EntityManager NullPointerException Spring + Hibernate + Maven

Question

Вот в чем дело ... У меня есть веб-проект Maven, основанный на spring3.0, и я хотел использовать hibernate + jpa для своего DA ... но когда я пытаюсь использовать объект entityManager, я просто получаю исключение nullPointerException. .. вот код:

@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;
}

когда я пытаюсь создать объект objet, я получаю сообщение об ошибке.

Это моё приложениеContext.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-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/tx  http://www.springframework.org/schema/tx/spring-tx-3.0.xsd">

<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>

И ошибка!

GRAVE: Servlet.service() for servlet [dispatchermaven] in context with path [/OneX-1] threw exception [Request processing failed; nested exception is java.lang.NullPointerException] with root cause
java.lang.NullPointerException
    at com.divux.onex.daoImp.DAOPersonImp.getAll(DAOPersonImp.java:45)
    at com.divux.onex.logic.FriendListLogic.getEntrys(FriendListLogic.java:23)
    at com.divux.onex.controller.FriendListController.getEntrys(FriendListController.java:25)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:616)
    at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:176)
    at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:426)
    at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:414)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:790)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:719)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:644)
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:560)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:393)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:240)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:164)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:462)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:563)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:399)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:317)
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:204)
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:182)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:311)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
    at java.lang.Thread.run(Thread.java:679)

Не знаю, сколько информации вам понадобится, но я дам вам, ребята, все, что вам нужно!

Большое спасибо! Извини за мой ужасный английский ...

Answer 1

PersistenceContex не внедряет entitymanager. Так что вы получаете NullPointerException, чтобы persistence.xml находился в правильном месте, а его имя устройства было правильным. Я также публикую пример конфигурации, чтобы вы могли соответствующим образом настроить applicationContex.

    <!-- 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>