路漫漫其修遠(yuǎn)兮，吾將上下而求索！

<!--?Hibernate?SessionFactory?-->
????<bean?id="sessionFactory"?class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">
????????<property?name="dataSource"?ref="dataSource"/>
????????<property?name="mappingResources">
????????<list>
????????????<value>com/ouou/model/Videos.hbm.xml</value>???
?????????</list>
?????????</property>
????????<property?name="hibernateProperties">
????????????<props>
????????????????<prop?key="hibernate.dialect">org.hibernate.dialect.MySQLDialect</prop>
????????????????<prop?key="hibernate.current_session_context_class">thread</prop>
????????????????<prop?key="hibernate.cglib.use_reflection_optimizer">false</prop>
????????????????<prop?key="hibernate.query.substitutions">true?'Y',?false?'N'</prop>
????????????????<!--add?ehcache-->
????????????????<prop?key="hibernate.cache.provider_class">org.hibernate.cache.EhCacheProvider</prop>
????????????????<prop?key="hibernate.cache.use_query_cache">false</prop><!--?是否使用查詢緩存?-->
????????????????<!--
????????????????<prop?key="hibernate.cache.provider_configuration_file_resource_path">/ehcache.xml</prop>
????????????????<prop?key="hibernate.show_sql">true</prop>
????????????????-->
????????????????<!--<prop?key="hibernate.transaction.auto_close_session">true</prop>-->
????????????????<prop?key="connection.provider_class">org.hibernate.connection.C3P0ConnectionProvider</prop>
????????????????<!--?Create/update?the?database?tables?automatically?when?the?JVM?starts?up
?????????????????<prop?key="hibernate.hbm2ddl.auto">update</prop>?-->
????????????????<!--?Turn?batching?off?for?better?error?messages?under?PostgreSQL?-->
????????????????<prop?key="hibernate.jdbc.batch_size">25</prop>
????????????????<!--
????????????????<prop?key="hibernate.connection.pool_size">10</prop>
????????????????-->
????????????</props>
????????</property>
????</bean>

??? 如果不設(shè)置“查詢緩存”，那么hibernate只會(huì)緩存使用load()方法獲得的單個(gè)持久化對(duì)象，如果想緩存使用findall()、 list()、Iterator()、createCriteria()、createQuery()等方法獲得的數(shù)據(jù)結(jié)果集的話，就需要設(shè)置hibernate.cache.use_query_cache true 才行

2.首先設(shè)置EhCache，建立配置文件ehcache.xml，默認(rèn)的位置在class-path，可以放到你的src目錄下：

?<ehcache>

????<!--?Sets?the?path?to?the?directory?where?cache?.data?files?are?created.

?????If?the?path?is?a?Java?System?Property?it?is?replaced?by
?????its?value?in?the?running?VM.
?????The?following?properties?are?translated:
?????user.home?-?User's?home?directory
?????user.dir?-?User's?current?working?directory
?????java.io.tmpdir?-?Default?temp?file?path?-->
?????<!--<diskStore?path="java.io.tmpdir"/>-->
?????<diskStore?path="/data/ehcache"/>

????<!--Default?Cache?configuration.?These?will?applied?to?caches?programmatically?created?through
????????the?CacheManager.

????????The?following?attributes?are?required:

????????maxElementsInMemory????????????-?Sets?the?maximum?number?of?objects?that?will?be?created?in?memory
????????eternal?????????????????????????????????????-?Sets?whether?elements?are?eternal.?If?eternal,??timeouts?are?
?????????????????????????????????????????? ? ? ? ? ? ?????? ignored?and?the?element?is?never?expired.
????????overflowToDisk??????????????????????-?Sets?whether?elements?can?overflow?to?disk?when?the?in-memory?cache
????????????????????????????????????????????????????????has?reached?the?maxInMemory?limit.

????????The?following?attributes?are?optional:
????????timeToIdleSeconds??????????? -?Sets?the?time?to?idle?for?an?element?before?it?expires.
??????????????????????????????????????????????????????? i.e.?The?maximum?amount?of?time?between?accesses?before?an
???????????????????????? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?? element?expires?Is?only?used?if?the?element?is?not?eternal.
????????????????????????????????????????????????????????Optional?attribute.?A?value?of?0?means?that?an?Element?can?idle
??????????????????????? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ??? for?infinity.The?default?value?is?0.
????????timeToLiveSeconds????????????? -?Sets?the?time?to?live?for?an?element?before?it?expires.
???????????????????????????????????????????????????? ? ? i.e.?The?maximum?time?between?creation?time?and?when?an?element?
?????????????????????????????????????????????????????????expires.??Is?only?used?if?the?element?is?not?eternal.
?????????????????????????????????????????????????????????Optional?attribute.?A?value?of?0?means?that?and?Element?can?live
???????????????????????? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ??? for?infinity.
????????????????????????????????????????????????????????The?default?value?is?0.
????????diskPersistent???????????????????????????-?Whether?the?disk?store?persists?between?restarts?of?the?Virtual
???????????????????????????????????????????????????????????? Machine.
?????????????????????????????????????????????????????????The?default?value?is?false.
????????diskExpiryThreadIntervalSeconds???-?The?number?of?seconds?between?runs?of?the?disk?expiry?thread.?
?????????????????????????????????????????????????????????The?default?value??is?120?seconds.
????????-->

