Hibernate table with foreign key referring to same table non-primary column returns no result

Question

Given the table with the following columns:

id | parent_api_id | api_id

where the parent_api_id should refer to the api_id of the same table as a OneToMany relationship: one entry should only have one parent, but may have any positive number of subordinates that is referring to it.

I have the following setup:

@Entity
@Table(name="regions")
publicclass Region {

    private Integer id;
    private Region parent;
    private Integer apiId;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id", nullable = false, unique = true)
    public Integer getId() {
        return id;
    }

    public Region setId(Integer id) {
        this.id = id;
        return this;
    }

    @ManyToOne
    @JoinColumn(name = "parent_api_id", referencedColumnName = "api_id")
    public Region getParent() {
        return parent;
    }

    public Region setParent(Region parent) {
        this.parent = parent;
        return this;
    }

    @Column(name="api_id")
    public Integer getApiId() {
        return apiId;
    }

    public Region setApiId(Integer apiId){
        this.apiId = apiId;
        return this;
    }
}

This class will give no results and also no exception, while I expect to see many results returned.

If I comment out the annotations on parent:

//@ManyToOne
//@JoinColumn(name = "parent_api_id", referencedColumnName = "api_id")
public Region getParent() {
    return parent;
}

The same operation will return what I expect, just without the parents infomation.

If I have:

@ManyToOne
@JoinColumn(name = "parent_api_id")//, referencedColumnName = "api_id")
public Region getParent() {
    return parent;
}

Then it will throw exception:

org.hibernate.ObjectNotFoundException: No row with the given identifier exists: [my.app.Region#6131153]
at org.hibernate.impl.SessionFactoryImpl$1.handleEntityNotFound(SessionFactoryImpl.java:375)
at org.hibernate.event.def.DefaultLoadEventListener.load(DefaultLoadEventListener.java:145)
at org.hibernate.event.def.DefaultLoadEventListener.proxyOrLoad(DefaultLoadEventListener.java:195)
at org.hibernate.event.def.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:103)
at org.hibernate.impl.SessionImpl.fireLoad(SessionImpl.java:878)
at org.hibernate.impl.SessionImpl.internalLoad(SessionImpl.java:846)
at org.hibernate.type.EntityType.resolveIdentifier(EntityType.java:557)
at org.hibernate.type.EntityType.resolve(EntityType.java:379)
at org.hibernate.engine.TwoPhaseLoad.initializeEntity(TwoPhaseLoad.java:116)
at org.hibernate.loader.Loader.initializeEntitiesAndCollections(Loader.java:842)
at org.hibernate.loader.Loader.doQuery(Loader.java:717)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:224)
at org.hibernate.loader.Loader.doList(Loader.java:2211)
at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2095)
at org.hibernate.loader.Loader.list(Loader.java:2090)
at org.hibernate.loader.criteria.CriteriaLoader.list(CriteriaLoader.java:95)
at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1569)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at org.hibernate.context.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:301)
at com.sun.proxy.$Proxy31.list(Unknown Source)
at org.hibernate.impl.CriteriaImpl.list(CriteriaImpl.java:283)
at com.wewherego.api.malloc.domain.repositories.PlaceRepository.invokeQuery(PlaceRepository.java:81)
at com.wewherego.api.malloc.domain.repositories.PlaceRepository.search(PlaceRepository.java:50)
at com.wewherego.api.malloc.controllers.RegionsController.search(RegionsController.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:497)
at org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:215)
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:132)
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:781)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:721)
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:83)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:943)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:877)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:966)
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:857)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:842)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at com.wewherego.api.malloc.infrastructure.CORSFilter.doFilter(CORSFilter.java:23)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1041)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:603)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)

Which I would understand why: it default to look for id of #6023506 instead of the api_id, while it actually suppose to map to api_id.

So in my first approach, what did I do wrong?

Answer 1

Making the Region class implement Serializable should help.

Quote from jboss docs link when using referencedColumnName to a non primary key column, the associated class has to be Serializable.

Made the Region class Serializable as below:

@Entity
@Table(name="regions")
class Region  implements Serializable{

    private Integer id;
    private Region parent;
    private Integer apiId;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id", nullable = false, unique = true)
    public Integer getId() {
        return id;
    }

    @ManyToOne
    @JoinColumn(name = "parent_api_id", referencedColumnName = "api_id")
    public Region getParent() {
        return parent;
    }
// Remaining getters/setters
}

And with this I see that I am able to retrieve Region object with properly populated parent_api_id and api_id with following test code.

        Session session = openSession();
        Transaction tx = session.beginTransaction();
        Region r1 = new Region();
        r1.setApiId(40);
        session.persist(r1);

        Region r2 = new Region();
        r2.setApiId(20);
        r2.setParent(r1);

        Region r3 = new Region();
        r3.setApiId(30);
        r3.setParent(r1);

        session.persist(r2);
        session.persist(r3);
        tx.commit();

        Session session1 = openSession();
        Transaction tx1 = session1.beginTransaction();
        Region r = session1.get(Region.class, r3.getId());
        //OR Region r = (Region) session1.createCriteria(Region.class).add(Restrictions.eq("id", r3.getId())).uniqueResult();

results in following join query

select
    region0_.id as id1_0_0_,
    region0_.api_id as api_id2_0_0_,
    region0_.parent_api_id as parent_a3_0_0_,
    region1_.id as id1_0_1_,
    region1_.api_id as api_id2_0_1_,
    region1_.parent_api_id as parent_a3_0_1_ 
from
    regions region0_ 
left outer join
    regions region1_ 
        on region0_.parent_api_id=region1_.api_id 
where
    region0_.id=?

OUTPUT Region id - 3, Region API id - 30, Parent id - 1, Parent API id - 40

Hope I have not misinterpreted the question.