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/*
* Copyright 2000-2014 Vaadin Ltd.
*
* Licensed 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 com.vaadin.data.util.sqlcontainer.query;
import java.io.Serializable;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import com.vaadin.data.util.sqlcontainer.connection.JDBCConnectionPool;
/**
* Common base class for database query classes that handle connections and
* transactions.
*
* @author Vaadin Ltd
* @since 6.8.9
*/
public abstract class AbstractTransactionalQuery implements Serializable {
private JDBCConnectionPool connectionPool;
private transient Connection activeConnection;
AbstractTransactionalQuery() {
}
AbstractTransactionalQuery(JDBCConnectionPool connectionPool) {
this.connectionPool = connectionPool;
}
/**
* Reserves a connection with auto-commit off if no transaction is in
* progress.
*
* @throws IllegalStateException
* if a transaction is already open
* @throws SQLException
* if a connection could not be obtained or configured
*/
public void beginTransaction() throws UnsupportedOperationException,
SQLException {
if (isInTransaction()) {
throw new IllegalStateException("A transaction is already active!");
}
activeConnection = connectionPool.reserveConnection();
activeConnection.setAutoCommit(false);
}
/**
* Commits (if not in auto-commit mode) and releases the active connection.
*
* @throws SQLException
* if not in a transaction managed by this query
*/
public void commit() throws UnsupportedOperationException, SQLException {
if (!isInTransaction()) {
throw new SQLException("No active transaction");
}
if (!activeConnection.getAutoCommit()) {
activeConnection.commit();
}
connectionPool.releaseConnection(activeConnection);
activeConnection = null;
}
/**
* Rolls back and releases the active connection.
*
* @throws SQLException
* if not in a transaction managed by this query
*/
public void rollback() throws UnsupportedOperationException, SQLException {
if (!isInTransaction()) {
throw new SQLException("No active transaction");
}
activeConnection.rollback();
connectionPool.releaseConnection(activeConnection);
activeConnection = null;
}
/**
* Check that a transaction is active.
*
* @throws SQLException
* if no active transaction
*/
protected void ensureTransaction() throws SQLException {
if (!isInTransaction()) {
throw new SQLException("No active transaction!");
}
}
/**
* Closes a statement and a resultset, then releases the connection if it is
* not part of an active transaction. A failure in closing one of the
* parameters does not prevent closing the rest.
*
* If the statement is a {@link PreparedStatement}, its parameters are
* cleared prior to closing the statement.
*
* Although JDBC specification does state that closing a statement closes
* its result set and closing a connection closes statements and result
* sets, this method does try to close the result set and statement
* explicitly whenever not null. This can guard against bugs in certain JDBC
* drivers and reduce leaks in case e.g. closing the result set succeeds but
* closing the statement or connection fails.
*
* @param conn
* the connection to release
* @param statement
* the statement to close, may be null to skip closing
* @param rs
* the result set to close, may be null to skip closing
* @throws SQLException
* if closing the result set or the statement fails
*/
protected void releaseConnection(Connection conn, Statement statement,
ResultSet rs) throws SQLException {
try {
try {
if (null != rs) {
rs.close();
}
} finally {
if (null != statement) {
if (statement instanceof PreparedStatement) {
try {
((PreparedStatement) statement).clearParameters();
} catch (Exception e) {
// will be closed below anyway
}
}
statement.close();
}
}
} finally {
releaseConnection(conn);
}
}
/**
* Returns the currently active connection, reserves and returns a new
* connection if no active connection.
*
* @return previously active or newly reserved connection
* @throws SQLException
*/
protected Connection getConnection() throws SQLException {
if (activeConnection != null) {
return activeConnection;
}
return connectionPool.reserveConnection();
}
protected boolean isInTransaction() {
return activeConnection != null;
}
/**
* Releases the connection if it is not part of an active transaction.
*
* @param conn
* the connection to release
*/
private void releaseConnection(Connection conn) {
if (conn != activeConnection && conn != null) {
connectionPool.releaseConnection(conn);
}
}
}
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