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redis作为hibernate的二级缓存

發(fā)布時(shí)間：2024/9/30 编程问答 28 豆豆

生活随笔收集整理的這篇文章主要介紹了 redis作为hibernate的二级缓存小編覺得挺不錯的,現(xiàn)在分享給大家,幫大家做個參考.

hibernate的二級緩存有好多，像ehcache。不過項(xiàng)目的緩存使用的是redis，而redis官方?jīng)]有實(shí)現(xiàn)hibernate的二級緩存接口，只得自己實(shí)現(xiàn)。看看公司的高手如何做的吧。

先看配置：

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   <!-- entityManagerFactory -->  ????<bean  id="entityManagerFactory"  class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"  ????????depends-on="cacheManagerFactory">  ????????...  ????????<property  name="jpaProperties">  ????????????<props>  ????????????????...  ????????????????<prop  key="hibernate.cache.use_second_level_cache">true</prop>  ????????????????<!-- <prop key="hibernate.cache.use_query_cache">true</prop> -->  ????????????????<prop  key="hibernate.cache.region.factory_class">xxx.xxx.framework.cache.hibernate.CacheRegionFactory</prop>  ????????????????...  ????????????</props>  ????????</property>  ????</bean>??   ?????  ????<!-- cache -->  ????<bean  id="cacheManager"  class="xxx.xxx.framework.cache.redis.RedisCacheManager">  ????????<property  name="connectionFactory"  ref="redisConnectionFactory"/>  ????????<property  name="namespace"  value="payment"/>  ????</bean>  ?????  ????<bean  id="cacheManagerFactory"  class="xxx.xxx.framework.cache.hibernate.CacheManagerFactory">  ????????<property  name="cacheManager"  ref="cacheManager"/>  ????</bean>  

cacheManager是redis緩存的配置，二級緩存實(shí)現(xiàn)類CacheRegionFactory里面會用到它，但是hibernate緩存配置的只是配置實(shí)現(xiàn)類，沒法注入CacheRegionFactory對象，所以這邊多了個cacheManagerFactory，注意配置中的depends-on。它的代碼：

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   public  final  class  CacheManagerFactory implements  DisposableBean {  ????private  static  CacheManager CACH_EMANAGER;   ????public  void  setCacheManager(CacheManager cacheManager) {  ????????CACH_EMANAGER = cacheManager;  ????}   ????public  static  CacheManager getCacheManager() {  ????????return  CACH_EMANAGER;  ????}   ????@Override  ????public  void  destroy() throws  Exception {  ????????CACH_EMANAGER = null;  ????}  }  

它就是負(fù)責(zé)生成cacheManager。注意getCacheManager是靜態(tài)方法。然后我們看redis二級緩存的實(shí)現(xiàn)類：

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   public  class  CacheRegionFactory implements  RegionFactory {  ????private  static  final  long  serialVersionUID = -1557439471733872383L;  ????private  CacheManager cacheManager;  ????private  static  final  AtomicLong CURRENT = new  AtomicLong();  ????protected  Settings settings;   ????@Override  ????public  void  start(Settings settings, Properties properties) throws  CacheException {  ????????cacheManager = CacheManagerFactory.getCacheManager();  ????????this.settings = settings;  ????????Assert.notNull(cacheManager, "cacheManager is required,CacheManagerFactory must be init first");  ????}   ????@Override  ????public  void  stop() {  ????????cacheManager = null;  ????}   ????@Override  ????public  boolean  isMinimalPutsEnabledByDefault() {  ????????return  true;  ????}   ????@Override  ????public  AccessType getDefaultAccessType() {  ????????return  AccessType.NONSTRICT_READ_WRITE;  ????}   ????@Override  ????public  long  nextTimestamp() {  ????????return  CURRENT.incrementAndGet();  ????}   ????@Override  ????public  EntityRegion buildEntityRegion(String regionName, Properties properties, CacheDataDescription metadata) throws  CacheException {  ????????return  new  EntityRegionImpl(regionName, cacheManager.getCache(shortRegionName(regionName)), settings, properties, metadata);  ????}   ????@Override  ????public  NaturalIdRegion buildNaturalIdRegion(String regionName, Properties properties, CacheDataDescription metadata) throws  CacheException {  ????????return  new  NaturalIdRegionImpl(regionName, cacheManager.getCache(shortRegionName(regionName)), settings, properties, metadata);  ????}   ????@Override  ????public  CollectionRegion buildCollectionRegion(String regionName, Properties properties, CacheDataDescription metadata) throws  CacheException {  ????????return  new  CollectionRegionImpl(regionName, cacheManager.getCache(shortRegionName(regionName)), settings, properties, metadata);  ????}   ????@Override  ????public  QueryResultsRegion buildQueryResultsRegion(String regionName, Properties properties) throws  CacheException {  ????????return  new  QueryResultsRegionImpl(regionName, cacheManager.getCache(shortRegionName(regionName)), settings, properties);  ????}   ????@Override  ????public  TimestampsRegion buildTimestampsRegion(String regionName, Properties properties)  throws  CacheException {  ????????return  new  TimestampsRegionImpl(regionName, cacheManager.getCache(shortRegionName(regionName)), settings, properties);  ????}   ????private  static  String shortRegionName(String regionName) {  ????????...  ????}  }  

