Doubt in Mikalai Zaikin study guide !!

[Balaji Natarajan]

Please tell me whether the data will get deleted in the database on calling the remove() on the collection returned in the EntityBean below.



public abstract class CustomerBean implements javax.ejb.EntityBean {
...
public void addPhoneNumber(String number, byte type)
throws NamingException, CreateException {
InitialContext jndiEnc = new InitialContext();
PhoneHomeLocal phoneHome = (PhoneHomeLocal)
(jndiEnc.lookup("PhoneHomeLocal"));
PhoneLocal phone = phoneHome.create(number,type);
Collection phoneNumbers = this.getPhoneNumbers();
phoneNumbers.add(phone);
}

public void removePhoneNumber(byte typeToRemove) {
Collection phoneNumbers = this.getPhoneNumbers();
Iterator iterator = phoneNumbers.iterator();
while(iterator.hasNext()){
PhoneLocal phone = (PhoneLocal)iterator.next();
if (phone.getType() == typeToRemove) {
phoneNumbers.remove(phone);
break;
}
}
}

public abstract java.util.Collection getPhoneNumbers( );
public abstract void setPhoneNumbers(java.util.Collection phones);

}

[Roger Chung-Wee]

Not sure, but I would think that remove() just removes the element from the collection. It is actually the add() method which changes the DB.

In a one-to-many relationship, just invoking add() causes the phone to be first removed. So, in order to correctly add a phone, you must first invoke removePhoneNumber() followed by addPhoneNumber().

[Dale Seng]

I don't think HFEJB got into it too deeply, but I do think that for CMP beans, someEBObjectWithRelationship.remove(someEBObjectInRelationship) on an entity bean actually removes it from the database. Of course if you are just spinning through a collection of non-EB's, and you run remove it's not going to do anything to the database.

The examples are horrific (with A's and B's, 1's and 2's)* but this page goes into it very extensively.

--Dale--

* I had to re-write the examples with John, Paul, George and Ringo related to various instruments before I could really 'see' the relationships.
[ May 15, 2004: Message edited by: Dale Seng ]