Hibernate EntityManager NullPointerException Spring+；冬眠+；专家

这就是。。。我有一个基于spring3.0的Maven web项目，我想将hibernate+jpa用于我的DA。。。但是当我尝试使用entityManager对象时，我得到了一个nullPointerException。。。代码如下：

@Repository
@Component
public class DAOPersonImp implements DAOPerson{

@PersistenceContext
private EntityManager entityManager;
@Override
public Person getById(int id) {
    // TODO Auto-generated method stub
    return entityManager.find(Person.class, id);
}

@Override
@Transactional
public List<Person> getAll() {
    Query query = entityManager.createQuery("SELECT * FROM  PERSON");
    List<Person> persons = null;
    persons = query.getResultList();
    return persons;
}

<bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
    <property name="dataSource" ref="dataSource" />
    <property name="persistenceUnitName" value="PersistUnit" />
    <property name="jpaVendorAdapter">
        <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
            <property name="database" value="MYSQL" />
            <property name="showSql" value="true" />
        </bean>
    </property>
</bean>

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

不知道你们需要多少信息，但我会给你们任何你们需要的

<bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
    <property name="dataSource" ref="dataSource" />
    <property name="persistenceUnitName" value="PersistUnit" />
    <property name="jpaVendorAdapter">
        <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
            <property name="database" value="MYSQL" />
            <property name="showSql" value="true" />
        </bean>
    </property>
</bean>

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

---

非常感谢！请原谅我糟糕的英语…

PersistenceContex没有注入entitymanager。因此您得到的是NullPointerException确保persistence.xml位于正确的位置，并且其单元名称正确。我还发布了一个配置示例，以便您可以相应地配置applicationContex

<bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
    <property name="dataSource" ref="dataSource" />
    <property name="persistenceUnitName" value="PersistUnit" />
    <property name="jpaVendorAdapter">
        <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
            <property name="database" value="MYSQL" />
            <property name="showSql" value="true" />
        </bean>
    </property>
</bean>

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

    <!-- Prints used SQL to stdout -->

    <property name="showSql" value="${hibernate.show.sql}"/>

    <!-- Generates tables. -->

    <property name="generateDdl" value="${hibernate.generate.ddl}"/>

    <property name="databasePlatform" value="${postgres.hibernate.database.platform}"/>

</bean>



<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"

      destroy-method="close">

    <property name="driverClass" value="${postgres.datasource.driver.class}"/>

    <property name="jdbcUrl" value="${postgres.datasource.jdbc.url}"/>

    <property name="user" value="${postgres.datasource.username}"/>

    <property name="password" value="${postgres.datasourse.password}"/>

    <property name="minPoolSize" value="1"/>

    <property name="acquireIncrement" value="1"/>

    <property name="maxPoolSize" value="3"/>

</bean>



<tx:annotation-driven transaction-manager="postgres.transactionManager"/>



<bean id="postgres.transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">

    <property name="entityManagerFactory" ref="entityManagerFactory"/>

    <property name="dataSource" ref="dataSource"/>

</bean>



<bean id="entityManagerFactory"

      class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">

    <property name="dataSource" ref="dataSource"/>

    <property name="jpaVendorAdapter" ref="jpaAdapter"/>

    <property name="persistenceUnitManager" ref="persistenceUnitManager"/>

    <property name="persistenceUnitName" value="PersistenceUnit"></property>

</bean>

<bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
    <property name="dataSource" ref="dataSource" />
    <property name="persistenceUnitName" value="PersistUnit" />
    <property name="jpaVendorAdapter">
        <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
            <property name="database" value="MYSQL" />
            <property name="showSql" value="true" />
        </bean>
    </property>
</bean>

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

你的applicationContext.xml中有吗？我不太熟悉Hibernate或Spring，但在使用JSF时，

@PersistenceContext

是用它的单元名编写的，比如

@PersistenceContext（unitName=“yournunitname”）

。我想这可能是个问题。如何调用dao.getAll（）？它看起来像是您直接创建的

DAOPersonImp

，但它应该是Spring的管理器（您不需要

@Component

）！在

FriendListLogic

（应标记为

@Component

）中，您应具有

@Autowired-DAOPerson

和在

FriendListController

（应标记为

@Controller

）中，您应具有

@Autowired FriendListLogic FriendListLogic

@dma_k我只是照你说的做了。。。错误也会改变！现在我在创建bean时遇到了问题（似乎是自动连线的问题）。。。对于错误输出的长度感到抱歉，但是。。。我不想错过任何线索。以下是org.springframework.beans.factory.BeanCreationException:创建名为“friendListLogic”的bean时出错：自动连线依赖项的注入失败；嵌套异常为org.springframework.beans.factory.BeanCreationException:无法自动关联字段：com.divux.onex.daoImp.DAOPersonImp com.divux.onex.logic.FriendListLogic.dao（没有足够的字符用于输出信息，是的，我似乎没有在正确的目录中获取persistence.xml…仍然有问题要找到它！但是你的贡献完全准确