Spring+Hibernate配置中获取EntityManager

Obtaining EntityManager in Spring + Hibernate configuration

提问by Alex

I have a Spring MVC 4.0 application, and I am learning JPA. I use Hibernate as the JPA implementation.

我有一个 Spring MVC 4.0 应用程序，我正在学习 JPA。我使用 Hibernate 作为 JPA 实现。

I can configure Hibernate as described in thistutorial. It works fine, but I have to use Hibernate's Sessionobject:

我可以按照本教程中的描述配置 Hibernate 。它工作正常，但我必须使用 Hibernate 的Session对象：

@Autowired
SessionFactory sessionFactory;

...

Session session = sessionFactory.openSession();

Now, I want to use JPA's EntityManagerinstead. I have followed thistutorial on the same web site (the configuration is very similar). And I tried to obtain an EntityManagerobject this way:

现在，我想改用 JPA EntityManager。我在同一个网站上遵循了本教程（配置非常相似）。我试图通过EntityManager这种方式获得一个对象：

@PersistenceContext
EntityManager entityManager;

I got a runtime message:

我收到一条运行时消息：

java.lang.IllegalStateException: No transactional EntityManager available

Then, I followed the suggestion in thisanswer, and tried to use the following code:

然后，我遵循了这个答案中的建议，并尝试使用以下代码：

@PersistenceContext
EntityManager entityManager;

...

entityManager=entityManager.getEntityManagerFactory().createEntityManager();

It works a few times (about 9 repetitive method invocations), and then the application freezes.

它工作了几次（大约 9 次重复的方法调用），然后应用程序冻结。

What is the right way to get EntityManagerin Spring + Hibernate configuration?

EntityManager进入 Spring + Hibernate 配置的正确方法是什么？

I do not need any Spring transaction functionality for now. I just want to get an access to EntityManagerand play with JPA.

我现在不需要任何 Spring 事务功能。我只想访问EntityManager并使用 JPA。

Spring/Hibernate configuration file (hibernate.xml)

Spring/Hibernate 配置文件 (hibernate.xml)

<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:tx="http://www.springframework.org/schema/tx"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd
        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.0.xsd">

    <bean id="dataSource" class="org.apache.tomcat.dbcp.dbcp.BasicDataSource">
        <property name="driverClassName" value="com.mysql.jdbc.Driver" />
        <property name="url" value="jdbc:mysql://localhost:3306/test_db" />
        <property name="username" value="test" />
        <property name="password" value="test" />
    </bean>

    <bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
        <property name="dataSource" ref="dataSource" />
        <property name="packagesToScan" value="net.myproject" />
        <property name="jpaVendorAdapter">
            <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter" />
        </property>
        <property name="jpaProperties">
            <props>
                <prop key="hibernate.hbm2ddl.auto">update</prop>
                <prop key="hibernate.dialect">org.hibernate.dialect.MySQL5Dialect</prop>
                <prop key="hibernate.show_sql">true</prop>
            </props>
        </property>
    </bean>

    <bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
        <property name="entityManagerFactory" ref="entityManagerFactory" />
    </bean>

    <bean id="persistenceExceptionTranslationPostProcessor" class="org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor" />

    <tx:annotation-driven />

</beans>

The class where I attempt to use EntityManager

我尝试使用的课程 EntityManager

@Repository
public class ProductsService {

    @PersistenceContext
    EntityManager entityManager;

    @Transactional
    public GridResponse<Product> getProducts(GridRequest dRequest) {

        // The following line causes the exception: "java.lang.IllegalStateException: No transactional EntityManager available"
        Session session = entityManager.unwrap(Session.class);

        //...
    }

...

采纳答案by Andrei Stefan

For the @PersistenceContext EntityManager entityManager;approach, add tx:annotation-drivento your .xml configuration and mark your methods where you use entityManageras @Transactional.

对于该@PersistenceContext EntityManager entityManager;方法，添加tx:annotation-driven到您的 .xml 配置并将您使用的方法标记entityManager为@Transactional.

回答by B?ng Rikimaru

It can be use with @Autowired as shown in https://stackoverflow.com/a/33742769/2028440

它可以与 @Autowired 一起使用，如https://stackoverflow.com/a/33742769/2028440所示

@Autowired
private EntityManager entityManager;