Use Custom Generator #GenericGenerator for multiple entities with Association - spring-boot

Question

I have two Java Classes:
The first Class Class1 Looks like this:
#Entity
#Table(catalog = "mydb", schema = "dbo", name = "[myTable1]")
#Getter
#Setter
#Builder
#ToString(onlyExplicitlyIncluded = true)
#AllArgsConstructor
#NoArgsConstructor
public class Class1 {
#Id
#Column(name = "ID")
#GeneratedValue(generator = "myGen")
#GenericGenerator(name = "myGen",
strategy = "Y.X.z.generator.MyGen")
private Long id;
#Column(name = "TEXT")
private String text;
#ManyToOne(cascade = CascadeType.ALL)
#JoinColumn(name = "ID")
private Class2 class2;
The second Class Class2 Looks like this
#Entity
#Table(catalog = "mydb", schema = "dbo", name = "[myTable2]")
#Getter
#Setter
#Builder
#ToString(onlyExplicitlyIncluded = true)
#AllArgsConstructor
#NoArgsConstructor
public class Class2 {
#Id
#Column(name = "ID")
#GeneratedValue(generator = "myGen")
#GenericGenerator(name = "myGen",
strategy = "de.svg.releasenotes.generator.MyGen")
private Long id;
#Column(name = "TEXT")
private String text;
As you can see that Class 1 has an association ManyToOne against Class 2.
Class 1 as well as Class 2 use the same GenericGenerator ( Y.X.z.generator.MyGen ).
The Generator looks like this:
import org.hibernate.HibernateException;
import org.hibernate.engine.spi.SharedSessionContractImplementor;
import org.hibernate.id.IdentifierGenerator;
import java.io.Serializable;
import java.util.stream.Stream;
public class MyGen implements IdentifierGenerator {
#Override
public Serializable generate(
SharedSessionContractImplementor session, Object obj)
throws HibernateException {
String query = String.format("select %s from %s",
session.getEntityPersister(obj.getClass().getName(), obj)
.getIdentifierPropertyName(),
obj.getClass().getSimpleName());
Stream<Long> ids = session.createQuery(query).stream();
Long max = ids.max(Long::compare).orElse(0L);
return max + 1;
}
}
The generator makes retrieves the max ID from the DB.TableX and increments it at 1.
When I call my POST endpoint I get the following error:
2022-11-15 15:27:26.214 ERROR 276510 --- [io-13778-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet] : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Handler dispatch failed; nested exception is java.lang.StackOverflowError] with root cause
java.lang.StackOverflowError: null
at org.apache.logging.slf4j.SLF4JLogger.isEnabledFor(SLF4JLogger.java:213) ~[log4j-to-slf4j-2.17.2.jar:2.17.2]
at org.apache.logging.slf4j.SLF4JLogger.isEnabled(SLF4JLogger.java:121) ~[log4j-to-slf4j-2.17.2.jar:2.17.2]
at org.apache.logging.log4j.spi.AbstractLogger.isEnabled(AbstractLogger.java:1513) ~[log4j-api-2.17.2.jar:2.17.2]
at org.jboss.logging.Log4j2Logger.isEnabled(Log4j2Logger.java:46) ~[jboss-logging-3.4.3.Final.jar:3.4.3.Final]
at org.jboss.logging.Logger.isTraceEnabled(Logger.java:98) ~[jboss-logging-3.4.3.Final.jar:3.4.3.Final]
at org.jboss.logging.DelegatingBasicLogger.isTraceEnabled(DelegatingBasicLogger.java:54) ~[jboss-logging-3.4.3.Final.jar:3.4.3.Final]
at org.hibernate.engine.internal.Cascade.cascade(Cascade.java:86) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.event.internal.AbstractFlushingEventListener.cascadeOnFlush(AbstractFlushingEventListener.java:159) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.event.internal.AbstractFlushingEventListener.prepareEntityFlushes(AbstractFlushingEventListener.java:149) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.event.internal.AbstractFlushingEventListener.flushEverythingToExecutions(AbstractFlushingEventListener.java:82) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.event.internal.DefaultAutoFlushEventListener.onAutoFlush(DefaultAutoFlushEventListener.java:50) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.event.service.internal.EventListenerGroupImpl.fireEventOnEachListener(EventListenerGroupImpl.java:107) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.internal.SessionImpl.autoFlushIfRequired(SessionImpl.java:1372) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.internal.SessionImpl.list(SessionImpl.java:1452) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.query.internal.AbstractProducedQuery.doList(AbstractProducedQuery.java:1649) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.query.internal.AbstractProducedQuery.list(AbstractProducedQuery.java:1617) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at Y.X.z.generator.MyGen.generate(MyGen.java:25) ~[classes/:na]
