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/* ====================================================================
 * 
 * The ObjectStyle Group Software License, version 1.1
 * ObjectStyle Group - http://objectstyle.org/
 * 
 * Copyright (c) 2002-2005, Andrei (Andrus) Adamchik and individual authors
 * of the software. All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 
 * 3. The end-user documentation included with the redistribution, if any,
 *    must include the following acknowlegement:
 *    "This product includes software developed by independent contributors
 *    and hosted on ObjectStyle Group web site (http://objectstyle.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
 * 
 * 4. The names "ObjectStyle Group" and "Cayenne" must not be used to endorse
 *    or promote products derived from this software without prior written
 *    permission. For written permission, email
 *    "andrus at objectstyle dot org".
 * 
 * 5. Products derived from this software may not be called "ObjectStyle"
 *    or "Cayenne", nor may "ObjectStyle" or "Cayenne" appear in their
 *    names without prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE OBJECTSTYLE GROUP OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 * 
 * This software consists of voluntary contributions made by many
 * individuals and hosted on ObjectStyle Group web site.  For more
 * information on the ObjectStyle Group, please see
 * .
 */
package org.objectstyle.cayenne.dba.mysql;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Collections;

import org.objectstyle.cayenne.access.DataNode;
import org.objectstyle.cayenne.access.QueryLogger;
import org.objectstyle.cayenne.dba.JdbcPkGenerator;
import org.objectstyle.cayenne.map.DbEntity;

/**
 * @author Andrei Adamchik
 */
public class MySQLPkGenerator extends JdbcPkGenerator {

    protected String dropAutoPkString() {
        return "DROP TABLE IF EXISTS AUTO_PK_SUPPORT";
    }

    /**
     * Overrides superclass's implementation to perform locking of the primary key lookup
     * table.
     */
    protected int pkFromDatabase(DataNode node, DbEntity ent) throws Exception {

        // must work directly with JDBC connection, since we
        // must unlock the AUTO_PK_SUPPORT table in case of
        // failures.... ah..JDBC is fun...

        // chained SQL exception
        SQLException exception = null;
        int pk = -1;

        Connection con = node.getDataSource().getConnection();
        try {
            
            if(con.getAutoCommit()) {
                con.setAutoCommit(false);
            }
            
            Statement st = con.createStatement();

            try {
                pk = getPrimaryKey(st, ent.getName());
                con.commit();
            }
            catch (SQLException pkEx) {
                
                try {
                    con.rollback();
                }
                catch (SQLException e) {

                }
                
                exception = processSQLException(pkEx, exception);
            }
            finally {
                // UNLOCK!
                // THIS MUST BE EXECUTED NO MATTER WHAT, OR WE WILL LOCK THE PRIMARY KEY
                // TABLE!!
                try {
                    String unlockString = "UNLOCK TABLES";
                    QueryLogger.logQuery(unlockString, Collections.EMPTY_LIST);
                    st.execute(unlockString);
                }
                catch (SQLException unlockEx) {
                    exception = processSQLException(unlockEx, exception);
                }
                finally {
                    // close statement
                    try {
                        st.close();
                    }
                    catch (SQLException stClosingEx) {
                        // ignoring...
                    }
                }
            }
        }
        catch (SQLException otherEx) {
            exception = processSQLException(otherEx, exception);
        }
        finally {
            try {
                con.close();
            }
            catch (SQLException closingEx) {
                // ignoring
            }
        }

        // check errors
        if (exception != null) {
            throw exception;
        }

        return pk;
    }

    /**
     * Appends a new SQLException to the chain. If parent is null, uses the exception as
     * the chain root.
     */
    protected SQLException processSQLException(SQLException exception, SQLException parent) {
        if (parent == null) {
            return exception;
        }

        parent.setNextException(exception);
        return parent;
    }

    protected String pkTableCreateString() {
        StringBuffer buf = new StringBuffer();
        buf.append("CREATE TABLE AUTO_PK_SUPPORT (").append(
                "  TABLE_NAME CHAR(100) NOT NULL,").append(
                "  NEXT_ID INTEGER NOT NULL, UNIQUE (TABLE_NAME)").append(")");

        return buf.toString();
    }

    protected int getPrimaryKey(Statement statement, String entityName)
            throws SQLException {
        // lock
        String lockString = "LOCK TABLES AUTO_PK_SUPPORT WRITE";
        QueryLogger.logQuery(lockString, Collections.EMPTY_LIST);
        statement.execute(lockString);

        // select
        int pk = -1;

        String selectString = super.pkSelectString(entityName);
        QueryLogger.logQuery(selectString, Collections.EMPTY_LIST);
        ResultSet rs = statement.executeQuery(selectString);
        try {
            if (!rs.next()) {
                throw new SQLException("No rows for '" + entityName + "'");
            }

            pk = rs.getInt(1);

            if (rs.next()) {
                throw new SQLException("More than one row for '" + entityName + "'");
            }
        }
        finally {
            try {
                rs.close();
            }
            catch (Exception ex) {
                // ignoring...
            }
        }

        // update
        String updateString = super.pkUpdateString(entityName) + " AND NEXT_ID = " + pk;
        QueryLogger.logQuery(updateString, Collections.EMPTY_LIST);
        int updated = statement.executeUpdate(updateString);
        // optimistic lock failure...
        if (updated != 1) {
            throw new SQLException("Error updating PK count '"
                    + entityName
                    + "': "
                    + updated);
        }

        return pk;
    }
}