Eclipse Link编织的实体的Spring-data-jpa问题

Question

当我们使用EclipseLink为JPA实体使用静态编织时，我们的应用程序中就会出现异常。

该应用程序是一个web应用程序，使用SpringDataJPA和SpringDataRESTWebMVC提供CRUD功能来更改实体。

当实体类没有通过编织处理时，它就工作了。但一旦我们使用编织实体，我们就会得到：

org.springframework.http.converter.HttpMessageNotWritableException: Could not write JSON: 
 Conflicting getter definitions for property "rootParentDescriptor":   
  org.eclipse.persistence.descriptors.InheritancePolicy#isRootParentDescriptor(0 params) vs org.eclipse.persistence.descriptors.InheritancePolicy#getRootParentDescriptor(0 params) (through reference chain:    org.springframework.hateoas.Resources["content"]->java.util.UnmodifiableCollection[0]->org.eclipse.persistence.internal.descriptors.changetracking.AttributeChangeListener["descriptor"]->org.eclipse.persistence.descriptors.RelationalDescriptor["inheritancePolicy"]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: Conflicting getter definitions for property "rootParentDescriptor": org.eclipse.persistence.descriptors.InheritancePolicy#isRootParentDescriptor(0 params) vs org.eclipse.persistence.descriptors.InheritancePolicy#getRootParentDescriptor(0 params) (through reference chain: org.springframework.hateoas.Resources["content"]->java.util.UnmodifiableCollection[0]->org.eclipse.persistence.internal.descriptors.changetracking.AttributeChangeListener["descriptor"]->org.eclipse.persistence.descriptors.RelationalDescriptor["inheritancePolicy"])

..

Caused by: java.lang.IllegalArgumentException: Conflicting getter definitions for property "rootParentDescriptor": org.eclipse.persistence.descriptors.InheritancePolicy#isRootParentDescriptor(0 params) vs org.eclipse.persistence.descriptors.InheritancePolicy#getRootParentDescriptor(0 params)
at com.fasterxml.jackson.databind.introspect.POJOPropertyBuilder.getGetter(POJOPropertyBuilder.java:190) ~[jackson-databind-2.2.2.jar:2.2.2]

当JSON响应应包含一个实体时，就会发生这种情况。实体非常简单，只有两个属性，没有关联等。

以下是使用的版本：

<dependency>
 <groupId>org.springframework.data</groupId>
 <artifactId>spring-data-rest-webmvc</artifactId>
 <version>1.1.0.M1</version>
</dependency>

<dependency>
 <groupId>org.eclipse.persistence</groupId>
 <artifactId>org.eclipse.persistence.jpa</artifactId>
 <version>2.5.0</version>
</dependency>

<dependency>
    <groupId>org.springframework.data</groupId>
    <artifactId>spring-data-jpa</artifactId>
    <version>1.3.2.RELEASE</version>
</dependency>

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.2.2</version>
</dependency>

是否有支持这种组合的配置或描述这种问题的已知问题？

Answer 1

我将JPA@Transient注释属性视为Transient now，从而解决了这个问题。因此，只要您的持久性提供程序正确地使用了这些，您就可以了。如果不行，我们就得开罚单。

Spring数据JPA的1.3.5和1.4 RC1中将提供该修复程序。

Answer 2

经过一些研究，我找到了一个解决办法，但也许有人知道一个更好的解决办法。原因是，SpringDataCommons中的类JpaMetamodelMappingContext在编织过程中添加的实体类中找到了变量。它在元模型（JpaPersistentEntity）中收集它们作为属性，尽管这些字段只对EclipseLink的内部行为感兴趣。

我用自己的子类替换了JpaMetamodelMappingContext，这样就不会收集这些字段（比如@Transient）。这是用黑客手段完成的。

在spring配置中，我们向jpa:repositories添加了一个工厂类

<jpa:repositories base-package="de.viaboxx.vplan.database.dao"
                  entity-manager-factory-ref="entityManagerFactory"
                  factory-class="de.viaboxx.springframework.data.jpa.EclipseJpaRepositoryFactoryBean"/>

