Hibernate OSCache 配置示例教程

原文： https://howtodoinjava.com/hibernate/hibernate-oscache-configuration-example-tutorial/

OSCache 是 OpenSymphony 开发的 Java 框架，可轻松在 Web 应用中缓存内容。 使用 Hiberate ，可以将其配置为充当二级缓存 。

在我的前一篇文章中，我们了解了为 Hiberate 配置 EhCache 的过程，这是 Hiberate 中的默认二级缓存。 在本文中，我以使用 Hiberate 配置 OSCache 为例。

Sections in this post: 
Runtime dependencies
Hibernate configuration
In memory cache example
Physical cache example

运行时依赖项

我已经使用 Maven 来管理项目依赖项，并且pom.xml文件中的必要补充是：

<repositories>
    <repository>
      <id>repository.jboss.org-public</id>
      <name>JBoss.org Maven repository</name>
      <url>https://repository.jboss.org/nexus/content/groups/public</url>
    </repository>  
</repositories>
<!-- OSCache dependencies -->
<dependency>
    <groupId>opensymphony</groupId>
    <artifactId>oscache</artifactId>
    <version>2.4.1</version>
</dependency>
<dependency>
  <groupId>javax.jms</groupId>
  <artifactId>jms</artifactId>
  <version>1.1</version>
</dependency>

如果您不使用 maven，则在项目构建路径中添加相应的 jar 文件。

Hiberate 配置

在项目中配置 OSCache 的唯一更改是，必须在 Hiberate 配置文件中创建 hibernate.cfg.xml文件：

    <!-- Cache provider class -->
    <property name="hibernate.cache.provider_class">org.hibernate.cache.OSCacheProvider</property>

内存中的缓存示例

这是默认实现，如果未配置物理缓存属性，则会得到它。 让我们看一下测试代码示例：

    try
    {
        //Open the hibernate session
        Session session = HibernateUtil.getSessionFactory().openSession();
        session.beginTransaction();
        //fetch the department entity from database first time
        DepartmentEntity department = (DepartmentEntity) session.load(DepartmentEntity.class, new Integer(1));
        System.out.println(department.getName());
        //fetch the department entity again; Fetched from first level cache
        department = (DepartmentEntity) session.load(DepartmentEntity.class, new Integer(1));
        System.out.println(department.getName());
        //Let's close the session
        session.getTransaction().commit();
        session.close();
        //Try to get department in new session
        Session anotherSession = HibernateUtil.getSessionFactory().openSession();
        anotherSession.beginTransaction();
        //Here entity is already in second level cache so no database query will be hit
        department = (DepartmentEntity) anotherSession.load(DepartmentEntity.class, new Integer(1));
        System.out.println(department.getName());
        anotherSession.getTransaction().commit();
        anotherSession.close();
    }
    finally
    {
        System.out.println(HibernateUtil.getSessionFactory().getStatistics().getEntityFetchCount()); //Prints 1
        System.out.println(HibernateUtil.getSessionFactory().getStatistics().getSecondLevelCacheHitCount()); //Prints 1
        HibernateUtil.shutdown();
    }
    Output in console:
    Hibernate: insert into DEPARTMENT (NAME) values (?)
    Hibernate: select department0_.ID as ID0_0_, department0_.NAME as NAME0_0_ from DEPARTMENT department0_ where department0_.ID=?
    Human Resource
    Human Resource
    Human Resource
    1
    1

您将一次又一次地获得此输出，因为每次关闭 Hiberate 时，都会刷新内存并在下次运行时构建二级缓存。

物理缓存示例

如果您要构建的缓存非常大，则最好在文件系统中构建它（例如 Windows 中的 C 驱动器）。 这将防止 Hiberate 在每次重新启动应用时建立高速缓存。 同样，二级缓存提取规则仍然适用。

要启用物理缓存，请下载oscache.properties文件，并取消注释以下几行：

cache.memory=false
cache.persistence.class=com.opensymphony.oscache.plugins.diskpersistence.DiskPersistenceListener
cache.path=c:/temp/cache
cache.algorithm=com.opensymphony.oscache.base.algorithm.LRUCache

让我们看一下测试代码示例：

    try
    {
        //Open the hibernate session
        Session session = HibernateUtil.getSessionFactory().openSession();
        session.beginTransaction();
        //fetch the department entity from database first time
        DepartmentEntity department = (DepartmentEntity) session.load(DepartmentEntity.class, new Integer(1));
        System.out.println(department.getName());
        //fetch the department entity again; Fetched from first level cache
        department = (DepartmentEntity) session.load(DepartmentEntity.class, new Integer(1));
        System.out.println(department.getName());
        //Let's close the session
        session.getTransaction().commit();
        session.close();
        //Try to get department in new session
        Session anotherSession = HibernateUtil.getSessionFactory().openSession();
        anotherSession.beginTransaction();
        //Here entity is already in second level cache so no database query will be hit
        department = (DepartmentEntity) anotherSession.load(DepartmentEntity.class, new Integer(1));
        System.out.println(department.getName());
        anotherSession.getTransaction().commit();
        anotherSession.close();
    }
    finally
    {
        System.out.println(HibernateUtil.getSessionFactory().getStatistics().getEntityFetchCount()); //Prints 1
        System.out.println(HibernateUtil.getSessionFactory().getStatistics().getSecondLevelCacheHitCount()); //Prints 1
        HibernateUtil.shutdown();
    }
    Output in console:
    Hibernate: insert into DEPARTMENT (NAME) values (?)
    Hibernate: select department0_.ID as ID0_0_, department0_.NAME as NAME0_0_ from DEPARTMENT department0_ where department0_.ID=?
    Human Resource
    Human Resource
    Human Resource
    1
    1

上面的代码将在“c:/tempcache”位置创建物理缓存。

下次再次运行示例代码时，将获得以下输出：

    Hibernate: insert into DEPARTMENT (NAME) values (?)
    Human Resource
    Human Resource
    Human Resource
    0
    2

将部门实体存储在物理二级缓存中并从那里获取的原因很简单。 因此 Hiberate 将不会再次进入数据库。

要下载该项目的源代码，请遵循给定的链接。

祝您学习愉快！