当一个实体映射到另一个在其子类上具有直接实现的实体时,我有一个问题.参见下面的示例映射：
@Entity
class Location {
@OneToOne
@JoinColumn(...)
private Person person;
}
@Entity
@Inheritance(strategy=InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name="person_type",discriminatorType=DiscriminatorType.STRING)
abstract class Person {
}
@Entity
@DiscriminatorValue("M")
class Man extends Person {
...
}
@Entity
@DiscriminatorValue("W")
class Woman extends Person {
...
}
现在,这是我在我的数据库表上：
位置表：
id = 1,person_id = 1
人表：
ID = 1,person_type = “M”
当我使用实体管理器检索位置时,hibernate会抛出一个异常,指出我无法实例化一个抽象类或接口.
Location location = entityManager.find(Location.class,1L);
Hibernate抛出这个错误：
javax.persistence.PersistenceException: org.hibernate.InstantiationException: Cannot instantiate abstract class or interface: Person at org.hibernate.ejb.AbstractEntityManagerImpl.throwPersistenceException(AbstractEntityManagerImpl.java:630) at org.hibernate.ejb.AbstractEntityManagerImpl.find(AbstractEntityManagerImpl.java:195) at ...... 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:585) at org.junit.internal.runners.TestMethod.invoke(TestMethod.java:59) at org.junit.internal.runners.MethodRoadie.runTestMethod(MethodRoadie.java:98) at org.unitils.UnitilsJUnit4TestClassRunner$TestListenerInvokingMethodRoadie.runTestMethod(UnitilsJUnit4TestClassRunner.java:174) at org.junit.internal.runners.MethodRoadie$2.run(MethodRoadie.java:79) at org.junit.internal.runners.MethodRoadie.runBeforesThenTestThenAfters(MethodRoadie.java:87) at org.unitils.UnitilsJUnit4TestClassRunner$TestListenerInvokingMethodRoadie.runBeforesThenTestThenAfters(UnitilsJUnit4TestClassRunner.java:156) at org.junit.internal.runners.MethodRoadie.runTest(MethodRoadie.java:77) at org.junit.internal.runners.MethodRoadie.run(MethodRoadie.java:42) at org.unitils.UnitilsJUnit4TestClassRunner.invokeTestMethod(UnitilsJUnit4TestClassRunner.java:95) at org.junit.internal.runners.JUnit4ClassRunner.runMethods(JUnit4ClassRunner.java:51) at org.unitils.UnitilsJUnit4TestClassRunner.access$000(UnitilsJUnit4TestClassRunner.java:44) at org.unitils.UnitilsJUnit4TestClassRunner$1.run(UnitilsJUnit4TestClassRunner.java:62) at org.junit.internal.runners.ClassRoadie.runUnprotected(ClassRoadie.java:27) at org.junit.internal.runners.ClassRoadie.runProtected(ClassRoadie.java:37) at org.unitils.UnitilsJUnit4TestClassRunner.run(UnitilsJUnit4TestClassRunner.java:68) at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:49) 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)
解决方法
这对我来说是一个窍门,使用hibernate作为持久性提供者.
@OneToOne(cascade = {CascadeType.PERSIST,CascadeType.MERGE})
