Java 访问EntityManager时出现NullPointerException

我将Hibernate4、Spring3和JSF2用于一个小型应用程序，将Weblogic 10.3.6用作应用程序服务器

为了启用JPA2，我在commonv.cmd中添加了以下内容

@rem Enable JPA 2.0 functionality on WebLogic Server
set PRE_CLASSPATH=%BEA_HOME%\modules\javax.persistence_1.1.0.0_2-0.jar;
%BEA_HOME%\modules\com.oracle.jpa2support_1.0.0.0_2-1.jar

当我运行我的应用程序时，我在下面一行得到空指针异常。我如何解决这个问题

CriteriaBuilder cb = entityManager.getCriteriaBuilder();

我的刀

@Named
public class RequestDAOImpl implements RequestDAO {

protected EntityManager entityManager;

public void getRequest(RequestQueryData data){
        Map<String, String> filters = data.getFilters();
        int start = data.getStart();
        int end = data.getEnd();
        String sortField = data.getSortField();
        QuerySortOrder order = data.getOrder();

        CriteriaBuilder cb = entityManager.getCriteriaBuilder();
        CriteriaQuery<Request> c = cb.createQuery(Request.class);
        Root<Request> emp = c.from(Request.class);
        c.select(emp);
                ...... other code

@Named
公共类RequestDAOImpl实现RequestDAO{
受保护的实体管理器实体管理器；
public void getRequest（RequestQueryData数据）{
Map filters=data.getFilters（）；
int start=data.getStart（）；
int end=data.getEnd（）；
字符串sortField=data.getSortField（）；
QuerySortOrder=data.getOrder（）；
CriteriaBuilder cb=entityManager.getCriteriaBuilder（）；
CriteriaQuery c=cb.createQuery（Request.class）；
根emp=c.from（Request.class）；
c、 选择（emp）；
……其他代码

applicationContext.xml

<bean class="org.springframework.beans.factory.config.CustomScopeConfigurer">
        <property name="scopes">
            <map>
                <entry key="view">
                    <bean class="org.primefaces.spring.scope.ViewScope" />
                </entry>
            </map>
        </property>
    </bean>
    <context:component-scan base-package="net.test" />
    <!-- Data Source Declaration -->
    <bean id="DataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"
        destroy-method="close">
        <property name="driverClass" value="oracle.jdbc" />
        <property name="jdbcUrl"
            value="jdbc:oracle:thin:@server:1521:ORCL" />
        <property name="user" value="scott" />
        <property name="password" value="tiger" />
        <property name="maxPoolSize" value="10" />
        <property name="maxStatements" value="0" />
        <property name="minPoolSize" value="5" />
    </bean>     
    <!-- Session Factory Declaration -->
    <bean id="SessionFactory"
        class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
        <property name="dataSource" ref="DataSource" />
        <property name="annotatedClasses">
            <list>
                <value>net.test.model.Request</value>
            </list>
        </property>
        <property name="hibernateProperties">
            <props>
                <prop key="hibernate.dialect">org.hibernate.dialect.Oracle10gDialect</prop>
                <prop key="hibernate.show_sql">true</prop>
                <prop key="hibernate.query.factory_class">org.hibernate.hql.internal.classic.ClassicQueryTranslatorFactory
                </prop>
            </props>
        </property>
    </bean>
    <!-- Enable the configuration of transactional behavior based on annotations -->
    <tx:annotation-driven transaction-manager="txManager" />
    <!-- Transaction Manager is defined -->
    <bean id="txManager"
        class="org.springframework.orm.hibernate4.HibernateTransactionManager">
        <property name="sessionFactory" ref="SessionFactory" />
    </bean>

<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:tx="http://www.springframework.org/schema/tx"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/tx
http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd">
    <!-- Spring view scope customized -->

    <bean class="org.springframework.beans.factory.config.CustomScopeConfigurer">
        <property name="scopes">
            <map>
                <entry key="view">
                    <bean class="org.primefaces.spring.scope.ViewScope" />
                </entry>
            </map>
        </property>
    </bean>
    <context:component-scan base-package="net.test" />
    <!-- Data Source Declaration -->
    <bean id="DataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"
        destroy-method="close">
        <property name="driverClass" value="oracle.jdbc" />
        <property name="jdbcUrl"
            value="jdbc:oracle:thin:@server:1521:ORCL" />
        <property name="user" value="scott" />
        <property name="password" value="tiger" />
        <property name="maxPoolSize" value="10" />
        <property name="maxStatements" value="0" />
        <property name="minPoolSize" value="5" />
    </bean>
      <bean class="org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor"/>
    <!-- JPA Entity Manager Factory -->
    <bean id="entityManagerFactory" 
          class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"> 
         <property name="dataSource" ref="DataSource" />
         <property name="packagesToScan" value="net.test.model" />
         <property name="jpaVendorAdapter">
      <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">  
       </bean>
   </property>         
      </bean> 
      <bean id="defaultLobHandler" class="org.springframework.jdbc.support.lob.DefaultLobHandler" />        
    <!-- Session Factory Declaration -->
    <bean id="SessionFactory"
        class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
        <property name="dataSource" ref="DataSource" />
        <property name="annotatedClasses">
            <list>
                <value>net.test.model.Request</value>
            </list>
        </property>
        <property name="hibernateProperties">
            <props>
                <prop key="hibernate.dialect">org.hibernate.dialect.Oracle10gDialect</prop>
                <prop key="hibernate.show_sql">true</prop>
                <prop key="hibernate.query.factory_class">org.hibernate.hql.internal.classic.ClassicQueryTranslatorFactory
                </prop>
            </props>
        </property>
    </bean>
    <!-- Enable the configuration of transactional behavior based on annotations 
    <tx:annotation-driven transaction-manager="txManager" />-->
    <!-- Transaction Manager is defined 
    <bean id="txManager"
        class="org.springframework.orm.hibernate4.HibernateTransactionManager">
        <property name="sessionFactory" ref="SessionFactory" />
    </bean>-->

