我按照 here 发布的教程进行操作让基础应用程序与 Spring Data JPA 一起工作。现在，我如何理解，使用配置

<jpa:repositories base-package="my.package.to.scan" />

应该导致 Spring Data JPA 扫描该包以查找扩展 JpaRepository 的接口(interface)并为其创建一个 concreate bean，以便可以使用简单的 Spring @Autowired 在我的服务类中的任何位置使用它。但它失败了，说它找不到带有 className 的 bean(这是 bean 在创建时获得的默认名称，只需使用去大写的 ClassName)。

但是，当我像这样在 applicationContext 中手动配置 bean 时:

<bean id="ClassName" class="my.package.to.scan.ClassName"/>

Spring 能够找到 bean。然后我当然会得到一个错误，因为我想从一个接口(interface)创建一个 bean，这显然是行不通的。但关键是 Spring Data JPA“自动 bean 创建”似乎以某种方式失败了。

我附上了相关代码，你可以看看。顺便说一句，我应该提到我正在开发一个 portlet，所以不要想知道为什么我没有 spring-config。我目前只使用一个 applicationConfig 加上一个 MyPortlet-Portlet.xml 用于 portlet 配置(但这应该与这个问题无关)。我添加了 import 语句只是为了确保我没有使用错误的注解/类。

applicationContext.xml

<beans *** ALL MY XMLN's and XSI's *** />
<context:annotation-config />
<jpa:repositories base-package="model.repositories" />

// JPA specific configuration here: dataSource, persistenceUnitManager exceptionTranslator, entityManagerFactory, SessionFactory, transactionManager - should not be relevant for this problem, tell me if i'm wrong

<bean class="org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor" />

ICustomerService - 只是 CustomerService 的一个接口(interface)

import model.entities.Customer;
public interface ICustomerService {
        // example method
    public Customer getCustomer(Long customerId);   
}

CustomerService - 我的应用程序逻辑用来获取/设置 ORM 数据的类

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;
import org.springframework.stereotype.Repository;
import org.springframework.transaction.annotation.Transactional;
import model.entities.Customer;
import model.repositories.CustomerRepository;
import model.service.interfaces.ICustomerService;
@Repository
@Transactional(readOnly = true)
public class CustomerService implements ICustomerService{
    @Autowired
    private CustomerRepository repository;

    // example method
    @Override
    public Customer getCustomer(Long customerId){
        return repository.findById(customerId);
    }

CustomerRepository - Spring Data JPA 的存储库

import javax.annotation.Resource;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.transaction.annotation.Transactional;
import model.entities.Customer;
@Resource
@Transactional(readOnly = true)
public interface CustomerRepository extends JpaRepository<Customer, Long>{

    public Customer findById(Long id);
}

客户 - 我的示例实体

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name = "Customers")
public class Customer{

    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    @Column(name = "ID_CUSTOMER")
    private Long    id;

    @Column(name = "dbfirstname")
    private String  firstName;

    @Column(name = "dbname")
    private String  lastName;

    public Long getId(){
        return id;
    }

    public String getFirstName(){
        return firstName;
    }

    public void setFirstName(String firstName){
        this.firstName = firstName;
    }

    public String getLastName(){
        return lastName;
    }

    public void setLastName(String lastName){
        this.lastName = lastName;
    }
}

我刚从 WebSphere 的类路径 hell (该死，多么糟糕的产品)，现在我在这里。希望有人可以帮助我。

对究竟出了什么问题进行基本解释，也许可以更好地理解 Spring Autowiring 注入(inject)功能。我已经阅读了 spring 文档，但说实话:有很多方法可以配置某些东西，而我不太清楚选择其中一种配置样式时真正需要什么。

编辑

尝试更新项目后，我仍然收到错误消息。按照这里的要求提供更多细节(跟踪):

