Bidirectional @OneToOne mapping fails

carlsz · **Joined:** Thu Mar 16, 2006 7:03 pm **Posts:** 3

Hello all:

I'm in the process of migrating my project from XML mapping files to annotations and I've hit a snag. My attempt to map the Stream and Prices objects together results in the exception below. Excerpts from the XML mapping files that I am attempting to replicate as well as the annotations as I have them currently defined are included below. I've also attempted to define the targetEntity for the OneToOne relationship with no luck. Any insight into the problem is appreciated.

Thanks in advance.

Carl

Hibernate version: Hibernate 3.2.2, Hibernate Annotations 3.3

Mapping XML:

Prices.hbm.xml:

Code:

   <class name="Prices" table="stream_prices">
      <id name="id" type="long" column="stream_id">
         <generator class="foreign">
            <param name="property">stream</param>
         </generator>
      </id>
      <one-to-one name="stream" class="Stream" constrained="true" />
      ...
   </class>
   

Stream.hbm.xml:

Code:

   <class name="Stream" table="streams">
      <id name="id" type="long" column="id">
         <generator class="native"/>
      </id>
      ...   
      <one-to-one name="prices" class="Prices" />
      ...
   </class>
   

Annotations:

Prices.java:

Code:

      @Id
      @GeneratedValue(generator="fk")
      @GenericGenerator(
         name="fk",
         strategy="foreign",
         parameters={
            @Parameter(name="property", value="stream")
         }
      )
      @Column(name="stream_id", nullable=false)
      private Long id;
      
      @OneToOne(mappedBy="prices")
      private Stream stream;
   

Stream.java:

Code:

      @Id @GeneratedValue
      @Column(name="id", nullable=false)
      private Long id;
      
      @OneToOne(cascade = CascadeType.ALL)
      @PrimaryKeyJoinColumn
      private Prices prices;
   

Full stack trace of any exception that occurs:

Code:

   org.hibernate.AnnotationException: Unknown mappedBy in: entity.Prices.stream, referenced property unknown: entity.Stream.prices
   at org.hibernate.cfg.OneToOneSecondPass.doSecondPass(OneToOneSecondPass.java:127)
   at org.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:1049)
   at org.hibernate.cfg.AnnotationConfiguration.secondPassCompile(AnnotationConfiguration.java:302)
   at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1205)
   at org.springframework.orm.hibernate3.LocalSessionFactoryBean.newSessionFactory(LocalSessionFactoryBean.java:805)
   at org.springframework.orm.hibernate3.LocalSessionFactoryBean.buildSessionFactory(LocalSessionFactoryBean.java:745)
   at org.springframework.orm.hibernate3.AbstractSessionFactoryBean.afterPropertiesSet(AbstractSessionFactoryBean.java:134)
   at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1175)
   at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1145)
   at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:427)
   at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:251)
   at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:144)
   at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:248)
   at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:160)
   at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:276)
   at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:360)
   at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:241)
   at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:184)
   at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:49)
   at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:3729)
   at org.apache.catalina.core.StandardContext.start(StandardContext.java:4187)
   at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:759)
   at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:739)
   at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:524)
   at org.apache.catalina.startup.HostConfig.deployDescriptor(HostConfig.java:608)
   at org.apache.catalina.startup.HostConfig.deployDescriptors(HostConfig.java:535)
   at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:470)
   at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1122)
   at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:310)
   at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119)
   at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1021)
   at org.apache.catalina.core.StandardHost.start(StandardHost.java:718)
   at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1013)
   at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:442)
   at org.apache.catalina.core.StandardService.start(StandardService.java:450)
   at org.apache.catalina.core.StandardServer.start(StandardServer.java:709)
   at org.apache.catalina.startup.Catalina.start(Catalina.java:551)
   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.apache.catalina.startup.Bootstrap.start(Bootstrap.java:294)
   at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:432)
   

Name and version of the database you are using: MySQL 5.0.22

carlsz · **Joined:** Thu Mar 16, 2006 7:03 pm **Posts:** 3

In continuing to work on the issue, I've removed the @OneToOne(mappedBy="prices") annotation from Stream.java. While the schema is now generated and no exceptions are thrown, 2 interesting things have occurred. The prices table is created correctly with the PK using the stream id, however the foreign key constraint is not created. Also there is now a TINYBLOB column for the stream entry in the prices table because I do not have it annotated. If I annotate the stream field with @Transient, the TINYBLOB column is not created anymore. Here are the annotations as they are currently defined:

Stream.java:

Code:

    @OneToOne(cascade = CascadeType.ALL, optional=false)
    @PrimaryKeyJoinColumn
    private Prices prices;

Prices.java

Code:

    @Id
    @GeneratedValue(generator="fk")
    @GenericGenerator(
        name="fk",
        strategy="foreign",
        parameters={
            @Parameter(name="property", value="stream")
        }
    )
    @Column(name="stream_id", nullable=false, unique=true)
    private Long id;

    @Transient
    private Stream stream;

In referencing THE book, chapter 7 deals with the OneToOne mapping, however they do not discuss the correct way to annotate the field to enable the bidirectional relationship. How should I be annotating the stream field so that the relationship is truly bidirectional? And why is the foreign key constraint not being created?

TIA,
Carl

andydale · **Posted:** Thu Jun 21, 2007 4:17 am

Hi,

From my unnder standing of chapter 7, a bidirectional relationship is based on FK and not shared PKs (or at least it does not document how to do it with shared pks). If it is not an issue to have a fk based relationship do the following:

in prices.java

Code:

@Id
@GeneratedValue
Long id;

@OneToOne(mappedBy="prices") 
private Stream stream;

and in Stream.java

Code:

@OneToOne(cascade = CascadeType.ALL) 
@JoinColumn(name = "<name for column>")
 private Prices prices;

Cheers,

Andy

carlsz · **Joined:** Thu Mar 16, 2006 7:03 pm **Posts:** 3

Thanks for your response Andy. If you take a look at the mapping xml file snippets in my first post, you'll note that the table structure created should resemble something like the diagram found in figure 7.2 of chapter 7 and the example below.

Code:

+---------------+
|  <<Table>>    |
|   streams     |
+---------------+
|  id <<PK>>    |
+---------------+

Code:

+---------------------------+
|         <<Table>>         |
|     stream_prices         |
+---------------------------+
|  stream_id <<PK>> <<FK>>  |
+---------------------------+

And it is exactly this sort of thing that I am attempting to do with annotations. I can reproduce the table structure, however the foreign key constraint is not created by Hibernate at all while using annotations. I would have assumed that defining the GenericGenerator using the foreign strategy would take care of this. Unfortunately this is not the case. Can this actually be accomplished using annotations? Given that I am migrating an existing project to annotations, I'd prefer not to change the table structure.

Thanks.
Carl