Java &引用；组合中不兼容的数据类型“；导致；无法初始化集合"；在JPA中，具有继承的双向关系

我试图在Hibernate，JPA中实现以下图表

我试图以这种方式实现它

为了农场

@Entity
public class Farm implements Serializable{

    @OneToMany(mappedBy = "farm", cascade = { CascadeType.ALL }, targetEntity=AbstractAnimals.class, fetch=FetchType.LAZY)
    private List<AbstractAnimal> animals = new ArrayList<AbstractAnimals>();

}

对于抽象的哺乳动物

@MappedSuperClass
public abstract class AbstractMammalian extends AbstractAnimal implements Serializable{
    ... other attributes and getter and setter
}

为了所有的周年纪念

@Entity
public abstract class 'Animal' extends 'supertype' implements Serializable{

    ... other attributes and getter and setter
}

当我尝试获取所有农场动物时，我得到了以下错误

org.hibernate.exception.SQLGrammarException: could not initialize a collection: [my.example.Farm.animals#24]
    at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:92)
    at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
    at org.hibernate.loader.Loader.loadCollection(Loader.java:2173)
    at org.hibernate.loader.collection.CollectionLoader.initialize(CollectionLoader.java:62)
    at org.hibernate.persister.collection.AbstractCollectionPersister.initialize(AbstractCollectionPersister.java:627)
    at org.hibernate.event.def.DefaultInitializeCollectionEventListener.onInitializeCollection(DefaultInitializeCollectionEventListener.java:83)
    at org.hibernate.impl.SessionImpl.initializeCollection(SessionImpl.java:1863)
    at org.hibernate.collection.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:369)
    at org.hibernate.collection.AbstractPersistentCollection.read(AbstractPersistentCollection.java:111)
    at org.hibernate.collection.PersistentBag.iterator(PersistentBag.java:272)
    at my.example.persistence.Farm.getAnnimals(Farm.java:132)
    at my.example.DTOFactory.updateFarmDTO(DTOFactory.java:269)
    at my.example.DTOFactory.createFarmDTO(DTOFactory.java:250)
    at my.example.DTOFactory.createChickenDTO(DTOFactory.java:183)
    at my.example.ChickenServiceImpl.createChicken(ChickenServiceImpl.java:62)
    at my.example.ChickenServiceTest.createChickenWithHome(ChickenServiceTest.java:243)
    at my.example.ChickenServiceTest.testRejectChickenHome(ChickenServiceTest.java:186)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    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.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:31)
    at org.junit.runners.BlockJUnit4ClassRunner.runNotIgnored(BlockJUnit4ClassRunner.java:79)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:71)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:49)
    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.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:236)
    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.sql.SQLSyntaxErrorException: incompatible data types in combination
    at org.hsqldb.jdbc.Util.sqlException(Unknown Source)
    at org.hsqldb.jdbc.Util.sqlException(Unknown Source)
    at org.hsqldb.jdbc.JDBCPreparedStatement.<init>(Unknown Source)
    at org.hsqldb.jdbc.JDBCConnection.prepareStatement(Unknown Source)
    at org.hibernate.jdbc.AbstractBatcher.getPreparedStatement(AbstractBatcher.java:534)
    at org.hibernate.jdbc.AbstractBatcher.getPreparedStatement(AbstractBatcher.java:452)
    at org.hibernate.jdbc.AbstractBatcher.prepareQueryStatement(AbstractBatcher.java:161)
    at org.hibernate.loader.Loader.prepareQueryStatement(Loader.java:1700)
    at org.hibernate.loader.Loader.doQuery(Loader.java:801)
    at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:274)
    at org.hibernate.loader.Loader.loadCollection(Loader.java:2166)
    ... 40 more
Caused by: org.hsqldb.HsqlException: incompatible data types in combination
    at org.hsqldb.error.Error.error(Unknown Source)
    at org.hsqldb.error.Error.error(Unknown Source)
    at org.hsqldb.types.BitType.getAggregateType(Unknown Source)
    at org.hsqldb.types.Type.getAggregateType(Unknown Source)
    at org.hsqldb.QuerySpecification.resolveTypesPartOne(Unknown Source)
    at org.hsqldb.QueryExpression.resolveTypesPartOne(Unknown Source)
    at org.hsqldb.QueryExpression.resolveTypes(Unknown Source)
    at org.hsqldb.ParserDQL.XreadTableSubqueryOrNull(Unknown Source)
    at org.hsqldb.ParserDQL.readTableOrSubquery(Unknown Source)
    at org.hsqldb.ParserDQL.XreadTableReference(Unknown Source)
    at org.hsqldb.ParserDQL.XreadFromClause(Unknown Source)
    at org.hsqldb.ParserDQL.XreadTableExpression(Unknown Source)
    at org.hsqldb.ParserDQL.XreadQuerySpecification(Unknown Source)
    at org.hsqldb.ParserDQL.XreadSimpleTable(Unknown Source)
    at org.hsqldb.ParserDQL.XreadQueryPrimary(Unknown Source)
    at org.hsqldb.ParserDQL.XreadQueryTerm(Unknown Source)
    at org.hsqldb.ParserDQL.XreadQueryExpressionBody(Unknown Source)
    at org.hsqldb.ParserDQL.XreadQueryExpression(Unknown Source)
    at org.hsqldb.ParserDQL.compileCursorSpecification(Unknown Source)
    at org.hsqldb.ParserCommand.compilePart(Unknown Source)
    at org.hsqldb.ParserCommand.compileStatement(Unknown Source)
    at org.hsqldb.Session.compileStatement(Unknown Source)
    at org.hsqldb.StatementManager.compile(Unknown Source)
    at org.hsqldb.Session.execute(Unknown Source)
    ... 49 more