????<defaultCache
????????maxElementsInMemory="10000"
????????eternal="false"
????????overflowToDisk="true"
????????timeToIdleSeconds="120"
????????timeToLiveSeconds="120"
????????diskPersistent="false"
????????diskExpiryThreadIntervalSeconds="120"/>
????<cache?name="org.hibernate.cache.UpdateTimestampsCache"?maxElementsInMemory="5000"?
?????eternal="true"?overflowToDisk="true"/>
????<cache?name="org.hibernate.cache.StandardQueryCache"?maxElementsInMemory="5"?eternal="false"
????timeToLiveSeconds="120"?overflowToDisk="true"/>
????<cache?name="userCache"?maxElementsInMemory="100000"?eternal="false"?timeToIdleSeconds=
??????? "600" ?? timeToLiveSeconds="600"?overflowToDisk="false"?diskPersistent="false"/>
????<cache?name="com.ouou.webapp.util.OuouMethodIntecepter"?maxElementsInMemory="100000"?
????eternal="false"?timeToIdleSeconds="600"?timeToLiveSeconds="600"?overflowToDisk="false"
????diskPersistent="false"/>
????<cache?name="bbcode"?maxElementsInMemory="100000"?eternal="false"?timeToIdleSeconds="600"
????timeToLiveSeconds="600"?
????overflowToDisk="false"?diskPersistent="false"/>
????<cache?name="com.ouou.model.Videos"?maxElementsInMemory="10000"??eternal="false"?
????overflowToDisk="false"?timeToIdleSeconds="120"?timeToLiveSeconds="120"?diskPersistent="false"/>
????<cache?name="com.ouou.model.Tags"?maxElementsInMemory="10000"??eternal="false"
????overflowToDisk="false"?timeToIdleSeconds="120"?timeToLiveSeconds="120"?diskPersistent="false"/>
</ehcache>

以com.ouou.model.Videos為例子
在Videos.hbm.xml中配置：
<class name="Videos" table="TEST" lazy="false">
? <cache usage="read-write" region="ehcache.xml中的name的屬性值"/>注意：這一句需要緊跟在class標(biāo)簽下面，其他位置無(wú)效。
hbm文件查找cache方法名的策略：如果不指定hbm文件中的region="ehcache.xml中的name的屬性值"，則使用name名為com.ouou.model.Videos的cache，
如果不存在與類名匹配的cache名稱，則用defaultCache。
如果Videos包含set集合，則需要另行指定其cache
例如Videos包含Tags集合，則需要
添加如下配置到ehcache.xml中
<cache name="com.ouou.model.Tags"
??????? maxElementsInMemory="10000" eternal="false" timeToIdleSeconds="120"
??????? timeToLiveSeconds="120" overflowToDisk="false" />
另，針對(duì)查詢緩存的配置如下：
<cache name="org.hibernate.cache.UpdateTimestampsCache"
??????? maxElementsInMemory="5000"
??????? eternal="true"
??????? overflowToDisk="true"/>
<cache name="org.hibernate.cache.StandardQueryCache"
??????? maxElementsInMemory="10000"
??????? eternal="false"
??????? timeToLiveSeconds="120"
??????? overflowToDisk="true"/>

3、 選擇緩存策略依據(jù)：

<cache? usage="transactional|read-write|nonstrict-read-write|read-only" (1)/>
ehcache不支持transactional，其他三種可以支持。
read-only：無(wú)需修改， 那么就可以對(duì)其進(jìn)行只讀 緩存，注意，在此策略下，如果直接修改數(shù)據(jù)庫(kù)，即使能夠看到前臺(tái)顯示效果，
但是將對(duì)象修改至cache中會(huì)報(bào)error，cache不會(huì)發(fā)生作用。另：刪除記錄會(huì)報(bào)錯(cuò)，因?yàn)椴荒茉趓ead-only模式的對(duì)象從cache中刪除。
read-write：需要更新數(shù)據(jù)，那么使用讀/寫(xiě)緩存 比較合適，前提：數(shù)據(jù)庫(kù)不可以為serializable transaction isolation level
（序列化事務(wù)隔離級(jí)別）
nonstrict-read-write：只偶爾需要更新數(shù)據(jù)（也就是說(shuō)，兩個(gè)事務(wù)同時(shí)更新同一記錄的情況很不常見(jiàn)），也不需要十分嚴(yán)格的事務(wù)隔離，
那么比較適合使用非嚴(yán)格讀/寫(xiě)緩存策略。

4、 調(diào)試時(shí)候使用log4j的log4j.logger.org.hibernate.cache=debug，更方便看到ehcache的操作過(guò)程，主要用于調(diào)試過(guò)程,實(shí)際應(yīng)用發(fā)布時(shí)候，請(qǐng)注釋掉，以免影響性能。

5、 使用ehcache，打印sql語(yǔ)句是正常的，因?yàn)閝uery cache設(shè)置為true將會(huì)創(chuàng)建兩個(gè)緩存區(qū)域：一個(gè)用于保存查詢結(jié)果集 (
org.hibernate.cache.StandardQueryCache)；另一個(gè)則用于保存最近查詢的一系列表的時(shí)間戳(org.hibernate.cache.UpdateTimestampsCache)。
請(qǐng)注意：在查詢緩存中，它并不緩存結(jié)果集中所包含的實(shí)體的確切狀態(tài)；它只緩存這些實(shí)體的標(biāo)識(shí)符屬性的值、以及各值類型的結(jié)果。
需要將打印sql語(yǔ)句與最近的cache內(nèi)容相比較，將不同之處修改到cache中，所以查詢緩存通常會(huì)和二級(jí)緩存一起使用。