Java 如何使用 entityManager 在 JPA 中启动事务
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How to start a transaction in JPA using entityManager
提问by azaveri7
I have started working on an application which uses spring, hibernate, JPA, SOAP webservices. Now there is a requirement that certain queries have to be run in a transaction. If any one fails, entire transaction should rollback.
我已经开始开发一个使用 spring、hibernate、JPA、SOAP 网络服务的应用程序。现在要求某些查询必须在事务中运行。如果任何一个失败，整个事务应该回滚。
The code in the dao layer is as follows :
dao层的代码如下：
import javax.persistence.EntityManager;
import javax.persistence.EntityTransaction;
import javax.persistence.PersistenceContext;
import javax.persistence.PersistenceContextType;
import javax.persistence.Query;
import org.hibernate.Session;
public class BillDAOImpl implements BillDao{
@PersistenceContext(type = PersistenceContextType.EXTENDED)
private EntityManager em;
public boolean processBills() throws Exception{
EntityTransaction tx = null;
Session session = null;
try{
session = em.unwrap(Session.class);
tx = em.getTransaction();
Bill bill = em.find(Bill.class, billId);
//session.beginTransaction();
tx.begin();
...
...
em.persist(bill);
...
...
em.merge(<other object>);
...
...
//session.getTransaction().commit();
tx.commit();
} catch(){
}
}
}
When it executes tx = em.getTransaction(), it gives following error :
当它执行时tx = em.getTransaction()，它给出以下错误：
java.lang.IllegalStateException: Cannot execute getTransaction() on a container-managed EntityManager
The other transaction related properties are as follows :
其他与交易相关的属性如下：
<bean id="tuneEntityManagerFactory"
class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"
p:persistenceXmlLocation="classpath*:META-INF/tune-persistence.xml"
p:persistenceUnitName="tunePersistenceUnit" p:loadTimeWeaver-ref="loadTimeWeaver"
p:jpaVendorAdapter-ref="jpaVendorAdapter" p:jpaDialect-ref="jpaDialect"
p:dataSource-ref="tuneDbDataSource">
<property name="jpaProperties">
<props>
<prop key="hibernate.transaction.manager_lookup_class">org.hibernate.transaction.BTMTransactionManagerLookup
</prop>
<prop key="net.sf.ehcache.configurationResourceName">/${tune-db.ehcache.config.file}</prop>
<prop key="hibernate.transaction.flush_before_completion">false</prop>
<prop key="hibernate.default_schema">${tune-db.schema}</prop>
<prop key="org.hibernate.envers.default_schema">${tune-db.schema}</prop>
<prop key="javax.persistence.validation.mode">${tune-db.data.validation}</prop>
<prop key="hibernate.connection.isolation">3</prop>
<prop key="hibernate.connection.release_mode">auto</prop>
<prop key="hibernate.show_sql">${tune-db.hibernate.show-sql}</prop>
<prop key="hibernate.format_sql">${tune-db.hibernate.format-sql}</prop>
</props>
</property>
</bean>
<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
<property name="entityManagerFactory" ref="tuneEntityManagerFactory" />
</bean>
When I use session.beginTransaction()and session.getTransaction().commit(), it works correctly.
当我使用session.beginTransaction()and 时session.getTransaction().commit()，它工作正常。
However I want to replace it with transaction from entityManager. Then what should be done?
但是我想用来自entityManager. 那应该怎么办呢？
回答by Maciej Kowalski
Try injecting EntityManagerFactory and then creating the EntityManager manually:
尝试注入 EntityManagerFactory，然后手动创建 EntityManager：
@PersistenceUnit
private EntityManagerFactory entityManagerFactory;
public boolean processBills() throws Exception{
EntityManager em = entityManagerFactory.createEntityManager();
EntityTransaction tx = null;
Session session = null;
try{
session = em.unwrap(Session.class);
tx = em.getTransaction();
回答by yaswanth
@Transactional annotation will do exactly what you need.
@Transactional 注释将完全满足您的需求。
回答by userJ
The EntityManager instance returned by @PersistenceContext is always a container managed EntityManager. And container managed EntityManager are always JTA EntityManagers and hence their lifecycle is managed by the container. I guess now it makes sense as to why it is illegal to call getTransaction() on them.This might help
@PersistenceContext 返回的 EntityManager 实例始终是容器管理的 EntityManager。容器管理的 EntityManager 始终是 JTA EntityManager，因此它们的生命周期由容器管理。我想现在可以解释为什么对它们调用 getTransaction() 是非法的了。这可能有帮助
回答by coladict
The add a hibernate.jta.allowTransactionAccessproperty with the value trueand you should be allowed to use it manually. Though it's not a good practice to mix your strategies, having some code managed by JTA, some manually.
添加hibernate.jta.allowTransactionAccess具有该值的属性，true您应该被允许手动使用它。虽然混合您的策略不是一个好习惯，有一些代码由 JTA 管理，一些手动。
