jdbc/src/main/java/org/apache/metamodel/jdbc/JdbcCompiledQuery.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.metamodel.jdbc;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.util.List;

import org.apache.commons.pool.impl.GenericObjectPool;
import org.apache.metamodel.MetaModelException;
import org.apache.metamodel.query.CompiledQuery;
import org.apache.metamodel.query.DefaultCompiledQuery;
import org.apache.metamodel.query.Query;
import org.apache.metamodel.query.SelectItem;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Implementation of {@link CompiledQuery} for JDBC which uses a
 * {@link PreparedStatement} behind the scenes.
 */
final class JdbcCompiledQuery extends DefaultCompiledQuery implements CompiledQuery {

	private static final Logger logger = LoggerFactory.getLogger(JdbcCompiledQuery.class);

	private final JdbcDataContext _dataContext;
	private final Connection _connection;
	private final String _sql;
	private final Query _query;
	private final GenericObjectPool<JdbcCompiledQueryLease> _pool;
	private boolean _closed;

	public JdbcCompiledQuery(JdbcDataContext dc, Query query) {
		super(query);
		_dataContext = dc;
		_connection = dc.getConnection();
		_query = query;
		_sql = dc.getQueryRewriter().rewriteQuery(query);
		_pool = new GenericObjectPool<JdbcCompiledQueryLease>(new JdbcCompiledQueryLeaseFactory(dc, _connection, _sql));
		_closed = false;

		logger.debug("Created compiled JDBC query: {}", _sql);
	}

	public JdbcCompiledQueryLease borrowLease() {
		if (logger.isDebugEnabled()) {
			logger.debug("Borrowing lease. Leases (before): Active={}, Idle={}", getActiveLeases(), getIdleLeases());
		}
		try {
			return _pool.borrowObject();
		} catch (Exception e) {
			throw handleError(e, "borrow lease");
		}
	}

	public void returnLease(JdbcCompiledQueryLease lease) {
		if (logger.isDebugEnabled()) {
			logger.debug("Returning lease. Leases (before): Active={}, Idle={}", getActiveLeases(), getIdleLeases());
		}
		try {
			_pool.returnObject(lease);
		} catch (Exception e) {
			throw handleError(e, "return lease");
		}
	}

	private RuntimeException handleError(Exception e, String message) {
		if (logger.isWarnEnabled()) {
			logger.warn("Unexpected error occurred in compiled JDBC query: " + message, e);
		}
		
		if (e instanceof SQLException) {
			return JdbcUtils.wrapException((SQLException) e, message);
		} else if (e instanceof RuntimeException) {
			return (RuntimeException) e;
		} else {
			return new MetaModelException(message, e);
		}
	}

	protected int getActiveLeases() {
		return _pool.getNumActive();
	}

	protected int getIdleLeases() {
		return _pool.getNumIdle();
	}

	protected Query getQuery() {
		return _query;
	}

	@Override
	public String toSql() {
		return _sql;
	}

	@Override
	public void close() {
		logger.debug("Closing compiled JDBC query: {}", _sql);
		try {
			_pool.close();
		} catch (Exception e) {
			throw handleError(e, "close pool of leases");
		} finally {
			_dataContext.close(_connection, null, null);
			_closed = true;
		}
	}

	protected List<SelectItem> getSelectItems() {
		return _query.getSelectClause().getItems();
	}

	@Override
	protected void finalize() throws Throwable {
		super.finalize();
		if (!_closed) {
			logger.warn("finalize() invoked, but DataSet is not closed. Invoking close() on {}", this);
			close();
		}
	}
}