package org.g4studio.core.id.sequence;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.g4studio.core.id.CreateSequnceException;
import org.g4studio.core.id.InitSequenceGeneratorException;
import org.g4studio.core.id.SequenceGenerator;
import org.g4studio.core.id.SequenceStorer;
import org.g4studio.core.id.storer.FileSequenceStorer;
/**
* DefaultSequenceGenerator
* 此代码源于开源项目E3,原作者：黄云辉
*
* @author XiongChun
* @since 2010-03-17
* @see SequenceGenerator
*/
public class DefaultSequenceGenerator implements SequenceGenerator {
/**
* 序号最小值
*/
protected long minValue = 0L;
/**
* 序号最大值
*/
protected long maxValue = Long.MAX_VALUE;
/**
* cache大小，用于确定预分配序号数;cache越大，ＩＤ生成效率越高，但是当系统 关闭时，可能造成的ＩＤ浪费也会更多.
*/
protected int cache = 100;
/**
* 是否循环生成，当cycle达到最大值时，是否循环，又从最小值开始生成
*/
protected boolean cycle = true;
/**
* 用于存储／读取 已分配出去的最大序号
*/
protected SequenceStorer sequenceStorer = new FileSequenceStorer();
protected long currCount = 0L;// 当前实际已分配序号最大值
protected long maxCount = cache + currCount;// 可以分配最大序号值（
protected String id = "anonymity";// 序号的标致符号
protected boolean initiated = false;
protected final Log logger = LogFactory
.getLog(DefaultSequenceGenerator.class);
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public DefaultSequenceGenerator() {
}
public DefaultSequenceGenerator(String pId) {
this.id = pId;
}
public void init() {
initiated = true;
long initValue = sequenceStorer.load(this.getId());
initValue = java.lang.Math.max(initValue, minValue);
if (initValue > maxValue) {
if (this.cycle) {
initValue = this.minValue;
} else {
final String msg = this.id + " 序号生成器的序号已经达到最大值:" + maxValue
+ " 了！系统无法在分配序号！";
logger.error(msg);
throw new InitSequenceGeneratorException(msg);
}
}
currCount = initValue;
maxCount = currCount + cache;
maxCount = java.lang.Math.min(maxCount, maxValue);
sequenceStorer.updateMaxValueByFieldName(maxCount, this.getId());
}
public long next() throws CreateSequnceException {
if (initiated == false) {
init();
}
if (currCount == maxCount) {// 重新申请id
long tmp = maxCount + cache;
if (tmp >= maxValue) {
if (this.cycle) {
tmp = this.minValue;
} else {
final String msg = this.id + " 序号生成器的序号已经达到最大值:" + maxValue
+ " 了！系统无法在分配序号！";
logger.error(msg);
throw new CreateSequnceException(msg);
}
}
sequenceStorer.updateMaxValueByFieldName(tmp, this.getId());
maxCount = tmp;
}
currCount++;
return currCount;
}
public long getMinValue() {
return minValue;
}
public void setMinValue(long minValue) {
this.minValue = minValue;
}
public long getMaxValue() {
return maxValue;
}
public void setMaxValue(long maxValue) {
this.maxValue = maxValue;
}
public int getCache() {
return cache;
}
public void setCache(int cache) {
this.cache = cache;
}
public boolean isCycle() {
return cycle;
}
public void setCycle(boolean cycle) {
this.cycle = cycle;
}
public void setSequenceStorer(SequenceStorer sequenceStorer) {
this.sequenceStorer = sequenceStorer;
}
}