我在事务方面遇到问题,因为使用 @Transactional 注释调用 DAO 的服务会引发异常,表明 session 未打开。我让它工作的唯一方法是使用 @Transactional 注释 DAO。到底发生了什么?
这是我想做的,但不起作用:
class CustomerService {
private CustomerDao dao;
@Transactional
public void foo() {
int customerId = dao.getCustomer("fred");
}
}
class CustomerDao {
private HibernateTemplate hibernateTemplate;
public int getCustomer(String name) {
String sql = "SELECT {m.*} from Customers {m} where name=:name";
Query qry = getSession().createSQLQuery(sql).addEntity("m", Customer.class);
qry.setParameter("name", name);
qry.setCacheable(false);
List<Customer> list = qry.list();
return list.iterator().next().getId();
}
private Session getSession() {
return hibernateTemplate.getSessionFactory().getCurrentSession();
}
}
这就是我正在做的事情,但我不想这样做:
class CustomerService {
private CustomerDao dao;
public Customer(CustomerDao dao) {
this.dao = dao;
}
public void foo() {
int customerId = dao.getCustomer("fred");
}
}
class CustomerDao {
private HibernateTemplate hibernateTemplate;
@Transactional
public int getCustomer(String name) {
String sql = "SELECT {m.*} from Customers {m} where name=:name";
Query qry = getSession().createSQLQuery(sql).addEntity("m", Customer.class);
qry.setParameter("name", name);
qry.setCacheable(false);
List<Customer> list = qry.list();
return list.iterator().next().getId();
}
private Session getSession() {
return hibernateTemplate.getSessionFactory().getCurrentSession();
}
}
问题似乎是由在包装器类的构造函数内实例化 CustomerService 引起的,其中包装器是在 Spring xml 上下文文件中声明的:
class AllServices {
private final CustomerService customerService;
private final OrderService orderService;
@Autowired
public AllServices(CustomerDao customerDao, OrderDao orderDao) {
this.customerService = new CustomerService(customerDao);
this.orderService = new OrderService(orderDao);
}
public CustomerService getCustomerService() {
return this.customerService;
}
public OrderService getOrderService() {
return this.orderService;
}
}
spring 文件如下所示:
<context:annotation-config />
<import resource="classpath:db-spring-conf.xml"/>
<bean id="allServices" class="myPackage.AllServices" />
和 db-spring-conf:
<bean id="editorDatasource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName" value="com.mysql.jdbc.Driver" />
<property name="url" value="${versioning.db}" />
<property name="username" value="${versioning.user}" />
<property name="password" value="${versioning.pass}" />
</bean>
<tx:annotation-driven transaction-manager="editorTransactionManager"/>
<bean id="editorSessionFactory" class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean">
<property name="dataSource" ref="editorDatasource"/>
<property name="exposeTransactionAwareSessionFactory">
<value>true</value>
</property>
<property name="annotatedClasses">
<list>
<value>myPackage.Order</value>
</list>
</property>
<property name="mappingResources">
<list>
<value>mappings/customer.hbm.xml</value>
</list>
</property>
<property name="hibernateProperties">
<props>
<prop key="hibernate.dialect">org.hibernate.dialect.MySQLDialect</prop>
<prop key="hibernate.show_sql">true</prop>
<prop key="hibernate.hbm2ddl.auto">validate</prop>
<!-- Enable Query Cache -->
<prop key="hibernate.cache.use_query_cache">false</prop>
<!-- Enable 2nd Level Cache -->
<prop key="hibernate.cache.use_second_level_cache">false</prop>
<prop key="hibernate.connection.autocommit">false</prop>
<prop key="hibernate.current_session_context_class">org.springframework.orm.hibernate3.SpringSessionContext</prop>
</props>
</property>
</bean>
<bean id="editorHibernateTemplate" class="org.springframework.orm.hibernate3.HibernateTemplate">
<property name="sessionFactory" ref="editorSessionFactory"/>
</bean>
<bean id="editorTransactionManager" class="org.springframework.orm.hibernate3.HibernateTransactionManager">
<property name="sessionFactory" ref="editorSessionFactory" />
</bean>
<!-- DAOs -->
<bean id="customerDao" class="myPackage.CustomerHibernateDao" />
<bean id="orderDao" class="myPackage.OrderHibernateDao" />
我现在已经将 CustomerService 的实例化移到了 Spring 配置文件中,一切都很顺利。所有使用 @Transactional 的类都必须位于上下文文件中吗?另外,为了使其工作,我必须为 CustomerService 创建一个接口(interface),以防止加载上下文文件时出现异常 - 无法生成类的 CGLIB 子类
最佳答案
所以,您确定了问题的原因 - Spring 的 @Transactional
支持是一个切面,Spring 中的切面仅应用于由 Spring 容器管理的组件(尽管它是 can be changed ,但是这是针对复杂情况的高级功能)。
如果您不喜欢在 XML 中声明服务,您可以查看 delcare Spring 管理的组件的其他选项:
- Classpath scanning
- Java-based configuration (自 Spring 3.x 起)
关于 CGLIB 代理的问题,请参阅 7.6 Proxying mechanisms - 可能您的类路径中没有 CGLIB 实现。
关于java - 除非在 DAO 内部,否则交易无法进行,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/3670152/