Exception created : org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'customerService': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private model.repositories.CustomerRepository model.service.CustomerService.repository; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'customerRepository': FactoryBean threw exception on object creation; nested exception is java.lang.NullPointerException
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:287)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1106)
    [...]
        at com.ibm.ws.http.HttpConnection.run(HttpConnection.java:522)
    at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:1563)
Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: private model.repositories.CustomerRepository model.service.CustomerService.repository; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'customerRepository': FactoryBean threw exception on object creation; nested exception is java.lang.NullPointerException
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:506)
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:87)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:284)
    ... 96 more
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'customerRepository': FactoryBean threw exception on object creation; nested exception is java.lang.NullPointerException
    at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.doGetObjectFromFactoryBean(FactoryBeanRegistrySupport.java:149)
    at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.getObjectFromFactoryBean(FactoryBeanRegistrySupport.java:102)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getObjectForBeanInstance(AbstractBeanFactory.java:1442)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:248)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:193)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.findAutowireCandidates(DefaultListableBeanFactory.java:848)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:790)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:707)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:478)
    ... 98 more
Caused by: java.lang.NullPointerException
    at org.hibernate.engine.transaction.internal.jta.JtaStatusHelper.getStatus(JtaStatusHelper.java:73)
    at org.hibernate.engine.transaction.internal.jta.JtaStatusHelper.isActive(JtaStatusHelper.java:115)
    at org.hibernate.engine.transaction.internal.jta.CMTTransaction.join(CMTTransaction.java:149)
    at org.hibernate.ejb.AbstractEntityManagerImpl.joinTransaction(AbstractEntityManagerImpl.java:1215)
    at org.hibernate.ejb.AbstractEntityManagerImpl.postInit(AbstractEntityManagerImpl.java:177)
    at org.hibernate.ejb.EntityManagerImpl.<init>(EntityManagerImpl.java:89)
    at org.hibernate.ejb.EntityManagerFactoryImpl.createEntityManager(EntityManagerFactoryImpl.java:179)
    at org.hibernate.ejb.EntityManagerFactoryImpl.createEntityManager(EntityManagerFactoryImpl.java:174)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:48)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:600)
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.invokeProxyMethod(AbstractEntityManagerFactoryBean.java:376)
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean$ManagedEntityManagerFactoryInvocationHandler.invoke(AbstractEntityManagerFactoryBean.java:517)
    at $Proxy325.createEntityManager(Unknown Source)

    at org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:234)
    at $Proxy328.createNamedQuery(Unknown Source)
    at org.springframework.data.jpa.repository.query.NamedQuery.<init>(NamedQuery.java:74)
    at org.springframework.data.jpa.repository.query.NamedQuery.lookupFrom(NamedQuery.java:96)
    at org.springframework.data.jpa.repository.query.JpaQueryLookupStrategy$DeclaredQueryLookupStrategy.resolveQuery(JpaQueryLookupStrategy.java:128)
    at org.springframework.data.jpa.repository.query.JpaQueryLookupStrategy$CreateIfNotFoundQueryLookupStrategy.resolveQuery(JpaQueryLookupStrategy.java:162)
    at org.springframework.data.jpa.repository.query.JpaQueryLookupStrategy$AbstractQueryLookupStrategy.resolveQuery(JpaQueryLookupStrategy.java:71)
    at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.<init>(RepositoryFactorySupport.java:303)
    at org.springframework.data.repository.core.support.RepositoryFactorySupport.getRepository(RepositoryFactorySupport.java:157)
    at org.springframework.data.repository.core.support.RepositoryFactoryBeanSupport.getObject(RepositoryFactoryBeanSupport.java:120)
    at org.springframework.data.repository.core.support.RepositoryFactoryBeanSupport.getObject(RepositoryFactoryBeanSupport.java:39)
    at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.doGetObjectFromFactoryBean(FactoryBeanRegistrySupport.java:142)

编辑 #2 按要求添加完整的 applicationContext.xml(包括我根据正在进行的讨论所做的更改)

