What is the best way to map this?

dtam · **Joined:** Tue Jan 06, 2004 4:51 pm **Posts:** 48

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Hibernate version:3.2.0rc2

Name and version of the database you are using:PostgreSQL 8.0

I have three tables:

Code:

report (id serial not null primary key)

parameter (id serial not null primary key)

report_parameter (report_id integer fk, parameter_id integer fk, required boolean not null default false)

I want to map this into two classes, Report (Integer id, List parameters) and Parameter(Integer id, Boolean required). Is this possible? Or do I have to create a third class to ReportParameter(Report report, Parameter parameter, Boolean required)?

Thanks in advance.

tenwit · **Joined:** Thu Dec 23, 2004 9:08 pm **Posts:** 2008

It's not directly possible, but it's easy to fake it. Set it up as a <set> containing a <composite-element>, which in turn contains a <property> and a <many-to-one unique="true">. Specify the composite-element class as Property, and the many-to-one class as PropertyValue or somesuch. Then in the Property class, which contains the a PropertyValue member, use delegation to provide API access to the PropertyValue properties. Hibernate will use getPropertyValue(), but the API user will use isRequired(), which returns getPropertyValue().isRequired().

dtam · **Joined:** Tue Jan 06, 2004 4:51 pm **Posts:** 48

Thanks for the reply. I think that's what I tried doing (I am using Annotations), but I did something wrong. Can you please post a code example?

What I tried doing was:

Code:

@Entity
public class Report implements Serializable {
@Id
public Integer getId() {...}

@OneToMany
@Embedded
@AttributeOverrides){
      @AttributeOverride(name="required", column=@Column(name="required"))
})
public List<Parameter> getParameter() {...}
}

@Entity @Embeddable
public class Parameter implements Serializable {
@Id public Integer getId(){...}
public Boolean getRequired() {...}
}

Sorry... I am quite new to annotations so I'm probably doing something silly.

tenwit · **Joined:** Thu Dec 23, 2004 9:08 pm **Posts:** 2008

I'm afraid I know next to nothing about EJB3 annotations. I know that you'll need to specify the ParameterValue class (or whatever you're going to call the class that is in the many-to-one relationship with the embeddable Parameter class). You'll also have to mark as @Transient the Required property in the Parameter class, because that's not mapped (it gets its value from the Required property in the embedded ParameterValue class).

BTW I believe that the javabean convention for property accessors that return a boolean/Boolean value is "is<propname>", not "get<propname>".

dtam · **Joined:** Tue Jan 06, 2004 4:51 pm **Posts:** 48

I thought it was get for Boolean (since it can be null) and is for boolean. I just use the Netbeans refactoring to generate my accessors and it just uses get, anyway.

Thanks for the help.. I'll play around with it.

dtam · **Joined:** Tue Jan 06, 2004 4:51 pm **Posts:** 48

I've played around with it, even trying @CollectionOfElements with @Embeddable and @SecondaryTable, but I still couldn't get it to work.

Does anyone have an annotation example that could help?