GORM prevent creation of a foreign key constraint for a Domain

Question

I am developing a web based application in Grails. I have come across a situation where I would like to try and suppress GORM from creating a foreign key constraint on a fie

Answer 1

After a relatively short googling I found Burt Beckwith's blog entry: http://burtbeckwith.com/blog/?p=465 that explains the basics of GORM customization. With the following configuration class I managed to prevent creation of a key I did not want to get created. In Burt's example a RootClass is required, but this did not suit my needs so the checking is omitted.

package com.myapp;

import com.myapp.objects.SomeClass;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.codehaus.groovy.grails.orm.hibernate.cfg.GrailsAnnotationConfiguration;
import org.hibernate.MappingException;
import org.hibernate.mapping.ForeignKey;
import org.hibernate.mapping.PersistentClass;
import org.hibernate.mapping.RootClass;

import java.util.Collection;
import java.util.Iterator;

public class DomainConfiguration extends GrailsAnnotationConfiguration {
    private static final long serialVersionUID = 1;

    private boolean _alreadyProcessed;

    @SuppressWarnings({"unchecked", "rawtypes"})
    @Override
    protected void secondPassCompile() throws MappingException {
        super.secondPassCompile();

        if(_alreadyProcessed) {
            return;
        }

        Log log = LogFactory.getLog(DomainConfiguration.class.getName());

        for(PersistentClass pc : (Collection) classes.values()) {
            boolean preventFkCreation = false;
            String fkReferencedEntityNameToPrevent = null;

            if("com.myapp.objects.SomeClassWithUnwantedFkThatHasSomeClassAsAMember".equals(pc.getClassName())) {
                preventFkCreation = true;
                fkReferencedEntityNameToPrevent = SomeClass.class.getName();
            }

            if(preventFkCreation) {
                for(Iterator iter = pc.getTable().getForeignKeyIterator(); iter.hasNext(); ) {
                    ForeignKey fk = (ForeignKey) iter.next();

                    if(fk.getReferencedEntityName().equals(fkReferencedEntityNameToPrevent)) {
                        iter.remove();
                        log.info("Prevented creation of foreign key referencing " + fkReferencedEntityNameToPrevent + " in " + pc.getClassName() + ".");
                    }
                }
            }
        }

        _alreadyProcessed = true;
    }
}

The configuration class is introduced to Grails by putting it to datasource.groovy:

dataSource {
    ...
    ...
    configClass = 'com.myapp.DomainConfiguration
}