cn.edu.ahpu.common.dao.key.SingleSequence.java Source code

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Here is the source code for cn.edu.ahpu.common.dao.key.SingleSequence.java

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/*
 * Copyright 2010-2011 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 cn.edu.ahpu.common.dao.key;

import java.util.concurrent.locks.ReentrantLock;

import org.springframework.transaction.TransactionStatus;
import org.springframework.transaction.interceptor.TransactionAttribute;
import org.springframework.transaction.support.TransactionCallback;
import org.springframework.transaction.support.TransactionTemplate;

/**
 * 
 * @author libinsong1204@gmail.com
 * @version 1.0
 */
public class SingleSequence {
    private final ReentrantLock lock = new ReentrantLock(false);

    protected long currVal = 0L;

    protected long maxVal = 0L;

    private final int cacheNum;

    private final UniqueTableApp app;

    private final TransactionTemplate transactionTemplate;

    public SingleSequence(int cacheNum, UniqueTableApp app, TransactionTemplate transactionTemplate) {
        this.cacheNum = cacheNum;
        this.app = app;
        this.transactionTemplate = transactionTemplate;
    }

    public long getNextVal(String name) {
        try {
            lock.lock();
            if (this.currVal < this.maxVal) {
                return (this.currVal++);
            }
            CacheValue cache = getNewValFromDB(name);
            this.currVal = cache.getMinVal();
            this.maxVal = cache.getMaxVal();
            return (this.currVal++);
        } finally {
            lock.unlock();
        }
    }

    private CacheValue getNewValFromDB(final String name) {
        transactionTemplate.setPropagationBehavior(TransactionAttribute.PROPAGATION_REQUIRES_NEW);
        return transactionTemplate.execute(new TransactionCallback<CacheValue>() {

            @Override
            public CacheValue doInTransaction(TransactionStatus status) {
                return app.getCacheValue(cacheNum, name);
            }
        });
    }
}