java - Spring 4 + Hibernate 4 事务管理错误

Question

我对 Spring 的事务管理有点陌生。我认为我缺少一些配置，但我无法处理它。

错误是我遇到无法延迟初始化角色集合异常。

我正在为我的 DAO 使用 Spring Data。另外，我知道如何将 fetchType 设置为 Eager，但这正是我试图避免的。

DAO:

public interface CourseDao extends CrudRepository<CourseEntity, Long> {
    CourseEntity findByName(String name);
}

服务:

@Service
public class CourseMaterialSearchService {
    private final CourseDao courseDao;
    private final CourseMaterialEntityTransformer courseMaterialEntityTransformer;

    @Autowired
    public CourseMaterialSearchService(CourseDao courseDao, CourseMaterialEntityTransformer courseMaterialEntityTransformer) {
        super();
        this.courseDao = courseDao;
        this.courseMaterialEntityTransformer = courseMaterialEntityTransformer;
    }

    @Transactional
    public List<CourseMaterial> findMaterialsFor(final Long courseId) {
        final CourseEntity entity = courseDao.findOne(courseId);
        final List<CourseMaterialEntity> materials = entity.getCourseMaterialEntityList();
        return courseMaterialEntityTransformer.transformEntities(materials);
    }
}

我的 application-context.xml 是(当然这只是相关部分):

<bean id="entityManagerFactory"
    class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
    <property name="persistenceUnitName" value="example" />
    <property name="dataSource" ref="exampleDataSource" />
    <property name="packagesToScan" value="com.example.example.**.repository" />
    <property name="jpaVendorAdapter">
        <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
            <property name="showSql" value="true" />
            <property name="generateDdl" value="true" />
        </bean>
    </property>
</bean>
<tx:annotation-driven proxy-target-class="true" transaction-manager="transactionManager"/>

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

当我调用CourseMaterialSearchService中的findMaterialsFor方法时，发生异常。我该如何解决这个问题？

如有任何建议，我们将不胜感激。

谢谢大家。

堆栈跟踪:

org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.example.example.course.repository.domain.CourseEntity.courseMaterialEntityList, could not initialize proxy - no Session
org.hibernate.collection.internal.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:575)
org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:214)
org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:554)
org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:142)
org.hibernate.collection.internal.PersistentBag.iterator(PersistentBag.java:294)
com.example.example.course.service.transform.CourseMaterialEntityTransformer.transformEntities(CourseMaterialEntityTransformer.java:15)
com.example.example.course.service.CourseMaterialSearchService.findMaterialsFor(CourseMaterialSearchService.java:29)

类(class) Material 实体转换器:

public class CourseMaterialEntityTransformer {
        public List<CourseMaterial> transformEntities(final Iterable<CourseMaterialEntity> entities) {
            final List<CourseMaterial> result = new ArrayList<>();
            for (final CourseMaterialEntity entity : entities) {
                result.add(transformEntity(entity));
            }
            return result;
        }

    public CourseMaterial transformEntity(final CourseMaterialEntity entity) {
        final CourseMaterial result = new CourseMaterial();
        result.setId(entity.getId());
        result.setName(entity.getName());
        result.setCourseName(entity.getCourseEntity().getName());
        result.setCurrentFileName(entity.getCurrentFileName());
        result.setOriginalFileName(entity.getOriginalFileName());
        result.setCategory(entity.getMaterialCategoryEntity().getName());
        result.setUploader(entity.getUserEntity().getName());
        return result;
    }
}

com.example.example.course.service.transform.CourseMaterialEntityTransformer.transformEntities(CourseMaterialEntityTransformer.java:15):

for (final CourseMaterialEntity entity : entities) {

类(class)实体:

@Entity(name = "courses")
public class CourseEntity {
    @Id
    @GeneratedValue
    private Long id;

    private String name;

    @OneToMany(mappedBy = "courseEntity")
    private List<CourseMaterialEntity> courseMaterialEntityList;

    public Long getId() {
        return id;
    }

    public void setId(final Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(final String name) {
        this.name = name;
    }

    public List<CourseMaterialEntity> getCourseMaterialEntityList() {
        return courseMaterialEntityList;
    }

    public void setCourseMaterialEntityList(final List<CourseMaterialEntity> courseMaterialEntityList) {
        this.courseMaterialEntityList = courseMaterialEntityList;
    }

}

Answer 1

Spring 使用 AOP 来应用事务。 bean 上的 AOP 仅适用于同一应用程序上下文中的 bean。

您有一个<tx:annotation-driven />在你的application-context.xml ，由 ContextLoaderListener 加载。该文件包含<context:component-scan />它检测 @Service .

但是，如果您也有相同的 <context:component-scan />在 DispatcherServlet 加载的文件中，或者至少如果相同 @Service检测到它会导致该服务的另一个实例，该实例不会应用 AOP。

作为一般经验法则，您希望加载所有内容，但 @Controllers在你的ContextLoaderListener并且仅在 @Controllers 中与网络相关的内容(查看解析器， DispatcherServlet ) 。

参见context depended scan-component filter .