax.kernel.Term;

/**
 * Clause set iterator for SQL clause sets.
 * @author <A href="http://www-ist.massey.ac.nz/JBDietrich" target="_top">Jens Dietrich</A>
 * @version 3.4 <7 March 05>
 * @since 1.5
 */
class SQLClauseIterator extends org.mandarax.util.AbstractClauseIterator implements LogCategories {

	private SQLPredicate predicate;
	private java.sql.ResultSet rs = null;
	private Fact nextFact = null;
	private LogicFactory logFact = LogicFactory.getDefaultFactory();
	private Class[] struct = null;
	private SQLTypeMapping typeMapping = null;
	private Map map = null;
	private List cache = null;
	private boolean closeConnection = false;
	private Connection connection = null;

	/**
	 * Constructor.
	 * @param p the predicate
	 * @param queryResult the result set
	 * @param c the cache list to collect facts - if null, nothing will be cached
	 * @param closeConnection whether to close the connection at the end
	 * @param con the connection used
	 */
	SQLClauseIterator(SQLPredicate p, java.sql.ResultSet queryResult, List c, boolean closeConnection,Connection con) {
		super();
		predicate = p;
		rs = queryResult;
		struct = predicate.getStructure();
		typeMapping = predicate.getTypeMapping();
		map = (typeMapping == null) ? null : typeMapping.getTypeMapping();
		cache = c;
		this.closeConnection = closeConnection;
		this.connection = con;
	}
	
	/**
	 * Indicates whether there are more clauses.
	 * @return true if there are more clauses, false otherwise
	 * @throws ClauseSetException
	 */
	public boolean hasMoreClauses() throws ClauseSetException {
		try {
			boolean hasNext = rs.next();
			if (hasNext) {
				Term[] terms = new Term[struct.length];
				for (int i = 0; i < struct.length; i++) {
					if (typeMapping == null) {
						terms[i] = logFact.createConstantTerm(rs.getObject(i + 1));
					}
					else {
						terms[i] = logFact.createConstantTerm(typeMapping.postMap((map==null)?rs.getObject(i+1):rs.getObject(i+1,map)));
					}
				}
				nextFact = logFact.createFact(predicate, terms);
				if (cache != null) {
					cache.add(nextFact);
				}
				return true;
			}
			else {
				nextFact = null;
				return false;
			}
		}
		catch (SQLException x) {
			nextFact = null;
			throw new ClauseSetException("Exception building facts from records",x);
		}
	}

	/**
	 * Get the next clause.
	 * @return the next clause
	 * @throws ClauseSetException
	 */
	public Clause nextClause() throws ClauseSetException {
		return nextFact;
	}

	/**
     * Close the iterator and release all resources.
     */
    public void close() {
    	try {
    		if (rs!=null && closeConnection) {
    			rs.close();
    			if (LOG_SQL.isDebugEnabled()) LOG_SQL.debug("JDBC connection released by SQLClauseIterator " + this);	
    		}
    	}
    	catch (SQLException x) {
    		LOG_SQL.error("Exception closing result set in SQL clause iterator",x);
    	}
     	try {
    		if (connection!=null && closeConnection) connection.close();
    	}
    	catch (SQLException x) {
    		LOG_SQL.error("Exception closing connection in SQL clause iterator",x);
    	}   	
    }
}