我是hibernate和spring的新手，我尝试使用hibernate二级缓存。但它似乎不起作用。我有一个以下测试类：
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = { "classpath:applicationContext.xml" })
@TransactionConfiguration
@Transactional
public class CacheTest extends AbstractTransactionalJUnit4SpringContextTests
{
@Test
public void testCache1()
{
System.out.println("Running testCache1");
ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
MutableDAO<AppUser> appUserDAO = new MutableDAOImpl<AppUser>(AppUser.class, (SessionFactory) ctx.getBean("OnMediaSessionFactory"), 10);
assertNotNull("AppUser DAO is null.", appUserDAO);
SessionFactory sessionFactory = (SessionFactory)ctx.getBean("OnMediaSessionFactory");
long numberOfUsers = appUserDAO.countAll();
System.out.println("Number of rows :" + numberOfUsers);
final String cacheRegion = AppUser.class.getCanonicalName();
SecondLevelCacheStatistics settingsStatistics = sessionFactory.getStatistics().
getSecondLevelCacheStatistics(cacheRegion);
StopWatch stopWatch = new StopWatch();
stopWatch.start();
appUserDAO.findAll();
stopWatch.stop();
System.out.println("Query time : " + stopWatch.getTotalTimeSeconds());
System.out.println(settingsStatistics);
}
@Test
public void testCache2()
{
System.out.println("Running testCache2");
ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
MutableDAO<AppUser> appUserDAO = new MutableDAOImpl<AppUser>(AppUser.class, (SessionFactory) ctx.getBean("OnMediaSessionFactory"), 10);
assertNotNull("AppUser DAO is null.", appUserDAO);
SessionFactory sessionFactory = (SessionFactory)ctx.getBean("OnMediaSessionFactory");
long numberOfUsers = appUserDAO.countAll();
System.out.println("Number of rows :" + numberOfUsers);
final String cacheRegion = AppUser.class.getCanonicalName();
SecondLevelCacheStatistics settingsStatistics = sessionFactory.getStatistics().
getSecondLevelCacheStatistics(cacheRegion);
StopWatch stopWatch = new StopWatch();
stopWatch.start();
appUserDAO.findAll();
stopWatch.stop();
System.out.println("Query time : " + stopWatch.getTotalTimeSeconds());
System.out.println(settingsStatistics);
}
}
我有
<prop key="hibernate.show_sql">false</prop>
<prop key="hibernate.format_sql">true</prop>
<prop key="hibernate.use_sql_comments">true</prop>
<prop key="hibernate.cache.use_query_cache">true</prop>
<prop key="hibernate.cache.use_second_level_cache">true</prop>
<prop key="hibernate.generate_statistics">true</prop>
<prop key="hibernate.cache.use_structured_entries">true</prop>
但我输出如下：
Running testCache1
Number of rows :81
Query time : 0.129
SecondLevelCacheStatistics[hitCount=0,missCount=0,putCount=81,elementCountInMemory=81,elementCountOnDisk=0,sizeInMemory=219634]
Running testCache2
Number of rows :81
Query time : 0.063
SecondLevelCacheStatistics[hitCount=0,missCount=0,putCount=81,elementCountInMemory=81,elementCountOnDisk=0,sizeInMemory=219634]
我需要做些什么才能让它发挥作用？
答案 0 :(得分：3)
您的测试看起来很奇怪，您为每个测试创建了一个新的应用程序上下文，因此Hibernate SessionFactory无法在测试之间以及二级缓存中存活。
正确的测试看起来像这样：
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = { "classpath:applicationContext.xml" })
public class CacheTest extends AbstractTransactionalJUnit4SpringContextTests
{
@Autowired
private MutableDAO<AppUser> appUserDAO;
@Autowired
private SessionFactory sessionFactory;
private TransactionTemplate tx;
@Autowired
public void setPtm(PlatformTransactionManagement ptm) {
tx = new TransactionTemplate(ptm);
}
@Test
public void doTestCache() {
// Using programmatic transaction management since we need 2 transactions
// inside the same method
// 1st attempt
tx.execute(new TransactionCallbackWithoutResult() {
public void doInTransactionWithoutResult(TransactionStatus status) {
testCache();
}
});
// 2nd attempt
tx.execute(new TransactionCallbackWithoutResult() {
public void doInTransactionWithoutResult(TransactionStatus status) {
testCache();
}
});
}
public void testCache() {
long numberOfUsers = appUserDAO.countAll();
System.out.println("Number of rows :" + numberOfUsers);
final String cacheRegion = AppUser.class.getCanonicalName();
SecondLevelCacheStatistics settingsStatistics = sessionFactory.getStatistics().
getSecondLevelCacheStatistics(cacheRegion);
StopWatch stopWatch = new StopWatch();
stopWatch.start();
appUserDAO.findAll();
stopWatch.stop();
System.out.println("Query time : " + stopWatch.getTotalTimeSeconds());
System.out.println(settingsStatistics);
}
}
答案 1 :(得分：2)
首先，请记住，Hibernate默认情况下不使用任何缓存提供程序。因此，您需要一个用于Hibernate的2L缓存的“外部”缓存提供程序。对于我的回答，我将使用ehcache和Hibernate 3.3。请注意，在更新版本的Hibernate中更改了配置，因此，请阅读您正在使用的确切版本的文档。
在你的Hibernate配置中，你错过了一个部分，即将Hibernate指向实际的提供者。属性hibernate.cache.provider_class为Hibernate 3.3执行此操作。将其值设置为net.sf.ehcache.hibernate.SingletonEhCacheProvider
现在，您还需要一个ehcache.xml，如下所示：
<?xml version="1.0" encoding="UTF-8"?>
<ehcache>
<diskStore path="./cache" />
<defaultCache maxElementsInMemory="10000"
eternal="true"
overflowToDisk="true"
diskPersistent="true"
diskExpiryThreadIntervalSeconds="120"
memoryStoreEvictionPolicy="FIFO" />
<cache name="com.mycompany.jpa.MyEntity"
maxElementsInMemory="50"
overflowToDisk="true" />
<cache name="org.hibernate.cache.StandardQueryCache"
maxElementsInMemory="50"
overflowToDisk="true" />
<cache name="org.hibernate.cache.UpdateTimestampsCache"
maxElementsInMemory="5000"
overflowToDisk="true" />
</ehcache>
你没有展示你的DAO，所以，我不确定它是否正确。请注意，您始终需要明确缓存，因为它意味着使用特定位置的解决方案，而不是一切的通用解决方案。这意味着，在您的DAO中，您将添加一个查询提示，指出您的查询是可缓存的（从您的测试中，您似乎需要查询缓存，而不仅仅是实体缓存）。
如果仍然无法使其正常工作，请参阅以下JIRA中的附件。它包含一个启用了缓存的maven项目，因此，您可以将其与您的代码进行比较：