Question

在我的域模型中，我有一个抽象的实体Indicator，由两个具体的Elementary和Composite继承抽象实体持有实体因子，以便两个子类可访问这种关系是双向的。因此，实体因子持有抽象实体指标的实例当然，实例是Elementary或Composite。

@Entity  
@Inheritance(strategy = JOINED)  
public abstract class Indicator implements Serializable {  
    @OneToMany(mappedBy = "indicator")  
    private List<Factor> factors = new ArrayList<Factor>();  
    ...  
}

@Entity
@Audited
public class Factor implements Serializable {
    @ManyToOne(optional = false)
    @JoinColumn(name = "ID_RSK_IND", nullable = false)
    @ForeignKey(name = "FK_FAC__IND")
    private Indicator indicator;
}

@Entity
@Audited
public class Elementary extends Indicator {
    ...
}

@Entity
@Audited
public class Composite extends Indicator {
    ...
}

我使用Dozer将这些实体映射到自己，以“破坏”hibernate工具并将其推送到客户端（GWT）。

Whith“经典”Hibernate，一切正常：Dozer越过豆子模型复制它。

但是，当我使用Envers AuditReader查询版本化实体时，我得到一个InstantiationException。它来自于Factor的实例尝试实例化Indicator的实例

09:36:04,702 - ERROR - org.dozer.MappingProcessor - Field mapping error -->
  MapId: null
  Type: null
  Source parent class: com.sg.rrf.l2r.shared.entity.market.indicator.elementary.Elementary
  Source field name: factors
  Source field type: class org.hibernate.envers.internal.entities.mapper.relation.lazy.proxy.ListProxy
  Source field value: [1]
  Dest parent class: com.sg.rrf.l2r.shared.entity.market.indicator.elementary.Elementary
  Dest field name: factors
  Dest field type: java.util.List
org.dozer.MappingException: java.lang.InstantiationException
    at org.dozer.util.MappingUtils.throwMappingException(MappingUtils.java:82)
    at org.dozer.factory.ConstructionStrategies$ByConstructor.newInstance(ConstructionStrategies.java:280)
    at org.dozer.factory.ConstructionStrategies$ByConstructor.create(ConstructionStrategies.java:245)
    at org.dozer.factory.DestBeanCreator.create(DestBeanCreator.java:65)
    at org.dozer.MappingProcessor.mapCustomObject(MappingProcessor.java:489)
    at org.dozer.MappingProcessor.mapOrRecurseObject(MappingProcessor.java:446)
    at org.dozer.MappingProcessor.mapFromFieldMap(MappingProcessor.java:342)
    at org.dozer.MappingProcessor.mapField(MappingProcessor.java:288)
    at org.dozer.MappingProcessor.map(MappingProcessor.java:248)
    at org.dozer.MappingProcessor.map(MappingProcessor.java:197)
    at org.dozer.MappingProcessor.mapCustomObject(MappingProcessor.java:495)
    at org.dozer.MappingProcessor.mapOrRecurseObject(MappingProcessor.java:446)
    at org.dozer.MappingProcessor.addOrUpdateToList(MappingProcessor.java:776)
    at org.dozer.MappingProcessor.addOrUpdateToList(MappingProcessor.java:850)
    at org.dozer.MappingProcessor.mapListToList(MappingProcessor.java:686)
    at org.dozer.MappingProcessor.mapCollection(MappingProcessor.java:541)
    at org.dozer.MappingProcessor.mapOrRecurseObject(MappingProcessor.java:434)
    at org.dozer.MappingProcessor.mapFromFieldMap(MappingProcessor.java:342)
    at org.dozer.MappingProcessor.mapField(MappingProcessor.java:288)
    at org.dozer.MappingProcessor.map(MappingProcessor.java:248)
    at org.dozer.MappingProcessor.map(MappingProcessor.java:197)
    at org.dozer.MappingProcessor.map(MappingProcessor.java:187)
    at org.dozer.MappingProcessor.map(MappingProcessor.java:124)
    at org.dozer.MappingProcessor.map(MappingProcessor.java:119)
    at org.dozer.DozerBeanMapper.map(DozerBeanMapper.java:120)
    at com.sg.rrf.l2r.server.audit.AuditTransactionalBean.getEntityForRevision(AuditTransactionalBean.java:30)
    at com.sg.rrf.l2r.server.audit.AuditTransactionalBean$$FastClassByCGLIB$$78958945.invoke(<generated>)
    at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:713)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
    at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:98)
    at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:262)
    at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:95)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.aop.framework.adapter.MethodBeforeAdviceInterceptor.invoke(MethodBeforeAdviceInterceptor.java:52)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.aop.framework.adapter.AfterReturningAdviceInterceptor.invoke(AfterReturningAdviceInterceptor.java:52)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.aop.aspectj.AspectJAfterThrowingAdvice.invoke(AspectJAfterThrowingAdvice.java:58)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:646)
    at com.sg.rrf.l2r.server.audit.AuditTransactionalBean$$EnhancerByCGLIB$$36312869.getEntityForRevision(<generated>)
    at com.sg.rrf.l2r.server.audit.AuditServiceImpl.getEntityForRevision(AuditServiceImpl.java:37)
    at com.sg.rrf.l2r.server.market.indicator.audit.IndicatorAuditServiceImplTest.assertElementaryValues(IndicatorAuditServiceImplTest.java:120)
    at com.sg.rrf.l2r.server.market.indicator.audit.IndicatorAuditServiceImplTest.testAuditElementary(IndicatorAuditServiceImplTest.java:105)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
    at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:74)
    at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:83)
    at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:72)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:232)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:89)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)
    at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
    at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:71)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:236)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:175)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
Caused by: java.lang.InstantiationException
    at sun.reflect.InstantiationExceptionConstructorAccessorImpl.newInstance(InstantiationExceptionConstructorAccessorImpl.java:30)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
    at org.dozer.factory.ConstructionStrategies$ByConstructor.newInstance(ConstructionStrategies.java:276)
    ... 74 more

