sequence.java

一个很好的开源项目管理系统源代码

package net.java.workeffort.service.support;

import net.java.workeffort.infrastructure.sequence.ISequence;
import net.java.workeffort.service.ISequenceService;

/**
 * The sequence generator.
 * <p>
 * Thread and cluster save sequence generater which will work for all databases.
 * <p>
 * Will load a block of sequences and hand them out. When the block runs out of
 * sequences it will hit the database to get the next block of sequences. The
 * block size for each sequence is configured using Spring.
 * <p>
 * Note that there will be gaps in the sequence. This will happen any time you
 * bounce the application server. Also in a clustered environment the inserted
 * records will have sequences out of order (Unless you have the block size set
 * to 0) because each node in the cluster gets its own block of sequences.
 * @author Antony Joseph
 */
public class Sequence implements ISequence {

    private long currentKeyValue = -1; // not populated indicator.
    private long maxBlockKeyValue;

    private String name;
    private int blockSize;
    private ISequenceService sequenceService;

    public synchronized Long getNextId() {

        if (currentKeyValue < maxBlockKeyValue && currentKeyValue != -1)
            return new Long(++currentKeyValue);
        else {
            currentKeyValue = (sequenceService.getNextBlockSequenceId(name,
                    new Integer(blockSize))).longValue();
            maxBlockKeyValue = currentKeyValue + blockSize;
            return new Long(currentKeyValue);
        }
    }

    /**
     * @return Returns the blockSize.
     */
    public int getBlockSize() {
        return blockSize;
    }

    /**
     * @param blockSize The blockSize to set.
     */
    public void setBlockSize(int blockSize) {
        this.blockSize = blockSize;
    }

    /**
     * @return Returns the sequenceService.
     */
    public ISequenceService getSequenceService() {
        return sequenceService;
    }

    /**
     * @param sequenceService The sequenceService to set. IOC
     */
    public void setSequenceService(ISequenceService sequenceService) {
        this.sequenceService = sequenceService;
    }

    /**
     * @return Returns the name.
     */
    public String getName() {
        return name;
    }

    /**
     * @param name The name to set. IOC
     */
    public void setName(String name) {
        this.name = name;
    }

}