在上篇《》中我们使用Hibernate作为ORM的框架，直接调用Hibernate的API进行相关的持久化操作，但在实际项目中，可能会由于公司规定等原因要求统一使用JPA接口来进行持久化，而JPA的实现可以灵活配置，避免对第三方JPA实现的过分依赖，这样可能会牺牲第三方JPA实现带来的一些额外优化和特性，但确实避免了对其依赖，本文将更改《》Demo的实现，使其使用JPA标准接口进行持久化操作，而JPA实现可以配置为Hibernate或EclipseLink支持。

　　第一步：将HibernateConfiguration类修改为JpaConfiguration类

1 @Configuration 2 public class JpaConfiguration { 3     @Autowired 4     private DataSource dataSource; 5     @Bean 6     public Map
     
       jpaProperties() { 7         Map
      
        props = new HashMap
       
        (); 8         //Hibernate JPA properties 9             10         /*props.put("hibernate.dialect", H2Dialect.class.getName());11         props.put("hibernate.cache.provider_class", HashtableCacheProvider.class.getName());*/12             13         //EclipseLink JPA properties14             15         props.put("eclipselink.weaving", "false");    16             17         return props;18     }19     @Bean20     public JpaVendorAdapter jpaVendorAdapter() {      21         //Hibernate JPA Vendor Adapter22         /*AbstractJpaVendorAdapter jpaVendorAdapter = new HibernateJpaVendorAdapter();*/23             24         //EclipseLink JPA Vendor Adapter25         AbstractJpaVendorAdapter jpaVendorAdapter = new EclipseLinkJpaVendorAdapter();26              27         //Common vendor settings28         jpaVendorAdapter.setShowSql(false);29         jpaVendorAdapter.setGenerateDdl(true);30         jpaVendorAdapter.setDatabase(Database.H2);//指定数据库为 H231              32         return jpaVendorAdapter;      33     }34     @Bean35     public PlatformTransactionManager transactionManager() {36         return new JpaTransactionManager( localContainerEntityManagerFactoryBean().getObject() );37     }38     @Bean39     public LocalContainerEntityManagerFactoryBean localContainerEntityManagerFactoryBean() {40         LocalContainerEntityManagerFactoryBean lef = new LocalContainerEntityManagerFactoryBean();41         lef.setLoadTimeWeaver(new InstrumentationLoadTimeWeaver());42         lef.setDataSource(this.dataSource);43         lef.setJpaPropertyMap(this.jpaProperties());44         lef.setJpaVendorAdapter(this.jpaVendorAdapter());45         return lef;46     }47         48     /**49      * 设置数据源，可以指定类型为Derby或HSQLDB50      * @return51      */52     @Bean53     public DataSource dataSource(){54         EmbeddedDatabaseBuilder builder = new EmbeddedDatabaseBuilder();55         builder.setType(EmbeddedDatabaseType.H2);56         return builder.build();57     }58 }
       
      
     

　　第二步：修改OrderPersistenceTests类

　　将org.hibernate.Session类的API操作修改为javax.persistence.EntityManager类的API

　　org.hibernate.Session类的API代码示例：

1 @Autowired 2     private SessionFactory sessionFactory; 3     @Test 4     @Transactional 5     public void testSaveOrderWithItems() throws Exception { 6         Session session = sessionFactory.getCurrentSession(); 7         Order order = new Order(); 8         order.getItems().add(new Item()); 9         session.save(order);10         session.flush();11         assertNotNull(order.getId());12     }

　　javax.persistence.EntityManager类的API代码示例：

1 @PersistenceContext 2     private EntityManager entityManager; 3     @Test 4     @Transactional 5     public void testSaveOrderWithItems() throws Exception { 6         Order order = new Order(); 7         order.getItems().add(new Item()); 8         entityManager.persist(order); 9         entityManager.flush();10         assertNotNull(order.getId());11     }

　　第三步：修改Maven依赖

　　修改完成，可以开始运行测试用例进行调试！总感觉EclipseLink是个半成品，不是很好使，甲骨文公司还是希望Everybody使用TopLink！