基于单例模式的多键值序列号生成器兑现（带缓存）

基于单例模式的多键值序列号生成器实现（带缓存）

基本思路：
?* 数据库表通过Hibernate映射为实体类，主键通过序列号生成器（KeyGenerator）生成；
?* 序列号生成器以Singleton方式工作，并维护所有需要维护的实体的序列号（KeyBean）；
?* 列号生成器缓存一定的键值，避免每次取序列号都从数据库获取；
?* 数据库建立实体和当前键值对应表，每从列号生成器获取一个序列时，同步到该键值对应表，避免宕机后不一致

<!--<br /><br />Code highlighting produced by Actipro CodeHighlighter (freeware)<br />http://www.CodeHighlighter.com/<br /><br />-->??1package?com.pro.base.util;
??2
??3import?java.util.Map;
??4import?java.util.concurrent.ConcurrentHashMap;
??5import?org.springframework.beans.BeansException;
??6import?org.springframework.context.ApplicationContext;
??7import?org.springframework.context.ApplicationContextAware;
??8
??9import?com.pro.base.model.TableKey;
?10import?com.pro.base.service.BasicService;
?11
?12/**?*//***
?13?*?基于单例模式的多键值带缓存序列号生成器
?14?*?
?15?*?思路：
?16?*?数据库表通过Hibernate映射为实体类，主键通过序列号生成器（KeyGenerator）生成；
?17?*?序列号生成器以Singleton方式工作，并维护所有需要维护的实体的序列号（KeyBean）；
?18?*?列号生成器缓存一定的键值，避免每次取序列号都从数据库获取；
?19?*?数据库建立实体和当前键值对应表，每从列号生成器获取一个序列时，同步到该键值对应表，避免宕机后不一致
?20?*?
?21?*?@author?o_oand0_0
?22?*
?23?*/
?24public?class?KeyGenerator?implements?ApplicationContextAware?{
?25????
?26????//实现ApplicationContextAware,Spring对applicationContext自动装配；需要把KeyGenerator配置到Spring容器
?27????private??ApplicationContext?applicationContext;
?28
?29????//键值实体类
?30????private?Map<String,?KeyBean>?keyMap;
?31????
?32????//数据库服务
?33????private?BasicService?basicService;
?34????
?35????//设置要缓存的键值的数量，建议在团队开发测试时设为1，省得总出现主键冲突，到上线后再调大
?36????private?static?long?keyNum=20;
?37????
?38????private?static?final?KeyGenerator?instance=null;
?39????
?40????private?KeyGenerator()?{
?41????????basicService=(BasicService)applicationContext.getBean("basicService");
?42????}
?43????
?44????public??ApplicationContext?getApplicationContext()?{
?45????????return?applicationContext;
?46????}
?47
?48????@Override
?49????public?void?setApplicationContext(ApplicationContext?applicationContext)
?50????????????throws?BeansException?{
?51????????this.applicationContext=applicationContext;
?52????}
?53????
?54????//以单例方式获取序列号生成器
?55????public?static?synchronized??KeyGenerator?getInstance(){
?56????????if(instance==null){
?57????????????return?new?KeyGenerator();
?58????????}else{
?59????????????return?instance;
?60????????}
?61????}
?62????
?63????/**?*//**
?64?????*?根据类名获取序列号
?65?????*?@param?clazz
?66?????*?@return
?67?????*/
?68????public??String?generatorKey(Class?clazz){
?69????????return?getKey(clazz);
?70????}
?71
?72????/**?*//**
?73?????*?生成序列号，并同步至数据库
?74?????*?此方法可以根据自己需要定义生成序列号的规则
?75?????*?@param?clazz
?76?????*?@return
?77?????*/
?78????public?String?getKey(Class?clazz)?{
?79????????if?(keyMap?==?null)?{
?80????????????keyMap?=?new?ConcurrentHashMap<String,?KeyBean>();
?81????????}
?82????????KeyBean?kb?=?keyMap.get(clazz.getName());
?83????????if?(kb?==?null||kb.getMaxIndex()==kb.getNowIndex())?{
?84????????????updateKeyBean(clazz.getName());
?85????????}
?86????????kb?=?keyMap.get(clazz.getName());
?87????????long?now=kb.getNowIndex();
?88????????kb.setNowIndex(now+1);
?89????????return?now+"";
?90????}
?91
?92????/**?*//**
?93?????*?同步序列值到数据库，并修改序列号生成器对应实体的下一键值
?94?????*?@param?classPath
?95?????*/
?96????private?void?updateKeyBean(String?classPath)?{
?97????????TableKey?tk?=?(TableKey)?basicService.expandObjectByKey(TableKey.class.getName(),
?98????????????????classPath);
?99????????KeyBean?kb=new?KeyBean();
100????????kb.setKeyName(classPath);
101????????try?{
102????????????if?(tk?==?null)?{
103????????????????tk=new?TableKey();
104????????????????kb.setMaxIndex(keyNum);
105????????????????kb.setNowIndex(1);
106????????????????tk.setTableName(classPath);
107????????????????tk.setNowIndex(""+keyNum);
108????????????????basicService.insert(tk);
109????????????}?else?{
110????????????????kb.setMaxIndex(keyNum+Long.valueOf(tk.getNowIndex()));
111????????????????kb.setNowIndex(Long.valueOf(tk.getNowIndex()));
112????????????????tk.setNowIndex(Long.valueOf(tk.getNowIndex())?+?keyNum?+?"");
113????????????????basicService.update(tk);
114????????????}
115????????????keyMap.put(classPath,?kb);????????????
116????????}?catch?(Exception?e)?{
117????????????e.printStackTrace();
118????????}
119????}
120
121????public?Map<String,?KeyBean>?getKeyMap()?{
122????????return?keyMap;
123????}
124
125????public?void?setKeyMap(Map<String,?KeyBean>?keyMap)?{
126????????this.keyMap?=?keyMap;
127????}
128
129????public?BasicService?getBasicService()?{
130????????return?basicService;
131????}
132
133????
134????public?void?setBasicService(BasicService?basicService)?{
135????????this.basicService?=?basicService;
136????}
137????
138????/**?*//***
139?????*?键值实体类
140?????*?@author?o_oand0_0
141?????*
142?????*/
143????protected?class?KeyBean?{
144????????private?String?keyName;
145????????private?long?nowIndex;
146????????private?long?maxIndex;
147
148????????public?String?getKeyName()?{
149????????????return?keyName;
150????????}
151
152????????public?void?setKeyName(String?keyName)?{
153????????????this.keyName?=?keyName;
154????????}
155
156????????public?long?getNowIndex()?{
157????????????return?nowIndex;
158????????}
159
160????????public?void?setNowIndex(long?nowIndex)?{
161????????????this.nowIndex?=?nowIndex;
162????????}
163
164????????public?long?getMaxIndex()?{
165????????????return?maxIndex;
166????????}
167
168????????public?void?setMaxIndex(long?maxIndex)?{
169????????????this.maxIndex?=?maxIndex;
170????????}
171????}
172????
173}
1 楼 tan4836128 2011-10-25   有什么用？连实现场景都不能介绍，只能走马观花打打酱油，这样的文章也能上ITeye首页，不值一读！ 2 楼 sssheep 2011-10-25   集群方式下能保证不产生重复的？ 3 楼 o_oand0_0 2011-12-28   sssheep 写道集群方式下能保证不产生重复的？

我来替楼主回答：
集群方式下只要把取键的数量设为1就可以。相当于每次取键都和数据库同步。
另外，请楼主标明为转载。
地址：http://www.blogjava.net/o-oand0-0/archive/2011/10/21/361752.html
本人虽然写得不怎么的，但对于程序员来说，程序就像亲儿子。

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