新的类Eclipse JpaRepositoryFactoryBean引入了JpaMetamodelMappingContext的新实现。这是源代码：（类从JpaRepositoryFactoryBean复制，在setEntityManager（）中进行了更改）

public class EclipseJpaRepositoryFactoryBean<T extends Repository<S, ID>, S, ID extends Serializable> extends
    TransactionalRepositoryFactoryBeanSupport<T, S, ID> {

private EntityManager entityManager;

/**
 * The {@link EntityManager} to be used.
 *
 * @param entityManager the entityManager to set
 */
@PersistenceContext
public void setEntityManager(EntityManager entityManager) {
    this.entityManager = entityManager;
    setMappingContext(
            new EclipseJpaMetamodelMappingContext(entityManager.getMetamodel())); // <<-- this is the only change
}

/*
 * (non-Javadoc)
 *
 * @see org.springframework.data.repository.support.
 * TransactionalRepositoryFactoryBeanSupport#doCreateRepositoryFactory()
 */
@Override
protected RepositoryFactorySupport doCreateRepositoryFactory() {
    return createRepositoryFactory(entityManager);
}

/**
 * Returns a {@link RepositoryFactorySupport}.
 *
 * @param entityManager
 * @return
 */
protected RepositoryFactorySupport createRepositoryFactory(EntityManager entityManager) {
    return new JpaRepositoryFactory(entityManager);
}

/*
 * (non-Javadoc)
 *
 * @see
 * org.springframework.beans.factory.InitializingBean#afterPropertiesSet()
 */
@Override
public void afterPropertiesSet() {

    Assert.notNull(entityManager, "EntityManager must not be null!");
    super.afterPropertiesSet();
}
}

过滤内部属性的Hack包含在类Eclipse JpaMetamodelMappingContext中（包必须是org.springframework.data.jpa.mapping才能访问类JpaPeristentEntityImpl！）

public class EclipseJpaMetamodelMappingContext extends JpaMetamodelMappingContext {
/**
 * Creates a new JPA {@link javax.persistence.metamodel.Metamodel} based {@link org.springframework.data.mapping.context.MappingContext}.
 *
 * @param model must not be {@literal null}.
 */
public EclipseJpaMetamodelMappingContext(Metamodel model) {
    super(model);
}

@Override
protected JpaPersistentProperty createPersistentProperty(Field field, PropertyDescriptor descriptor,
                                                         JpaPersistentEntityImpl<?> owner,
                                                         SimpleTypeHolder simpleTypeHolder) {
    // HACK: ignore fields added by eclipselink weaving
    // because they cause problems during JSON marshaling with spring-data-rest 1.1.0.M1
    if (field.getType().getName().startsWith("org.eclipse.") ||
            field.getType().equals(PropertyChangeListener.class)) {
        return new TransientPropertyToBeIgnored(field, descriptor, owner, simpleTypeHolder);
    } else {
        return super.createPersistentProperty(field, descriptor, owner, simpleTypeHolder);    // call super!
    }
}

static class TransientPropertyToBeIgnored extends AnnotationBasedPersistentProperty<JpaPersistentProperty>
        implements JpaPersistentProperty {

    @Override
    public boolean isTransient() {
        return true;  // this causes the property to be ignored!
    }

    public TransientPropertyToBeIgnored(Field field, PropertyDescriptor propertyDescriptor,
                                        PersistentEntity owner,
                                        SimpleTypeHolder simpleTypeHolder) {
        super(field, propertyDescriptor, owner, simpleTypeHolder);
    }

    @Override
    protected Association createAssociation() {
        return new Association<JpaPersistentProperty>(this, null);
    }
}
}

无论编织或未编织的实体如何，这都适用于我们。

使用Hibernate而不是EclipseLink时不会出现问题，但是使用Hibernate需要jackson Hibernate模块和其他配置更改。