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

          <bean id="txManager"
        class="org.springframework.orm.hibernate4.HibernateTransactionManager">
        <property name="sessionFactory" ref="SessionFactory" />
    </bean>         

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

     <context:annotation-config/>


    <bean id="hibernateStatisticsMBean" class="org.hibernate.jmx.StatisticsService">
        <property name="statisticsEnabled" value="true" />
        <property name="sessionFactory" value="#{entityManagerFactory.sessionFactory}" />
    </bean>
    <bean name="ehCacheManagerMBean"
        class="org.springframework.cache.ehcache.EhCacheManagerFactoryBean" />

    <bean id="mbeanServer" class="org.springframework.jmx.support.MBeanServerFactoryBean">
        <property name="locateExistingServerIfPossible" value="true" />
    </bean>

    <bean id="jmxExporter" class="org.springframework.jmx.export.MBeanExporter" lazy-init="false">
        <property name="server" ref="mbeanServer" />
        <property name="registrationBehaviorName" value="REGISTRATION_REPLACE_EXISTING"/>
        <property name="beans">
            <map>               
                <entry key="SpringBeans:name=hibernateStatisticsMBean" value-ref="hibernateStatisticsMBean" />
                <entry key="SpringBeans:name=ehCacheManagerMBean" value-ref="ehCacheManagerMBean" />
            </map>
        </property>
    </bean>

</beans>

net.test.model.Request
org.hibernate.dialen.oracle10galent
真的
org.hibernate.hql.internal.classic.ClassicQueryTranslatorFactory

更新1

applicationContext.xml

<bean class="org.springframework.beans.factory.config.CustomScopeConfigurer">
        <property name="scopes">
            <map>
                <entry key="view">
                    <bean class="org.primefaces.spring.scope.ViewScope" />
                </entry>
            </map>
        </property>
    </bean>
    <context:component-scan base-package="net.test" />
    <!-- Data Source Declaration -->
    <bean id="DataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"
        destroy-method="close">
        <property name="driverClass" value="oracle.jdbc" />
        <property name="jdbcUrl"
            value="jdbc:oracle:thin:@server:1521:ORCL" />
        <property name="user" value="scott" />
        <property name="password" value="tiger" />
        <property name="maxPoolSize" value="10" />
        <property name="maxStatements" value="0" />
        <property name="minPoolSize" value="5" />
    </bean>     
    <!-- Session Factory Declaration -->
    <bean id="SessionFactory"
        class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
        <property name="dataSource" ref="DataSource" />
        <property name="annotatedClasses">
            <list>
                <value>net.test.model.Request</value>
            </list>
        </property>
        <property name="hibernateProperties">
            <props>
                <prop key="hibernate.dialect">org.hibernate.dialect.Oracle10gDialect</prop>
                <prop key="hibernate.show_sql">true</prop>
                <prop key="hibernate.query.factory_class">org.hibernate.hql.internal.classic.ClassicQueryTranslatorFactory
                </prop>
            </props>
        </property>
    </bean>
    <!-- Enable the configuration of transactional behavior based on annotations -->
    <tx:annotation-driven transaction-manager="txManager" />
    <!-- Transaction Manager is defined -->
    <bean id="txManager"
        class="org.springframework.orm.hibernate4.HibernateTransactionManager">
        <property name="sessionFactory" ref="SessionFactory" />
    </bean>

<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:tx="http://www.springframework.org/schema/tx"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/tx
http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd">
    <!-- Spring view scope customized -->

