Problem with reverse engineering a many-to-one unidirectional association with hibernate tools

Question

I'm using Hibernate tools 3.40 in Eclipse (Helios). I'm trying to generate POJOs from my DB (MSSQL 2008) with EJB3 style (i.e. JPA2.0 annotations).
Let's say I have two tables A and B where there is a foreign key from A to B.
This generates, by default, a POJO for A which has B as a member (its "parent") and a POJO for B which has a Set<A> as a member (its "children").
What I'd like is to know how I can control the rev-eng so that only one side of the association is created (I have different use cases so basically all three options are important for me).
I do not want to use hbm.xml files as I'm working with annotations and JPA2.0 but I can specify some metadata on the reverse engineering process to hibernate via hibernae.reveng.xml

I've tried configuring the foreign-key attribute and defining there the exclude=true but that only provided me with a half an answer for one scenario. That generated an A POJO with a bPK int member which is tolerable and understandable but the generated POJO of B now does not compile as the one-to-many annotation has an invalid attribute; The mappedby="unresolved" due to the fact that A no longer has a property which hibernate reveng can map back to.

So, I currently cannot create uni-directional associations and I'd appreciate any help.

Gotland

Answer 1

Create a class for reveng. strategy at Hibernate Code Generation Configuration

Example :

public class MyReverseEngineeringStrategy extends DelegatingReverseEngineeringStrategy {

   public MyReverseEngineeringStrategy(ReverseEngineeringStrategy delegate) {
       super(delegate);
   }

   @Override
   public void setSettings(ReverseEngineeringSettings settings) {
       super.setSettings(settings);
   }

   @Override
   public boolean excludeForeignKeyAsCollection(String keyname, 
    TableIdentifier fromTable, java.util.List fromColumns, 
    TableIdentifier referencedTable, java.util.List referencedColumns) {

    // TODO : Your work here
    if (keyname.equals("___") && 
        fromTable.getName().equals("___") && 
        fromColumns.contains("___") && 
        referencedTable.getName().equals("___") && 
        referencedColumns.contains("___")) {

        return true;
    }

    return false;
   }
}

JavaDoc for method excludeForeignKeyAsCollection

Should this foreignkey be excluded as a oneToMany 

and there also have another method call excludeForeignKeyAsManytoOne

Should this foreignkey be excluded as a many-to-one 

Relay

Thanks a lot. I wish there was a better way to do this than to hardcode these requirements in that "obscure" class but at least it's a working solution. – Gotland

I have the same problem, but your answer is specific for the "___", it is not a general answer. Thanks anyway – Dotation

Answer 2

Currently (tested with Hibernate Tools 5.2), generating unidirectional many-to-one works.

In the documentation (https://docs.jboss.org/tools/4.0.0.Final/en/hibernatetools/html_single/index.html#hibernaterevengxmlfile), you can see that you can exclude some side of the relationship :

For example (renaming properties)

 <!-- control many-to-one and set names for a specific named foreign key constraint -->
 <foreign-key constraint-name="ORDER_CUST">
   <many-to-one property="customer"/>
   <set property="orders"/>
 </foreign-key>

Or (excluding properties)

 <!-- can also control a pure (shared pk) one-to-one  -->
  <foreign-key constraint-name="ADDRESS_PERSON">
   <one-to-one exclude="false"/>
   <inverse-one-to-one exclude="true"/>
  </foreign-key>

So to have just one side of the relationship with @ManyToOne only, you could do the following :

<table name="city" schema="public">
    <primary-key property="id">
        <key-column name="id" type="integer"/>
    </primary-key>
</table>

<table name="country" schema="public">
    <foreign-key constraint-name="country_capital_fkey" foreign-schema="public">
        <many-to-one property="capital" exclude="false"/>
        <set exclude="true" />
    </foreign-key>
</table>

You can also fetch an instance of my sample database with Docker here :

docker pull ghusta/postgres-world-db:2.1

Dolan