Question

我有这两个类：

@Entity
public class Tag {

    @Id @GeneratedValue(strategy = GenerationType.AUTO)
    private long id;

    @OneToMany(cascade = CascadeType.ALL, orphanRemoval = true, mappedBy = "parent")
    private List<TagValue> values;

    private String name;
}

@Entity
public class TagValue {

    @Id @GeneratedValue(strategy = GenerationType.AUTO)
    private long id;

    private String name;

    @ManyToOne
    private Tag parent;
}

这两个是父母子女关系，孩子知道它的父母。当我尝试删除父级并且子级仍然引用它时，我的问题就出现了。 Eclipse Link告诉我，我违反了外键约束，因为子（TagValue）仍在引用它。当孩子仍然引用父母时，我如何更改当前的方法以删除父母？

最后，如何在删除父项时告诉JPA删除所有引用父项的子项？它必须像这样工作。我知道，如果父母知道孩子使用列表会更容易，但这并不是我所追求的。我玩过级联等等，但我似乎没有得到它。

编辑：

所以我被告知，它应该已经可以使用我的代码了。由于它没有，这里是失败的用例和错误的堆栈跟踪。

TagValue value = new TagValue();
value.setName("Testvalue");

Tag tag = new Tag();
tag.setName("Testtag");
value.setParent(tag);
Database.addTag(tag);
Database.addTagValue(value);
Database.removeTag(tag);

Database类方法定义如下：

public static void addTag(final Tag tag) throws Exception {
    manager.getTransaction().begin();
    manager.persist(tag);
    manager.getTransaction().commit();
}

public static void addTagValue(final TagValue value) throws Exception {
    manager.getTransaction().begin();
    manager.persist(value);
    manager.getTransaction().commit();
}

public static void removeTag(final Tag tag) throws Exception {
    manager.getTransaction().begin();
    manager.remove(tag);
    manager.getTransaction().commit();
}

stacktrace：

注意：Auf Schlüssel (id)=(1) wird noch aus Tabelle „tagvalue“表示表{tag>中仍然引用了键(id)=(1)。