RegionFactory是hibernate的接口。在start里面通過調(diào)用CacheManagerFactory來獲取redis的CacheManager。這里主要還是buildXX的幾個方法，在這些方法里面通過? CacheManager和region獲取cache，然后再生成hibernate需要的緩存對象。

以buildEntityRegion為例，返回的對象EntityRegion是hibernate的接口，EntityRegionImpl怎是我們的實(shí)現(xiàn)。先看看它的實(shí)現(xiàn)：

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   public  class  EntityRegionImpl extends  AbstractTransactionalDataRegion implements  EntityRegion {   ????public  EntityRegionImpl(String regionName, Cache cache, Settings settings, Properties properties, CacheDataDescription metadata) {  ????????super(regionName,cache, settings, properties, metadata);  ????}   ????@Override  ????public  EntityRegionAccessStrategy buildAccessStrategy(AccessType accessType) throws  CacheException {  ????????return  new  EntityRegionAccessStrategyImpl(this, settings);  ????}  }  

這邊可以分兩部分看了一個是它的父類AbstractTransactionalDataRegion，另外一個是由EntityRegion繼承而來的buildAccessStrategy（Hibernate?EntityRegion的接口實(shí)現(xiàn)）。

先看它的父類，父類實(shí)現(xiàn)了hibernate的TansactionalDateRegion：

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   public  class  AbstractTransactionalDataRegion extends  AbstractRegion implements  TransactionalDataRegion {  ????private  final  CacheDataDescription metadata;   ????public  AbstractTransactionalDataRegion(String regionName, Cache cache, Settings settings, Properties properties, CacheDataDescription metadata) {  ????????super(regionName, cache, settings, properties);  ????????this.metadata = metadata;  ????}   ????@Override  ????public  boolean  isTransactionAware() {  ????????return  false;  ????}   ????@Override  ????public  CacheDataDescription getCacheDataDescription() {  ????????return  metadata;  ????}  }  

isTransactionAware是表示是否支持jta事務(wù)。然后再看它的父類AbstractRegion： ?

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   public  class  AbstractRegion implements  Region {  ????private  static  final  AtomicLong CURRENT = new  AtomicLong();  ????private  String regionName;  ????protected  final  Cache cache;  ????protected  final  Properties properties;  ????protected  final  Settings settings;  ????protected  final  KeyGenerator keyGenerator = DefaultKeyGenerator.INSTANCE;   ????public  AbstractRegion(String regionName, Cache cache, Settings settings, Properties properties) {  ????????this.regionName = regionName;  ????????this.cache = cache;  ????????this.settings = settings;  ????????this.properties = properties;  ????}   ????@Override  ????public  String getName() {  ????????return  regionName;  ????}   ????@Override  ????public  void  destroy() throws  CacheException {  ????}   ????@Override  ????public  boolean  contains(Object key) {  ????????return  cache.exists(key);  ????}   ????@Override  ????public  long  getSizeInMemory() {  ????????return  -1;  ????}   ????@Override  ????public  long  getElementCountInMemory() {  ????????return  cache.getStatistics().getSize();  ????}   ????@Override  ????public  long  getElementCountOnDisk() {  ????????return  -1;  ????}   ????@Override  ????public  Map toMap() {  ????????return  Collections.EMPTY_MAP;  ????}   ????@Override  ????public  long  nextTimestamp() {  ????????return  CURRENT.incrementAndGet();  ????}   ????@Override  ????public  int  getTimeout() {  ????????return  300;  ????}   ????public  Object get(Object key) throws  CacheException {  ????????try  {  ????????????return  postGet(cache.get(toKey(key)));  ????????} catch  (Throwable e) {  ????????????throw  new  CacheException(e);  ????????}  ????}   ????public  void  put(Object key, Object value) throws  CacheException {  ????????try  {  ????????????cache.put(toKey(key), value);  ????????} catch  (Exception e) {  ????????????throw  new  CacheException(e);  ????????}  ????}   ????public  void  evict(Object key) throws  CacheException {  ????????try  {  ????????????cache.evict(toKey(key));  ????????} catch  (Exception e) {  ????????????throw  new  CacheException(e);  ????????}  ????}   ????public  void  evictAll() throws  CacheException {  ????????try  {  ????????????cache.clear();  ????????} catch  (Exception e) {  ????????????throw  new  CacheException(e);  ????????}  ????}   ????private  Object toKey(Object key) {  ????????if  (key instanceof  CacheKey) {  ????????????key = ((CacheKey) key).getKey();  ????????}  ????????return  keyGenerator.generate(key);  ????}  ......  