<context:annotation-config />

<jpa:repositories base-package="model.repositories" />

<context:component-scan base-package="model,model.repositories,model.service,controller" />

<bean class="model.service.CustomerService"/>
<bean class="model.service.OrderService"/>
<bean class="model.repositories.CustomerRepository"/>
<bean class="model.repositories.OrderRepository"/>


<bean id="myExceptionTranslator" class="org.springframework.orm.hibernate4.HibernateExceptionTranslator" /> 

<jee:jndi-lookup id="dataSource" jndi-name="jdbc/mydata"
    resource-ref="true" cache="true" />


<bean id="pum"
    class="org.springframework.orm.jpa.persistenceunit.DefaultPersistenceUnitManager">
    <property name="persistenceXmlLocations">
        <list>
            <value>classpath*:META-INF/OverridePersistence.xml</value>
        </list>
    </property>
    <property name="defaultDataSource" ref="dataSource" />
</bean>


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

<bean id="mySessionFactory"
    class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
    <property name="dataSource" ref="dataSource" />
    <property name="packagesToScan" value="model"/>
    <property name="hibernateProperties">
        <value>hibernate.dialect=org.hibernate.dialect.MySQLDialect</value>
    </property>
</bean>

<bean id="transactionManager"
    class="org.springframework.orm.hibernate4.HibernateTransactionManager">
    <property name="entityManagerFactory" ref="entityManagerFactory"/>
    <property name="sessionFactory" ref="mySessionFactory" />
</bean>

<tx:annotation-driven />

<bean class="org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor" />

最佳答案

问题很可能出在您未显示的某些配置中。如果您发布了您遇到的错误，那也会很好。它可能与你想象的不一样。

我注意到关于您的配置的一件事是您使用的是 context:annotation-config 而不是 context:component-scan。后者将根据 @Component 系列注释自动检测和创建 bean。前者不这样做。

除此之外，您发布的所有内容看起来都应该可以正常工作，尽管有一些奇怪的事情，我稍后会谈到。我将您发布的所有代码复制到一个示例项目中并填写了一些详细信息，例如 maven pom , 一个 persistence.xml ，以及 the applicationContext.xml 的缺失部分.我还在服务中添加了一个“创建”方法，因此它实际上会做一些事情。有了这些到位和一个主要的类来驱动这一切，这是一个可运行的例子。您可以browse the code on github ，或者您可以克隆并运行它:

git clone git://github.com/zzantozz/testbed tmp
cd tmp/stackoverflow/10539417-basic-spring-data-jpa
mvn -q compile exec:java -Dexec.mainClass=rds.testbed.springDataJpa.SpringDataJp

现在是我注意到的奇怪之处。从上到下:

• 有了给定的代码，就不需要 PersistenceAnnotationBeanPostProcessor您已添加到 applicationContext.xml。它没有为你做任何事情。当然，很可能还有其他代码需要它而您没有展示。
• 您的 CustomerService 上的 @Repository 注释是 supposed to be used on DAO classes ，或与数据库交互的类。服务的适当注释是 @Service .
• ICustomerRepository 上的 @Resource 注释主要是 used for marking fields and methods for autowiring .我不确定是什么让你想把它放在你的存储库界面上，但它在那里没有做任何事情。
• 您的存储库不应是 @Transactional。这属于你的服务，你已经得到了它，所以没关系。请注意，它仍然可以与存储库上的 @Transactional 一起使用，因为它只是加入了由服务启动的现有事务。
• 再次值得注意的是，您没有使用 component scanning ，即使您有与 @Component 相关的注释(您的服务上的 @Repository)。这可能会给您带来一些问题。我没有打开组件扫描，而是在示例项目中使用 XML 手动创建了服务 bean。

所以...如果这还没有向你解释什么，如果你给我一个具体的错误，我可能会解释你为什么会得到它，并告诉你如何做才能使它正确。

关于java - Spring Data JPA - 注入(inject)失败 - BeanCreationException : Could not autowire field，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/10539417/