KeySequenceDirect.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.aries.samples.ariestrader.persist.jdbc;

import java.util.Collection;
import java.util.Iterator;
import java.util.HashMap;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

import org.apache.aries.samples.ariestrader.util.*;

public class KeySequenceDirect {

    private static HashMap keyMap = new HashMap();

    public static synchronized Integer getNextID(Connection conn, String keyName, boolean inSession, boolean inGlobalTxn)
        throws Exception {
        Integer nextID = null;
        // First verify we have allocated a block of keys
        // for this key name
        // Then verify the allocated block has not been depleted
        // allocate a new block if necessary
        if (keyMap.containsKey(keyName) == false)
            allocNewBlock(conn, keyName, inSession, inGlobalTxn);
        Collection block = (Collection) keyMap.get(keyName);

        Iterator ids = block.iterator();
        if (ids.hasNext() == false)
            ids = allocNewBlock(conn, keyName, inSession, inGlobalTxn).iterator();
        // get and return a new unique key
        nextID = (Integer) ids.next();

        if (Log.doTrace())
            Log.trace("KeySequenceDirect:getNextID inSession(" + inSession + ") - return new PK ID for Entity type: "
                + keyName + " ID=" + nextID);
        return nextID;
    }

    private static Collection allocNewBlock(Connection conn, String keyName, boolean inSession, boolean inGlobalTxn)
        throws Exception {
        try {
            if (inGlobalTxn == false && !inSession)
                conn.commit(); // commit any pending txns
            PreparedStatement stmt = conn.prepareStatement(getKeyForUpdateSQL);
            stmt.setString(1, keyName);
            ResultSet rs = stmt.executeQuery();
            if (!rs.next()) {
                // No keys found for this name - create a new one
                PreparedStatement stmt2 = conn.prepareStatement(createKeySQL);
                int keyVal = 0;
                stmt2.setString(1, keyName);
                stmt2.setInt(2, keyVal);
                stmt2.executeUpdate();
                stmt2.close();
                stmt.close();
                stmt = conn.prepareStatement(getKeyForUpdateSQL);
                stmt.setString(1, keyName);
                rs = stmt.executeQuery();
                rs.next();
            }

            int keyVal = rs.getInt("keyval");

            stmt.close();

            stmt = conn.prepareStatement(updateKeyValueSQL);
            stmt.setInt(1, keyVal + TradeConfig.KEYBLOCKSIZE);
            stmt.setString(2, keyName);
            stmt.executeUpdate();
            stmt.close();

            Collection block = new KeyBlock(keyVal, keyVal + TradeConfig.KEYBLOCKSIZE - 1);
            keyMap.put(keyName, block);
            if (inGlobalTxn == false && !inSession)
                conn.commit();
            return block;
        } catch (Exception e) {
            String error =
                "KeySequenceDirect:allocNewBlock - failure to allocate new block of keys for Entity type: " + keyName;
            Log.error(e, error);
            throw new Exception(error + e.toString());
        }
    }

    private static final String getKeyForUpdateSQL = "select * from keygenejb kg where kg.keyname = ?  for update";

    private static final String createKeySQL =
        "insert into keygenejb " + "( keyname, keyval ) " + "VALUES (  ?  ,  ? )";

    private static final String updateKeyValueSQL = "update keygenejb set keyval = ? " + "where keyname = ?";

}