的EntityManager是空與XMLless JPA 2.1

Question

我從休眠遷移到JPA 2.1，我跟着這個tutorial，創建沒有的persistence.xml

一個JPA的配置，但EntityManager的是空當Tomcat啓動。

我的所有實體都使用@Entity註解。

這裏是我的applicationContext.xml：

<context:component-scan 
     base-package="br.com.foo, br.com.bar"/> 

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

<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager"> 
    <property name="entityManagerFactory" ref="entityManagerFactoryBean" /> 
</bean> 
<tx:annotation-driven/> 

<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource"> 
    <property name="driverClassName" value="com.mysql.jdbc.Driver" /> 
    <property name="url" value="jdbc:mysql://localhost:3306/myDb" /> 
    <property name="username" value="root" /> 
    <property name="password" value="root" /> 
</bean> 

<bean id="entityManagerFactoryBean" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"> 
    <property name="dataSource" ref="dataSource" /> 
    <property name="packagesToScan" value="br.com.foo.persistence" /> 
    <property name="jpaVendorAdapter"> 
    <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter" /> 
    </property> 
<property name="jpaProperties"> 
    <props> 
     <prop key="hibernate.dialect">org.hibernate.dialect.MySQL5Dialect</prop> 
    </props> 
    </property> 
</bean> 
... 

GenericDAO，從它的所有其他DAO繼承：

package br.com.bar; 

@Repository 
@Transactional 
public abstract class GenericDAOImpl<Entity> implements GenericDAO<Entity> { 

@PersistenceContext 
private EntityManager manager; 

protected SessionFactory sessionFactory; 

public GenericDAOImpl() { 
    this.sessionFactory = manager.unwrap(SessionFactory.class); //this line throws NullPointerException 
} 
... 

的實體：

package br.com.foo.persistence; 

@Entity 
@Table(name = "USER") 
@Inheritance(strategy = InheritanceType.JOINED) 
public class User extends BaseEntity { 

private static final long serialVersionUID = 3966629079539419005L; 

    @Column(name = "NAME", length = 200) 
    private String name; 

pom.xml中

<dependency> 
     <groupId>org.hibernate</groupId> 
     <artifactId>hibernate-entitymanager</artifactId> 
     <version>${hibernate.version}</version> 
     <type>jar</type> 
     <scope>compile</scope> 
    </dependency> 
    <dependency> 
     <groupId>org.hibernate.javax.persistence</groupId> 
     <artifactId>hibernate-jpa-2.1-api</artifactId> 
     <version>1.0.0.Final</version> 
    </dependency> 
    <dependency> 
     <groupId>org.hibernate</groupId> 
     <artifactId>hibernate-core</artifactId> 
     <version>${hibernate.version}</version> 
     <type>jar</type> 
     <scope>compile</scope> 
    </dependency> 
    <dependency> 
     <groupId>org.hibernate</groupId> 
     <artifactId>hibernate-validator</artifactId> 
     <version>4.2.0.Final</version> 
    </dependency> 
    <dependency> 
     <groupId>org.hibernate.common</groupId> 
     <artifactId>hibernate-commons-annotations</artifactId> 
     <version>4.0.1.Final</version> 
     <classifier>tests</classifier> 
    </dependency> 
    <dependency> 
     <groupId>org.hibernate</groupId> 
     <artifactId>hibernate-c3p0</artifactId> 
     <version>3.3.1.GA</version> 
    </dependency> 

錯誤的堆棧跟蹤：

GRAVE: Exception sending context initialized event to listener instance of class org.springframework.web.context.ContextLoaderListener 
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'companyDAOImpl' defined in file [C:\Users\marcelo\workspace\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\wtpwebapps\evcash-core\WEB-INF\classes\br\com\foo\CompanyDAOImpl.class]: Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [br.com.foo.dao.CompanyDAOImpl]: Constructor threw exception; nested exception is java.lang.NullPointerException 
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1110) 
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1055) 
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:510) 
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:482) 
at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306) 
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) 
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302) 
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197) 
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:751) 
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:861) 
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:541) 
at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:444) 
at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:326) 
at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:107) 
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4939) 
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5434) 
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) 
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1559) 
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1549) 
at java.util.concurrent.FutureTask.run(FutureTask.java:262) 
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) 
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) 
at java.lang.Thread.run(Thread.java:745) 
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [br.com.bar.dao.CompanyDAOImpl]: Constructor threw exception; nested exception is java.lang.NullPointerException 
at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:154) 
at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:89) 
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1103) 
... 22 more 
Caused by: java.lang.NullPointerException 
at br.com.bar.dao.impl.GenericDAOImpl.<init>(GenericDAOImpl.java:39) 
at br.com.foo.dao.CompanyDAOImpl.<init>(CompanyDAOImpl.java:19) 
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) 
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57) 
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) 
at java.lang.reflect.Constructor.newInstance(Constructor.java:526) 
at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:142) 
... 24 more 

CompanyDAOImpl：

package br.com.foo.dao; 

@Repository 
public class CompanyDAOImpl 
    extends GenericDAOImpl<Company> 
    implements CompanyDAO{ 

@Override 
protected Class<Company> getClazz() { 
    return Company.class; 
} 
... 

Answer 1

的EntityManager manager的實例未在構造函數中定義。 Spring injects the dependencies after the object is instantiated。