---

免责声明：这只是猜测

尝试不进行强制收集初始化。诸如此类：

@Entity
public class Farm implements Serializable{

    @OneToMany(mappedBy = "farm", cascade = { CascadeType.ALL }, targetEntity=AbstractAnimals.class, fetch=FetchType.LAZY)
    private List<AbstractAnimal> animals;

}

@实体
公共类场实现可序列化{
@OneToMany（mappedBy=“farm”，cascade={CascadeType.ALL}，targetEntity=AbstractAnimals.class，fetch=FetchType.LAZY）
私人动物名录；
}

我在这里使用相同的方法，但有一些不同。
也要检查这些内容：

1.在

AbstractAnimal

类中将场的Fetch Type设置为EAGER

@ManyToOne(fetch = FetchType.EAGER)
@JoinColumn(name = "farmId", nullable = false)
private Farm farm;

---

2.将此注释置于getter之上

@xmltransive

我不知道你做错了什么。您只是没有向我们展示足够的代码来检测问题

以下是您如何正确操作的方法：

这是同一个对象模型的实现，但其工作方式很好。有一个Gradle脚本，它将生成并应用相关的SQL；然后，您可以运行Main类来插入和查询一些数据，包括调用

Farm.getanives（）

我的代码和你的代码有一些不同。我的比较简单；我省略了各种不必要的事情，比如指定列名、明确声明集合是惰性的、使实体类可序列化等等。我还选择将

抽象哺乳动物

注释为

@entity

，而不是

@MappedSuperclass

。我觉得没有理由不这样做。我试了两种方法，两种方法都有效

---

所以，不管你出了什么问题，你的代码和我的代码是不同的。这可能是JPA实现中的一个bug。这很可能是注释中的错误。我建议你克隆我的代码，让它运行，然后开始一点一点地修改它，使之更像你的代码，看看它什么时候会崩溃。

好的，多亏了汤姆·安德森，我已经设法解决了我的问题。解决方案是使用Hibernate 4.1而不是3.6，并从

'Session'.connection（）

到

---

您需要显示用于此查询的JPQL。另外，异常中引用的

my.example.persistence.Request

类是什么？很抱歉，代码失序错误。那么什么是JPQL？您在调用entityManager.createQuery（）时使用的查询，还是您刚刚调用了entityManager.find（）？您能否显示打开会话并查询集合的代码段？很难说问题出在哪里，因为您向我们展示的代码不是真正的代码。它甚至不编译，如果要修复编译错误，它将不会描述有效的JPA实体。请尝试注释getter而不是字段。在maven编译期间：无法确定类型：java.util.List，表：Farm，列：[org.hibernate.mapping.Column（动物）]

@Entity
public class Farm implements Serializable{

    @OneToMany(mappedBy = "farm", cascade = { CascadeType.ALL }, targetEntity=AbstractAnimals.class, fetch=FetchType.LAZY)
    private List<AbstractAnimal> animals;

}

@ManyToOne(fetch = FetchType.EAGER)
@JoinColumn(name = "farmId", nullable = false)
private Farm farm;

'Session'.doWork(new Work() {
    @Override
    public void execute(Connection c) throws SQLException {

    }
}