[EL Warning]: 2015-02-24 11:12:43.785--UnitOfWork(390138887)--Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.5.2.v20140319-9ad6abd): org.eclipse.persistence.exceptions.DatabaseException
Internal Exception: org.postgresql.util.PSQLException: FEHLER: Aktualisieren oder Löschen in Tabelle „tag“ verletzt Fremdschlüssel-Constraint „fk_tagvalue_parent_id“ von Tabelle „tagvalue“
  Detail: Auf Schlüssel (id)=(1) wird noch aus Tabelle „tagvalue“ verwiesen.
Error Code: 0
Call: DELETE FROM TAG WHERE (ID = ?)
    bind => [1 parameter bound]
Query: DeleteObjectQuery(Tag(id=1, values=[], name=Testtag))
javax.persistence.RollbackException: Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.5.2.v20140319-9ad6abd): org.eclipse.persistence.exceptions.DatabaseException
Internal Exception: org.postgresql.util.PSQLException: FEHLER: Aktualisieren oder Löschen in Tabelle „tag“ verletzt Fremdschlüssel-Constraint „fk_tagvalue_parent_id“ von Tabelle „tagvalue“
  Detail: Auf Schlüssel (id)=(1) wird noch aus Tabelle „tagvalue“ verwiesen.
Error Code: 0
Call: DELETE FROM TAG WHERE (ID = ?)
    bind => [1 parameter bound]
Query: DeleteObjectQuery(Tag(id=1, values=[], name=Testtag))
    at org.eclipse.persistence.internal.jpa.transaction.EntityTransactionImpl.commit(EntityTransactionImpl.java:157)
    at de.yabue.baka.YabueCentral.Persistence.Database.removeTag(Database.java:256)
    at de.yabue.baka.YabueCentral.Persistence.DatabaseTest.testPersistence(DatabaseTest.java:50)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:74)
    at org.testng.internal.Invoker.invokeMethod(Invoker.java:673)
    at org.testng.internal.Invoker.invokeTestMethod(Invoker.java:846)
    at org.testng.internal.Invoker.invokeTestMethods(Invoker.java:1170)
    at org.testng.internal.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:125)
    at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:109)
    at org.testng.TestRunner.runWorkers(TestRunner.java:1147)
    at org.testng.TestRunner.privateRun(TestRunner.java:749)
    at org.testng.TestRunner.run(TestRunner.java:600)
    at org.testng.SuiteRunner.runTest(SuiteRunner.java:317)
    at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:312)
    at org.testng.SuiteRunner.privateRun(SuiteRunner.java:274)
    at org.testng.SuiteRunner.run(SuiteRunner.java:223)
    at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:52)
    at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:86)
    at org.testng.TestNG.runSuitesSequentially(TestNG.java:1039)
    at org.testng.TestNG.runSuitesLocally(TestNG.java:964)
    at org.testng.TestNG.run(TestNG.java:900)
    at org.testng.remote.RemoteTestNG.run(RemoteTestNG.java:110)
    at org.testng.remote.RemoteTestNG.initAndRun(RemoteTestNG.java:205)
    at org.testng.remote.RemoteTestNG.main(RemoteTestNG.java:174)
    at org.testng.RemoteTestNGStarter.main(RemoteTestNGStarter.java:125)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:134)
Caused by: Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.5.2.v20140319-9ad6abd): org.eclipse.persistence.exceptions.DatabaseException
Internal Exception: org.postgresql.util.PSQLException: FEHLER: Aktualisieren oder Löschen in Tabelle „tag“ verletzt Fremdschlüssel-Constraint „fk_tagvalue_parent_id“ von Tabelle „tagvalue“
  Detail: Auf Schlüssel (id)=(1) wird noch aus Tabelle „tagvalue“ verwiesen.
Error Code: 0
Call: DELETE FROM TAG WHERE (ID = ?)
    bind => [1 parameter bound]
Query: DeleteObjectQuery(Tag(id=1, values=[], name=Testtag))
    at org.eclipse.persistence.exceptions.DatabaseException.sqlException(DatabaseException.java:340)
    at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.processExceptionForCommError(DatabaseAccessor.java:1611)
    at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.executeDirectNoSelect(DatabaseAccessor.java:898)
    at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.executeNoSelect(DatabaseAccessor.java:962)
    at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.basicExecuteCall(DatabaseAccessor.java:631)
    at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.executeCall(DatabaseAccessor.java:558)
    at org.eclipse.persistence.internal.sessions.AbstractSession.basicExecuteCall(AbstractSession.java:2002)
    at org.eclipse.persistence.sessions.server.ClientSession.executeCall(ClientSession.java:298)
    at org.eclipse.persistence.internal.queries.DatasourceCallQueryMechanism.executeCall(DatasourceCallQueryMechanism.java:242)
    at org.eclipse.persistence.internal.queries.DatasourceCallQueryMechanism.executeCall(DatasourceCallQueryMechanism.java:228)
    at org.eclipse.persistence.internal.queries.DatasourceCallQueryMechanism.deleteObject(DatasourceCallQueryMechanism.java:210)
    at org.eclipse.persistence.internal.queries.StatementQueryMechanism.deleteObject(StatementQueryMechanism.java:104)
    at org.eclipse.persistence.queries.DeleteObjectQuery.executeDatabaseQuery(DeleteObjectQuery.java:218)
    at org.eclipse.persistence.queries.DatabaseQuery.execute(DatabaseQuery.java:899)
    at org.eclipse.persistence.queries.DatabaseQuery.executeInUnitOfWork(DatabaseQuery.java:798)
    at org.eclipse.persistence.queries.ObjectLevelModifyQuery.executeInUnitOfWorkObjectLevelModifyQuery(ObjectLevelModifyQuery.java:108)
    at org.eclipse.persistence.queries.DeleteObjectQuery.executeInUnitOfWorkObjectLevelModifyQuery(DeleteObjectQuery.java:119)
    at org.eclipse.persistence.queries.ObjectLevelModifyQuery.executeInUnitOfWork(ObjectLevelModifyQuery.java:85)
    at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.internalExecuteQuery(UnitOfWorkImpl.java:2896)
    at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1804)
    at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1786)
    at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1737)
    at org.eclipse.persistence.internal.sessions.CommitManager.deleteAllObjects(CommitManager.java:336)
    at org.eclipse.persistence.internal.sessions.CommitManager.deleteAllObjects(CommitManager.java:285)
    at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.commitToDatabase(UnitOfWorkImpl.java:1444)
    at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.commitToDatabaseWithChangeSet(UnitOfWorkImpl.java:1531)
    at org.eclipse.persistence.internal.sessions.RepeatableWriteUnitOfWork.commitRootUnitOfWork(RepeatableWriteUnitOfWork.java:277)
    at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.commitAndResume(UnitOfWorkImpl.java:1169)
    at org.eclipse.persistence.internal.jpa.transaction.EntityTransactionImpl.commit(EntityTransactionImpl.java:132)
    ... 33 more
Caused by: org.postgresql.util.PSQLException: FEHLER: Aktualisieren oder Löschen in Tabelle „tag“ verletzt Fremdschlüssel-Constraint „fk_tagvalue_parent_id“ von Tabelle „tagvalue“
  Detail: Auf Schlüssel (id)=(1) wird noch aus Tabelle „tagvalue“ verwiesen.
    at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2103)
    at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1836)
    at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:257)
    at org.postgresql.jdbc2.AbstractJdbc2Statement.execute(AbstractJdbc2Statement.java:512)
    at org.postgresql.jdbc2.AbstractJdbc2Statement.executeWithFlags(AbstractJdbc2Statement.java:388)
    at org.postgresql.jdbc2.AbstractJdbc2Statement.executeUpdate(AbstractJdbc2Statement.java:334)
    at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.executeDirectNoSelect(DatabaseAccessor.java:890)
    ... 59 more

我还尝试在删除之前先从数据库中删除要删除的标记，但返回的实例在values列表中没有任何项目。所以我最后的猜测是，我必须填写清单values吗？

Answer 1

就像我最后的想法一样，我必须自己填写父母的名单。所以现在不再有错误了。

我改变了这个方法：

public static void addTagValue(final TagValue value) throws Exception {
    manager.getTransaction().begin();
    manager.persist(value);
    manager.getTransaction().commit();
}

为：

public static void addTagValue(final TagValue value) throws Exception {
    manager.getTransaction().begin();
    value.getParent().getValues().add(value);
    manager.persist(value);
    manager.getTransaction().commit();
}

这就是为什么我之前没有考虑过这个问题：首先，我以某种方式认为，mappedBy会自动完成工作。此外，我使用lombok生成我的setter和getter，并在@Data注释上执行此操作。此注释生成了所有setter和getter，还生成了toString()和hashCode()方法。当我将一个项添加到values列表时，hashCode()方法产生了一个Stackoverflow，我必须首先解决它。

JPA删除＆＃34; one＆＃34;在多对一的关系中

1 个答案: