Spring 数据 JPA。 Repositories 继承，抛出 BeanCreationException，NullPointerException

Question

所以我开始使用 Spring Data JPA，一开始我发现它非常容易使用，尤其是对于简单的 POJO 实体，我设法对单个实体(人)执行简单的 CRUD 操作，但随着我深入研究我的设计(继承)，当涉及到继承设计时，我开始很难处理 Spring JPA 存储库。

图例:

POJO

存储库

使用上述两个的示例类

抛出异常

xml配置

Person 类(基类、抽象类)

 @MappedSuperclass
 public abstract class Person {
       ..properties, getters and setters with hibernate annotations
}

学生类(子类，扩展 Person)

 @Entity
 @Table(name = "STUDENT")
 public class Student extends Person {
        .. properties, getters and setters SPECIFIC for a student
 }

存储库

PersonRepository(基础、父存储库)

 public interface PersonRepository<T extends Person, ID extends Serializable> extends JpaRepository<T, ID> {
 }    

StudentRepository(子级，扩展 PersonRepository)

 public interface StudentRepository extends PersonRepository<Student, Integer>{
 }

示例类

 @Service ("manager")
  public class Manager {

  @SuppressWarnings("rawtypes")
  @Resource (name = "personRepository")
  private PersonRepository personRepository;

  @SuppressWarnings("unchecked")
  public void savePerson(Person p) {

      personRepository.save(p);
  }
}

抛出异常

Exception in thread "main" org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'manager': Injection of resource dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'personRepository': FactoryBean threw exception on object creation; nested exception is java.lang.NullPointerException at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.postProcessPropertyValues(CommonAnnotationBeanPostProcessor.java:308) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1185) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:537) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:475) at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:302) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:228) at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:298) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:193) at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:703) at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:760) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:482) at org.springframework.context.support.ClassPathXmlApplicationContext.(ClassPathXmlApplicationContext.java:139) at org.springframework.context.support.ClassPathXmlApplicationContext.(ClassPathXmlApplicationContext.java:83) at edu.main.Main.main(Main.java:12) Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'personRepository': FactoryBean threw exception on object creation; nested exception is java.lang.NullPointerException at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.doGetObjectFromFactoryBean(FactoryBeanRegistrySupport.java:175) at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.getObjectFromFactoryBean(FactoryBeanRegistrySupport.java:103) at org.springframework.beans.factory.support.AbstractBeanFactory.getObjectForBeanInstance(AbstractBeanFactory.java:1512) at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:313) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:198) at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.autowireResource(CommonAnnotationBeanPostProcessor.java:446) at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.getResource(CommonAnnotationBeanPostProcessor.java:420) at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor$ResourceElement.getResourceToInject(CommonAnnotationBeanPostProcessor.java:545) at org.springframework.beans.factory.annotation.InjectionMetadata$InjectedElement.inject(InjectionMetadata.java:155) at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:87) at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.postProcessPropertyValues(CommonAnnotationBeanPostProcessor.java:305) ... 13 more Caused by: java.lang.NullPointerException at java.lang.Class.isAssignableFrom(Native Method) at org.springframework.data.jpa.repository.support.JpaEntityInformationSupport.getMetadata(JpaEntityInformationSupport.java:58) at org.springframework.data.jpa.repository.support.JpaRepositoryFactory.getEntityInformation(JpaRepositoryFactory.java:145) at org.springframework.data.jpa.repository.support.JpaRepositoryFactory.getTargetRepository(JpaRepositoryFactory.java:83) at org.springframework.data.jpa.repository.support.JpaRepositoryFactory.getTargetRepository(JpaRepositoryFactory.java:66) at org.springframework.data.repository.core.support.RepositoryFactorySupport.getRepository(RepositoryFactorySupport.java:146) 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:168)

xml配置

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:repository="http://www.springframework.org/schema/data/repository"
xmlns:jpa="http://www.springframework.org/schema/data/jpa"         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-4.0.xsd
     http://www.springframework.org/schema/context  
     http://www.springframework.org/schema/context/spring-context-4.0.xsd
     http://www.springframework.org/schema/tx 
     http://www.springframework.org/schema/tx/spring-tx-4.0.xsd
     http://www.springframework.org/schema/data/repository
     http://www.springframework.org/schema/data/repository/spring-repository.xsd
     http://www.springframework.org/schema/data/jpa 
     http://www.springframework.org/schema/data/jpa/spring-jpa.xsd">


<context:annotation-config />
<context:component-scan base-package="edu.service" />
<jpa:repositories base-package="edu.repository" />
<tx:annotation-driven />

<context:property-placeholder
    location="classpath:properties/database.properties"
    ignore-unresolvable="false" />

<bean id="dataSource"
    class="org.springframework.jdbc.datasource.DriverManagerDataSource">
    <property name="driverClassName" value="${jdbc.driverClassName}" />
    <property name="url" value="${jdbc.url}" />
    <property name="username" value="${jdbc.username}" />
    <property name="password" value="${jdbc.password}" />
</bean>

<bean id="entityManagerFactory"
    class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
    <property name="dataSource" ref="dataSource" />
    <property name="packagesToScan">
        <list>
            <value>edu.domain</value>
        </list>
    </property>
    <property name="persistenceUnitName" value="personPU"/>
    <property name="jpaVendorAdapter">
        <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter" />
    </property>
    <property name="jpaProperties">
        <props>
            <prop key="hibernate.dialect">org.hibernate.dialect.MySQLDialect</prop>
            <prop key="hibernate.show_sql">false</prop>
        </props>
    </property>
</bean>

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

我试图找到一个特定的词来搜索类似的问题，但没有运气，导致我的存储库没有存储库 bean(NullPointerException/BeanCreationException)的问题可能是什么？还有一件事我想补充一点，我的设计模式是不是做错了什么？我应该将我的 POJO 继承模式反射(reflect)到我的存储库中吗？我试图让我的 PersonRepository 对我的 POJO/Entites 执行操作，这些 POJO/Entites 是 Person 类(抽象父类)的子类，这就是为什么我想出了存储库继承的想法。我的具体目标是，在使用 PersonRepository 扩展 Person 的任何对象上持久化/执行 CRUD。非常感谢任何帮助/建议/评论。请。非常感谢

Answer 1

我认为 PersonRepository 应该用 @NoRepositoryBean 注释。

在我的应用程序中，我是这样做的:

家长:

@NoRepositoryBean
public interface UserRepository<T> extends JpaRepository<T, Long> {
}

child :

@Repository
public interface EmployeeRepository extends UserRepository<Employee> {
}

希望对您有所帮助。