org.guzz.id.SequenceHiLoGenerator.java Source code

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Here is the source code for org.guzz.id.SequenceHiLoGenerator.java

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/*
 * Copyright 2008-2009 the original author or authors.
 *
 * 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 org.guzz.id;

import java.io.Serializable;
import java.util.Properties;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.guzz.dialect.Dialect;
import org.guzz.orm.mapping.POJOBasedObjectMapping;
import org.guzz.transaction.WriteTranSession;
import org.guzz.util.StringUtil;

/**
 * <b>seqhilo</b><br>
 * <br>
 * An <tt>IdentifierGenerator</tt> that combines a hi/lo algorithm with an underlying
 * oracle-style sequence that generates hi values. The user may specify a
 * maximum lo value to determine how often new hi values are fetched.<br>
 * <br>
 * If sequences are not available, <tt>TableHiLoGenerator</tt> might be an
 * alternative.<br>
 * <br>
 * Mapping parameters supported: sequence, max_lo, db_group.
 *
 * @see TableHiLoGenerator
 */
public class SequenceHiLoGenerator extends SequenceIdGenerator {
    private static final Log log = LogFactory.getLog(SequenceHiLoGenerator.class);

    public static final String MAX_LO = "max_lo";

    private int maxLo;
    private int lo;
    private long hi;

    private Class returnType;

    public Serializable preInsert(WriteTranSession session, Object domainObject, Object tableCondition) {
        Serializable value = generate(session, tableCondition);

        setPrimaryKey(domainObject, value);

        return (Serializable) value;
    }

    public Serializable postInsert(WriteTranSession session, Object domainObject, Object tableCondition) {
        return super.postInsert(session, domainObject, tableCondition);
    }

    public void configure(Dialect dialect, POJOBasedObjectMapping mapping, Properties params) {
        super.configure(dialect, mapping, params);

        this.maxLo = StringUtil.toInt(params.getProperty(MAX_LO), 9);
        lo = maxLo + 1; // so we "clock over" on the first invocation
        this.returnType = pkDataType.getDataType();
    }

    public synchronized Number generate(WriteTranSession session, Object tableCondition) {
        if (maxLo < 1) {
            //keep the behavior consistent even for boundary usages
            Number n = (Number) super.nextSequenceValue(session, tableCondition);

            if (n.longValue() == 0L) {
                n = (Number) super.nextSequenceValue(session, tableCondition);
            }

            return IdentifierGeneratorFactory.createNumber(n.longValue(), this.returnType);
        }

        if (lo > maxLo) {
            Number n = (Number) super.nextSequenceValue(session, tableCondition);

            long hival = n.longValue();
            lo = (hival == 0) ? 1 : 0;
            hi = hival * (maxLo + 1);

            if (log.isDebugEnabled()) {
                log.debug("new hi value: " + hival);
            }
        }

        return IdentifierGeneratorFactory.createNumber(hi + lo++, this.returnType);
    }

}