這里實(shí)現(xiàn)了hibernate region的一些接口，另外一些對于緩存的一些操作方法如:put\get\evict等也做了實(shí)現(xiàn)。

現(xiàn)在我們回過頭看看EntityRegionImpl里面的EntityRegionAccessStrategyImpl實(shí)現(xiàn)：

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   public  class  EntityRegionAccessStrategyImpl extends  AbstractAccessStrategy<EntityRegionImpl> implements  EntityRegionAccessStrategy {    ??? public  EntityRegionAccessStrategyImpl(EntityRegionImpl region, Settings settings) {  ??? ? ? super(region, settings);  ??? }    ??? @Override  ??? public  EntityRegion getRegion() {  ??? ? ? return  region;  ??? }  }  

它也實(shí)現(xiàn)了hibernate的接口：EntityRegionAccessStrategy，字面意思就是緩存的訪問策略。

先看看hibernate的這個接口的定義:

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   public  interface  EntityRegionAccessStrategy extends  RegionAccessStrategy{   ????/**  ?????* Get the wrapped entity cache region  ?????*  ?????* @return The underlying region  ?????*/  ????public  EntityRegion getRegion();   ????/**  ?????* Called after an item has been inserted (before the transaction completes),  ?????* instead of calling evict().  ?????* This method is used by "synchronous" concurrency strategies.  ?????*  ?????* @param key The item key  ?????* @param value The item  ?????* @param version The item's version value  ?????* @return Were the contents of the cache actual changed by this operation?  ?????* @throws CacheException Propogated from underlying {@link org.hibernate.cache.spi.Region}  ?????*/  ????public  boolean  insert(Object key, Object value, Object version) throws  CacheException;   ????/**  ?????* Called after an item has been inserted (after the transaction completes),  ?????* instead of calling release().  ?????* This method is used by "asynchronous" concurrency strategies.  ?????*  ?????* @param key The item key  ?????* @param value The item  ?????* @param version The item's version value  ?????* @return Were the contents of the cache actual changed by this operation?  ?????* @throws CacheException Propogated from underlying {@link org.hibernate.cache.spi.Region}  ?????*/  ????public  boolean  afterInsert(Object key, Object value, Object version) throws  CacheException;   ????/**  ?????* Called after an item has been updated (before the transaction completes),  ?????* instead of calling evict(). This method is used by "synchronous" concurrency  ?????* strategies.  ?????*  ?????* @param key The item key  ?????* @param value The item  ?????* @param currentVersion The item's current version value  ?????* @param previousVersion The item's previous version value  ?????* @return Were the contents of the cache actual changed by this operation?  ?????* @throws CacheException Propogated from underlying {@link org.hibernate.cache.spi.Region}  ?????*/  ????public  boolean  update(Object key, Object value, Object currentVersion, Object previousVersion)  throws  CacheException;   ????/**  ?????* Called after an item has been updated (after the transaction completes),  ?????* instead of calling release().? This method is used by "asynchronous"  ?????* concurrency strategies.  ?????*  ?????* @param key The item key  ?????* @param value The item  ?????* @param currentVersion The item's current version value  ?????* @param previousVersion The item's previous version value  ?????* @param lock The lock previously obtained from {@link #lockItem}  ?????* @return Were the contents of the cache actual changed by this operation?  ?????* @throws CacheException Propogated from underlying {@link org.hibernate.cache.spi.Region}  ?????*/  ????public  boolean  afterUpdate(Object key, Object value, Object currentVersion, Object previousVersion, SoftLock lock) throws  CacheException;  }  

