@Transactional 注释导致实体上的返回类型不兼容错误

Question

我有一个在 Spring MVC 中开发的 Restful Web 服务，它当前返回农民信息，并允许在数据库中删除和添加新农民。在扩展 Web 服务以包含农民顾问时，只要将事务注释添加到顾问 DAO 实现，我就会收到以下错误：

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'advisorDAO' defined in class path resource [applicationContext.xml]: Initialization of bean failed; nested exception is java.lang.IllegalArgumentException: methods with same signature getAdvisors() but incompatible return types: [interface java.util.List, class [Lorg.springframework.aop.Advisor;]

关于这个错误的奇怪之处在于，系统在将注释添加到类之前可以正常编译并且符合预期，但是由于我需要能够将实体持久保存到数据库中，因此需要事务。我知道错误的含义，但我不知道为什么这只是使用注释时的问题，甚至没有应用于编译器抱怨的方法。

Advisors DAO 界面：

public interface AdvisorDAO {
   public List<Advisor> getAdvisors();
   public Advisor getAdvisorByPk(int id);   
   public Advisor getAdvisorByFarmerID(int id);
   public Advisor getAdvisorByAdvisorID(int id);    
   public void saveAdvisor(Advisor advisor);
   public void deleteAdvisor(Advisor advisor);
   public void updateAdvisor (Advisor advisor);
}

接口实现：

public class JpaAdvisorDAO implements AdvisorDAO {

@PersistenceContext
private EntityManager entityManager;

public void setEntityManager(EntityManager entityManager) {
this.entityManager = entityManager;
}

@Override
public List<Advisor> getAdvisors() {
    return entityManager.createNamedQuery("Advisor.findAll").getResultList();
}

@Override
public Advisor getAdvisorByPk(int id) {
    Query query = entityManager.createNamedQuery("Advisor.findByPK");
    query.setParameter("advisorPk", id);
    return (Advisor) query.getSingleResult();
}   

@Override
public Advisor getAdvisorByFarmerID(int id) {
    Query query = entityManager.createNamedQuery("Advisor.findByFarmerId");
    query.setParameter("farmerId", id);
    return (Advisor) query.getSingleResult();
}

@Override
public Advisor getAdvisorByAdvisorID(int id) {
    Query query = entityManager.createNamedQuery("Advisor.findByAdvisorId");
    query.setParameter("advisorId", id);
    return (Advisor) query.getSingleResult();  
}    

@Override
@Transactional
public void saveAdvisor(Advisor advisor) {
    entityManager.persist(advisor);
}

@Override
@Transactional
public void deleteAdvisor(Advisor advisor) {
    entityManager.remove(entityManager.getReference(Advisor.class, advisor.getAdvisorPk()));

}

@Override
@Transactional
public void updateAdvisor (Advisor advisor) {
    entityManager.merge(advisor);
}

使用的上下文文件：

<?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:p="http://www.springframework.org/schema/p"
    xmlns:tx="http://www.springframework.org/schema/tx"
    xsi:schemaLocation="http://www.springframework.org/schema/beans 
      http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
      http://www.springframework.org/schema/aop 
      http://www.springframework.org/schema/aop/spring-aop-2.5.xsd
      http://www.springframework.org/schema/context 
      http://www.springframework.org/schema/context/spring-context.xsd
      http://www.springframework.org/schema/tx 
      http://www.springframework.org/schema/tx/spring-tx.xsd" xmlns:context="http://www.springframework.org/schema/context" xmlns:mvc="http://www.springframework.org/schema/mvc">


<bean id="farmerDAO" class="com.test.cmsservice.persistance.JpaFarmerDAO" />
<bean id="advisorDAO" class="com.test.cmsservice.persistance.JpaAdvisorDAO" />

<bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
    <property name="persistenceUnitName" value="SpringRestService"/>
    <property name="dataSource" ref="dataSource"/>
        <property name="jpaVendorAdapter">
            <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
                <property name="showSql" value="true"/>
                <property name="generateDdl" value="false"/>
                <property name="databasePlatform" value="org.hibernate.dialect.DerbyDialect"/>
            </bean>
        </property>
</bean> 
<context:annotation-config />
  <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
    <property name="driverClassName" value="org.apache.derby.jdbc.ClientDriver"/>
    <property name="url" value="jdbc:derby://localhost:1527/SpringDBTest"/>
    <property name="username" value="APP"/>
    <property name="password" value="app"/>
  </bean>
  <tx:annotation-driven />
  <bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
    <property name="entityManagerFactory" ref="entityManagerFactory"/>
    <property name="dataSource" ref="dataSource"/>
  </bean>
  <bean id="persistenceAnnotation" class="org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor" />

Answer 1

添加注解不能改变返回类型。

首先，您可能导入了错误的类型 - Advisor 也是一个弹簧类，因此请修正您的导入。

然后我怀疑你有一个旧版本的接口或其由类加载器加载的实现。异常消息表明其中一个方法返回List<Advisor>，另一个返回-Advisor[]。确保所有内容都已清理并保持最新状态。