at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:115) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.event.internal.DefaultPersistEventListener.entityIsTransient(DefaultPersistEventListener.java:185) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:128) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.event.service.internal.EventListenerGroupImpl.fireEventOnEachListener(EventListenerGroupImpl.java:118) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.internal.SessionImpl.persistOnFlush(SessionImpl.java:801) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.engine.spi.CascadingActions$8.cascade(CascadingActions.java:341) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.engine.internal.Cascade.cascadeToOne(Cascade.java:510) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.engine.internal.Cascade.cascadeAssociation(Cascade.java:434) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.engine.internal.Cascade.cascadeProperty(Cascade.java:220) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.engine.internal.Cascade.cascade(Cascade.java:153) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.event.internal.AbstractFlushingEventListener.cascadeOnFlush(AbstractFlushingEventListener.java:159) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.event.internal.AbstractFlushingEventListener.prepareEntityFlushes(AbstractFlushingEventListener.java:149) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.event.internal.AbstractFlushingEventListener.flushEverythingToExecutions(AbstractFlushingEventListener.java:82) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.event.internal.DefaultAutoFlushEventListener.onAutoFlush(DefaultAutoFlushEventListener.java:50) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.event.service.internal.EventListenerGroupImpl.fireEventOnEachListener(EventListenerGroupImpl.java:107) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.internal.SessionImpl.autoFlushIfRequired(SessionImpl.java:1372) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.internal.SessionImpl.list(SessionImpl.java:1452) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.query.internal.AbstractProducedQuery.doList(AbstractProducedQuery.java:1649) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.query.internal.AbstractProducedQuery.list(AbstractProducedQuery.java:1617) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at Y.X.z.generator.MyGen.generate(MyGen.java:25) ~[classes/:na]
at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:115) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.event.internal.DefaultPersistEventListener.entityIsTransient(DefaultPersistEventListener.java:185) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:128) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.event.service.internal.EventListenerGroupImpl.fireEventOnEachListener(EventListenerGroupImpl.java:118) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.internal.SessionImpl.persistOnFlush(SessionImpl.java:801) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.engine.spi.CascadingActions$8.cascade(CascadingActions.java:341) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.engine.internal.Cascade.cascadeToOne(Cascade.java:510) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.engine.internal.Cascade.cascadeAssociation(Cascade.java:434) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.engine.internal.Cascade.cascadeProperty(Cascade.java:220) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.engine.internal.Cascade.cascade(Cascade.java:153) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.event.internal.AbstractFlushingEventListener.cascadeOnFlush(AbstractFlushingEventListener.java:159) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.event.internal.AbstractFlushingEventListener.prepareEntityFlushes(AbstractFlushingEventListener.java:149) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.event.internal.AbstractFlushingEventListener.flushEverythingToExecutions(AbstractFlushingEventListener.java:82) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.event.internal.DefaultAutoFlushEventListener.onAutoFlush(DefaultAutoFlushEventListener.java:50) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.event.service.internal.EventListenerGroupImpl.fireEventOnEachListener(EventListenerGroupImpl.java:107) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.internal.SessionImpl.autoFlushIfRequired(SessionImpl.java:1372) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.internal.SessionImpl.list(SessionImpl.java:1452) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.query.internal.AbstractProducedQuery.doList(AbstractProducedQuery.java:1649) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
at org.hibernate.query.internal.AbstractProducedQuery.list(AbstractProducedQuery.java:1617) ~[hibernate-core-5.6.12.Final.jar:5.6.12.Final]
...
Which shows that MyGen has a StackOverflowError.
Any ideas how I can work around my problem?
Thanks a lot.

Answer 1

From the stack trace, it seems like you may have found a bug in hibernate, but it is hard to tell.
The good news is that, if I understand what you are trying to do correctly, you don't need a custom generator, which means you should be able to work around your problem.
You can use the SEQUENCE generation strategy to achieve monotonically increasing ids for your entities:
...
public class Class1 {
#Id
#Column(name = "ID")
#GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "class1_generator")
#SequenceGenerator(name="class1_generator")
private Long id;
...
...
public class Class2 {
#Id
#Column(name = "ID")
#GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "class2_generator")
#SequenceGenerator(name="class2_generator")
private Long id;
...