    <bean class="org.springframework.beans.factory.config.CustomScopeConfigurer">
        <property name="scopes">
            <map>
                <entry key="view">
                    <bean class="org.primefaces.spring.scope.ViewScope" />
                </entry>
            </map>
        </property>
    </bean>
    <context:component-scan base-package="net.test" />
    <!-- Data Source Declaration -->
    <bean id="DataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"
        destroy-method="close">
        <property name="driverClass" value="oracle.jdbc" />
        <property name="jdbcUrl"
            value="jdbc:oracle:thin:@server:1521:ORCL" />
        <property name="user" value="scott" />
        <property name="password" value="tiger" />
        <property name="maxPoolSize" value="10" />
        <property name="maxStatements" value="0" />
        <property name="minPoolSize" value="5" />
    </bean>
      <bean class="org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor"/>
    <!-- JPA Entity Manager Factory -->
    <bean id="entityManagerFactory" 
          class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"> 
         <property name="dataSource" ref="DataSource" />
         <property name="packagesToScan" value="net.test.model" />
         <property name="jpaVendorAdapter">
      <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">  
       </bean>
   </property>         
      </bean> 
      <bean id="defaultLobHandler" class="org.springframework.jdbc.support.lob.DefaultLobHandler" />        
    <!-- Session Factory Declaration -->
    <bean id="SessionFactory"
        class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
        <property name="dataSource" ref="DataSource" />
        <property name="annotatedClasses">
            <list>
                <value>net.test.model.Request</value>
            </list>
        </property>
        <property name="hibernateProperties">
            <props>
                <prop key="hibernate.dialect">org.hibernate.dialect.Oracle10gDialect</prop>
                <prop key="hibernate.show_sql">true</prop>
                <prop key="hibernate.query.factory_class">org.hibernate.hql.internal.classic.ClassicQueryTranslatorFactory
                </prop>
            </props>
        </property>
    </bean>
    <!-- Enable the configuration of transactional behavior based on annotations 
    <tx:annotation-driven transaction-manager="txManager" />-->
    <!-- Transaction Manager is defined 
    <bean id="txManager"
        class="org.springframework.orm.hibernate4.HibernateTransactionManager">
        <property name="sessionFactory" ref="SessionFactory" />
    </bean>-->

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

          <bean id="txManager"
        class="org.springframework.orm.hibernate4.HibernateTransactionManager">
        <property name="sessionFactory" ref="SessionFactory" />
    </bean>         

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

     <context:annotation-config/>


    <bean id="hibernateStatisticsMBean" class="org.hibernate.jmx.StatisticsService">
        <property name="statisticsEnabled" value="true" />
        <property name="sessionFactory" value="#{entityManagerFactory.sessionFactory}" />
    </bean>
    <bean name="ehCacheManagerMBean"
        class="org.springframework.cache.ehcache.EhCacheManagerFactoryBean" />

    <bean id="mbeanServer" class="org.springframework.jmx.support.MBeanServerFactoryBean">
        <property name="locateExistingServerIfPossible" value="true" />
    </bean>

    <bean id="jmxExporter" class="org.springframework.jmx.export.MBeanExporter" lazy-init="false">
        <property name="server" ref="mbeanServer" />
        <property name="registrationBehaviorName" value="REGISTRATION_REPLACE_EXISTING"/>
        <property name="beans">
            <map>               
                <entry key="SpringBeans:name=hibernateStatisticsMBean" value-ref="hibernateStatisticsMBean" />
                <entry key="SpringBeans:name=ehCacheManagerMBean" value-ref="ehCacheManagerMBean" />
            </map>
        </property>
    </bean>

</beans>

net.test.model.Request
org.hibernate.dialen.oracle10galent
真的
org.hibernate.hql.internal.classic.ClassicQueryTranslatorFactory

您的EntityManager似乎没有连接到DAO。请在XML中添加

@Autowired

、

@PersistenceContext

或一个ref。请注意，要仅使用

@Autowired

，必须将EntityManager指定为bean

另一种可能性是：如果您的DAO也没有被指定为bean（在XML中或使用各种

@Component

注释之一（可能是

@Repository

），Spring也不知道如何连接东西

更新： 这里有两种不同的解决方案。不过，在这些解决方案之前，请确保

    <mvc:annotation-driven />

及

在schemaLocation中

看起来您现在正在指定一个

EntityManager工厂

。这是一个好的开始。您现在也可以指定一个

EntityManager

<bean id="entityManager" class="org.springframework.orm.jpa.support.SharedEntityManagerBean">
    <property name="entityManagerFactory" ref="entityManagerFactory"/>
</bean>

或者，由于要在XML中指定一个数据源，您应该能够通过使用

@PersistenceContext

并向其传递一个ID值来引用它

@PersistenceContext(name="DataSource")
protected EntityManager entityManager;

---

我从来没有真正使用过后一种方法，但我见过它是这样做的。我通常在XML中指定

EntityManager

bean，并使用

@Autowired

，如前一种方法所述。

当我使用另一种方法

@Override public List getRequest（）时，我有一个问题{，

它在没有任何异常或错误的情况下工作。这是在访问EntityManager？它是否只在调用getCriteriaBuilder（）时抛出NPE？不，我根本没有访问EntityManager。我修改了我的applicationContext.xml，在我的问题中作为更新1包含。我仍然在

CriteriaBuilder cb=EntityManager.getCriteriaBuilder（）处收到空指针异常；

@Polppan-我已经更新了我的答案，现在问题似乎是注入依赖项的问题。小心——您的新XML似乎格式不正确。我看到一个

标记似乎没有开始标记。感谢您指出实体管理器的问题。我已经取得了一些进展，并设法解决了这个问题o在部署时消除所有异常。当前使用：-）

@PersistenceContext(name="DataSource")
protected EntityManager entityManager;