<?xml version="1.0" encoding="GBK"?>
<ehcache>
<diskStore path="D:\\TempObject"/>
<defaultCache
maxElementsInMemory="10000"
eternal="false"
timeToIdleSeconds="100"
timeToLiveSeconds="1000"
overflowToDisk="true"
/>
<cache name="com.sitechasia.occ.core.base.ExampleForTest" maxElementsInMemory="10000"
eternal="false"
timeToIdleSeconds="100"
timeToLiveSeconds="1000"
overflowToDisk="true"
/>
</ehcache>
建議自定義cache時，cache名字和類路徑名相同。
（1）不要使用默認緩存策略defaultCache（多個class共享）
（2）不要
給cache name另外起名
否則繼承AbstractTransactionalDataSourceSpringContextTests做測試時，拋出
org.hibernate.cache.CacheException: java.lang.IllegalStateException: The com.sitechasia.occ.core.base.ExampleForTest Cache is not alive.（我注釋了
紅色的cache，使用defaultCache導致）
2.在ExampleForTest.hbm.xml中添加：（如果有集合，也需要添加）
<hibernate-mapping>
<class name="com.sitechasia.occ.core.base.ExampleForTest"
table="TESTTABLE" lazy="false">
<cache usage="read-write"/>
<id name="id" type="java.lang.String">
<column name="id" length="32" />
<generator class="uuid"></generator>
</id>
<property name="field1" type="java.lang.String" />
<property name="field2" type="java.lang.String" />
</class>
</hibernate-mapping>
如果使用Annocation，則類前添加
@Cache(usage = CacheConcurrencyStrategy.READ_WRITE)
@Proxy(lazy = false)
3.在spring.xml中添加：
<property name="hibernateProperties">
<props>
<prop key="hibernate.dialect">${hibernate.dialect}</prop>
<prop key="hibernate.show_sql">true</prop>
<!--
使用hibernate自帶cache，適合測試用
<prop key="hibernate.cache.provider_class">
org.hibernate.cache.HashtableCacheProvider
</prop>
-->
<!--
使用ehcache，適合項目用 -->
<prop key="hibernate.cache.provider_class">
org.hibernate.cache.EhCacheProvider
</prop>
<!--
打開hibernate統(tǒng)計功能，我們測試中使用hibernate的統(tǒng)計類-->
<prop key="hibernate.generate_statistics">true</prop>
<!--
最優(yōu)化二級緩存-->
<prop key="hibernate.cache.use_structured_entries">
true
</prop>
<!--
完全禁用二級緩存開關(guān)，對那些在類的映射定義中指定cache的類，默認開啟二級緩存-->
<prop key="cache.use_second_level_cache">true</prop>
<!-- prop key="hibernate.hbm2ddl.auto">create</prop>
<prop key="hibernate.default_schema">
${dbunit.schema}
</prop>
-->
</props>
</property>
4.配置完了，我們可以測試了：
測試類繼承spring的測試組件AbstractTransactionalDataSourceSpringContextTests類；
先初始化數(shù)據(jù)：
private ExampleForTest example1, example2;
public void onSetUpBeforeTransaction() {
example1 = new ExampleForTest();
example1.setField1("param1");
example1.setField2("param2");
example2 = new ExampleForTest();
example2.setField1("attribute1");
example2.setField2("attribute2");
}
再寫測試方法：
exampleDao中有2個方法：
（1）list方式獲取參數(shù)：（對二級緩存只寫不讀）
exampleDao.findByHQL(hql);
（2）iterate方式獲取參數(shù)：（對二級緩存可寫可讀）
exampleDao.cacheByHQL(hql);
測試（2）方法：
public void testCacheByHQL() {
/**先打開注釋，往數(shù)據(jù)庫增加2條數(shù)據(jù)，然后關(guān)閉
exampleDao.save(example1);
exampleDao.save(example2);
setComplete();
*/
String hql = "from ExampleForTest";
//List list = exampleDao.findByHQL(hql);
//開關(guān)控制
List<ExampleForTest> iterate = exampleDao.cacheByHQL(hql);
Statistics statistics = sessionFactory.getStatistics();
// 統(tǒng)計entity信息
for (int i = 0; i < statistics.getEntityNames().length; i++) {
String entityName = statistics.getEntityNames()[i];
System.out.println("entityName:" + entityName);
EntityStatistics entityStatistics = statistics
.getEntityStatistics(entityName);
System.out.println("entityStatistics:" + entityStatistics);
}
assertEquals(2, iterate.size());
}
1》注釋開關(guān)控制代碼行，iterate獲取數(shù)據(jù)，發(fā)現(xiàn)有N+1問題，說明是從數(shù)據(jù)庫讀取的數(shù)據(jù)，日志如下：
Hibernate: select examplefor0_.id as col_0_0_ from TESTTABLE examplefor0_
Hibernate: select examplefor0_.id as id0_0_, examplefor0_.field1 as field2_0_0_, examplefor0_.field2 as field3_0_0_ from TESTTABLE examplefor0_ where examplefor0_.id=?
Hibernate: select examplefor0_.id as id0_0_, examplefor0_.field1 as field2_0_0_, examplefor0_.field2 as field3_0_0_ from TESTTABLE examplefor0_ where examplefor0_.id=?
entityName:com.sitechasia.occ.core.base.ExampleForTest
entityStatistics:EntityStatistics[
loadCount=2,updateCount=0,insertCount=0,deleteCount=0,
fetchCount=2,optimisticLockFailureCount=0]
2》打開開關(guān)控制代碼行注釋，先list方式讀取數(shù)據(jù)，會寫入二級緩存，再用iterate獲取數(shù)據(jù)時，發(fā)現(xiàn)沒有了N+1問題，說明是從二級緩存中讀取的數(shù)據(jù)，日志如下：
Hibernate: select examplefor0_.id as id0_, examplefor0_.field1 as field2_0_, examplefor0_.field2 as field3_0_ from TESTTABLE examplefor0_
Hibernate: select examplefor0_.id as col_0_0_ from TESTTABLE examplefor0_
entityName:com.sitechasia.occ.core.base.ExampleForTest
entityStatistics:EntityStatistics[
loadCount=2,updateCount=0,insertCount=0,deleteCount=0,fetchCount=0,optimisticLockFailureCount=0]
5.需要注意的是，實體映射文件中l(wèi)azy=false必須設置，即立即加載；否則后臺日志不打印那N條通過id獲取實體的sql，無法判斷是否使用二級緩存。