它的父接口里面還有一些其他的接口如get，remove等可以直接看看源碼注釋上面都寫了。

我們的實(shí)現(xiàn)類同時(shí)有個父類AbstractAccessStrategy<EntityRegionImpl>，很多EntityRegionAccessStrategy因?yàn)槎际枪玫乃栽贏bstractAccessStrategy中實(shí)現(xiàn)了。看代碼：

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   public  abstract  class  AbstractAccessStrategy<T extends  AbstractTransactionalDataRegion> {  ????protected  final  T region;  ????protected  final  Settings settings;   ????public  AbstractAccessStrategy(T region, Settings settings) {  ????????this.region = region;  ????????this.settings = settings;  ????}   ????public  boolean  insert(Object key, Object value) throws  CacheException {  ????????return  insert(key, value, null);  ????}   ????public  boolean  insert(Object key, Object value, Object version) throws  CacheException {  ????????return  false;  ????}   ????public  boolean  afterInsert(Object key, Object value) throws  CacheException {  ????????return  afterInsert(key, value, null);  ????}   ????public  boolean  afterInsert(Object key, Object value, Object version) throws  CacheException {  ????????return  false;  ????}   ????public  boolean  update(Object key, Object value) throws  CacheException {  ????????return  update(key, value, null, null);  ????}   ????public  boolean  update(Object key, Object value, Object currentVersion, Object previousVersion)  throws  CacheException {  ????????remove(key);  ????????return  false;  ????}   ????public  boolean  afterUpdate(Object key, Object value, SoftLock lock) throws  CacheException {  ????????return  afterUpdate(key, value, null, null, lock);  ????}   ????public  boolean  afterUpdate(Object key, Object value, Object currentVersion, Object previousVersion, SoftLock lock) throws  CacheException {  ????????unlockItem(key, lock);  ????????return  false;  ????}   ????public  Object get(Object key, long  txTimestamp) throws  CacheException {  ????????return  region.get(key);  ????}   ????public  boolean  putFromLoad(Object key, Object value, long  txTimestamp, Object version) throws  CacheException {  ????????return  putFromLoad(key, value, txTimestamp, version, settings.isMinimalPutsEnabled());  ????}   ????public  boolean  putFromLoad(Object key, Object value, long  txTimestamp, Object version, boolean  minimalPutOverride) throws  CacheException {  ????????if  (minimalPutOverride && region.contains(key)) {  ????????????return  false;  ????????} else  {  ????????????region.put(key, value);  ????????????return  true;  ????????}  ????}   ????public  SoftLock lockItem(Object key, Object version) throws  CacheException {  ????????return  null;  ????}   ????public  SoftLock lockRegion() throws  CacheException {  ????????return  null;  ????}   ????public  void  unlockItem(Object key, SoftLock lock) throws  CacheException {  ????????region.evict(key);  ????}   ????public  void  unlockRegion(SoftLock lock) throws  CacheException {  ????????region.evictAll();  ????}   ????public  void  remove(Object key) throws  CacheException {  ????????region.evict(key);  ????}   ????public  void  removeAll() throws  CacheException {  ????????region.evictAll();  ????}   ????public  void  evict(Object key) throws  CacheException {  ????????region.evict(key);  ????}   ????public  void  evictAll() throws  CacheException {  ????????region.evictAll();  ????}  }  

上面的方法有些怪異如insert方法，里面就直接返回false了，問了高手，他說參考ehcache的實(shí)現(xiàn)。看了下ehcache的源碼它上面寫了：A no-op since this is an asynchronous cache access strategy。這個和hibernate接口定義的insert注釋有點(diǎn)出入:

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   * Called after an item has been inserted (before the transaction completes),  ?????* instead of calling evict().  ?????* This method is used by "synchronous"  concurrency strategies.  

總之這塊不是很理解。

轉(zhuǎn)http://my.oschina.net/yybear/blog/102216

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