它是否来自Envers使用延迟加载的事实，即使指定了Eager？

PS：当然，我需要从指标到因子的双向导航。

Answer 1

尝试将字段factors映射到Elementary类型的新对象的字段factors，但此处的属性是List接口，其中没有具体类型。

此字段的映射适用于实际的域模型类型，但不适用于hibernate代理。

您是否使用ArrayList初始化factors？看起来如此，否则非Envers映射将无效。

这可能与dozer在映射泛型类型（例如列表）时遇到的一些限制有关，因为通用信息在运行时不可用，因此dozer不知道列表包含的对象的类型，所以它试图从源集合的内容推断它。

根据Dozer documentation：

如果没有为目标字段指定提示，那么目标集合将填充对象与src Collection中的元素类型相同。

所以要解决这个问题有几种方法：

1 - 在此属性的映射上放置一个推土机提示以指定目标类型，这样就不会尝试推断它：

<field>
  <a>factors</a> 
  <b>factors</b> 
  <b-hint>your.target.class.Here</b-hint> 
</field>

2 - 编写并向此属性应用Dozer custom converter，您可以手动映射此列表，这将始终有效（使用基于泛型的自定义转换器API）。

3 - 通过以另一种方式在序列化时解决LazyInitialization，完全避免需要映射和Dozer：通过使用Open Session In View确保hibernate会话一直保持打开状态直到序列化请求如果在Spring应用程序中，或者类似的话，否则。

其中一种方法应该解决它，如果仍然怀疑你总是可以：

发布推土机映射和factors类型的代码？
使用调试器，您可以在ConstructionStrategies第280行中放置一个断点，以查看它尝试实例化的抽象类或接口是什么。

Answer 2

这是我的推土机映射：

protected final static DozerBeanMapper MAPPER = new DozerBeanMapper();
static {
    BeanMappingBuilder builder = new BeanMappingBuilder() {
        @Override
        protected void configure() {
            mapping(Elementary.class, Elementary.class);
            mapping(Composite.class, Composite.class);
        }
    };

    MAPPER.addMapping(builder);
}

由于这种映射，Dozer可以映射Hibernate代理的bean 但是通过这种映射，Dozer无法映射Envers代理bean。

我不认为这个问题是由于Collection映射造成的。当我在Instanciation上放置一个breakPoint时，我在org.dozer.factory.ConstructionStrategies.newInstance（Class clazz）方法中。 clazz参数是Indicator.class 此外，假设我不使用Dozer，我在DAO中调用此代码：

Indicator indicator = elementary.getFactors().get(0).getIndicator();
System.out.println(indicator.getClass().getSimpleName());

打印“Indicator _ $$ _ javassist_6”。

测试

indicator instanceof Elementary

或

indicator instanceof Composite

返回false。

使用经典Hibernate（没有Envers）的相同测试对其中一个返回true并打印正确的类名（即使在ManyToOne指示器属性上使用FetchType.LAZY！）

Hibernate Envers：多态性问题

2 个答案: