Question

我正在使用JPA和spring将我的JBOss服务器连接到oracle数据库。

以下是我的配置：

database.xml

<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx"
    xmlns:util="http://www.springframework.org/schema/util" xmlns:task="http://www.springframework.org/schema/task"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans     
        http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
        http://www.springframework.org/schema/context 
        http://www.springframework.org/schema/context/spring-context-3.0.xsd
        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd
        http://www.springframework.org/schema/aop
        http://www.springframework.org/schema/aop/spring-aop-3.0.xsd
        http://www.springframework.org/schema/task 
        http://www.springframework.org/schema/task/spring-task.xsd
        http://www.springframework.org/schema/tx
        http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
        http://www.springframework.org/schema/util
        http://www.springframework.org/schema/util/spring-util-3.0.xsd">

    <context:annotation-config />

    <context:component-scan base-package="com.example" />

    <!-- Add JPA support -->
    <bean id="emf"
        class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
        <property name="persistenceUnitName" value="unitDS" />
        <property name="persistenceXmlLocation" value="classpath:META-INF/persistence.xml" />
        <property name="loadTimeWeaver">
            <bean
                class="org.springframework.instrument.classloading.InstrumentationLoadTimeWeaver" />
        </property>
    </bean>

    <!-- Add Transaction support -->
    <bean id="mtsTxManager" class="org.springframework.orm.jpa.JpaTransactionManager">
        <property name="entityManagerFactory" ref="emf" />
    </bean>

    <!-- Use @Transaction annotations for managing transactions -->
    <tx:annotation-driven transaction-manager="mtsTxManager"
        proxy-target-class="true" />

</beans>

的persistence.xml

<?xml version="1.0" encoding="UTF-8"?>
<!-- @version $Date: 2010-06-04 15:50:29 +0200 (Fri, 04 Jun 2010) $ | $LastChangedBy: 
    ext_computaris_eprager $ | LastChangedRevision: $Rev: 2424 $ -->
<persistence version="2.0"
    xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">

    <persistence-unit name="unitDS"
        transaction-type="RESOURCE_LOCAL">

        <provider>org.hibernate.ejb.HibernatePersistence</provider>
        <non-jta-data-source>java:jboss/datasources/unitDS</non-jta-data-source>


        <class>com.example.foo</class>
        <class>com.example.bar</class>



        <!-- properties specific for the underlying implementation of the JPA EntityManager 
            (Hibernate) -->
        <properties>
            <!-- ////////////// HBM/DDL related properties ////////////// were removed 
                from here (set as system properties in tests) -->
            <!-- NCA -->
            <property name="hibernate.hbm2ddl.auto" value="update" />
            <property name="jboss.entity.manager.factory.jndi.name"
                value="java:/locationserverEntityManagerFactory" />

            <!-- ////////////// Enable JTA transaction ////////////// -->
            <property name="transaction.factory_class"
                value="org.hibernate.transaction.JTATransactionFactory" />
            <property name="jta.UserTransaction" value="java:comp/UserTransaction" />
            <property name="hibernate.transaction.manager_lookup_class"
                value="org.hibernate.transaction.JBossTransactionManagerLookup" />
            <!-- ////////////// debugging/testing related properties ////////////// -->
            <property name="hibernate.show_sql" value="false" />
            <property name="hibernate.format_sql" value="false" />
            <property name="hibernate.use_sql_comments" value="false" />

            <!-- 2nd level cache -->
<!--            <property name="hibernate.cache.provider_class" -->
<!--                value="net.sf.ehcache.hibernate.SingletonEhCacheProvider" /> -->
<!--            <property name="net.sf.ehcache.configurationResourceName" -->
<!--                value="/ehcache.xml" /> -->
<!--            <property name="hibernate.cache.use_query_cache" value="true" /> -->
<!--            <property name="hibernate.cache.use_second_level_cache" -->
<!--                value="true" /> -->
<!--            <property name="hibernate.generate_statistics" value="true" /> -->
        </properties>
    </persistence-unit>

</persistence>

弹簧上下文正常初始化。我收到了消息：

Starting persistence unit unitDS

当我启动服务器时。

我还有一个抽象的dao JPA，我使用注释@persistenceContext注入我的上下文：

public class AbstractDaoJpa<E, PK> implements DaoBase<E, PK> {

    /**
     * 
     */
    @PersistenceContext(unitName="unitDS")
    @Qualifier(value = "entityManagerFactory")
    private EntityManager em;

问题是当我尝试连接到我的数据库时，我的EntityManager始终为空。

我不明白这个问题来自哪里。我配置不好吗？

我尝试了几个类似帖子的解决方案，但无法解决我的问题。

Answer 1

我不确定，如果这是问题所在，但在Spring配置中，您有emf作为bean名称，而在AbstractDao中，您有entityManagerFactory作为限定符。所以我猜Spring没有注入正确的bean。

Answer 2

您似乎没有添加<context:component-scan base-package="your.package" />来启用组件扫描。为什么不尝试使用适当的包

Answer 3

我知道情况已经很晚了，但我会写信以备将来参考。使用 new 关键字创建实施实例时会有一个问题。有关详细信息，请查看this thread

Answer 4

它可能有某些因素 *缺少persistence.xml持久性提供程序

使用任何配置设置applicationContext.xml后，您将获得entitymanagerfactory，即来自LocalEntity，LocalContainer或JNDI Lookup。

使用persistenceContext
```
  private EntityManager em;
```

用@transactional，@ Repository

分配的类

但是你仍然得到em = null，这背后的原因是你没有使用依赖注入来调用你的类。

即使启动了持久性单元实体，JPA Spring注入EntityManager也为null

4 个答案: