Primary key based on multiple fields which are of a custom class type

Question

Hello!
I have the following two classes.
public class Application
protected String appName;
protected Set moduleOptions = new HashSet(); //Set<ModuleOption>
public class Option
protected String name;
protected Application application;
Now, I need for Option to have a composite primary key based on both its
fields. How do I do this?
For starters, I just need a few hints on how this should be done in Kodo
because I already have this thing working in JPOX and that solution does
not map directly to Kodo. JPOX defines the OptionPK (primary key class)
to contain field ApplicationPK, and not Application. But Kodo does not
accept this because of a mismatch between fields in class and its primary
key class. (Not implying that Kodo should accept the same kind of
solution.)
Btw, I'm evaluating version 3.2.3.
Thanks in advance!

Answer 1

Viktor,
The typical Kodo pattern for doing this is to create a private field in
Option for each primary key in Application, map those fields as
primary-key (but not the field of type Application), and therefore put
those fields in the OptionPK. These fields should then be mapped to the
same columns as the Application reference. Then, set the primary key
fields to the same value as they are in the related object.
Kodo allows multiple fields to be mapped to the same column in the
database, and throws an exception if your actions would set the column
to different values. So, typically, this might look like:
public class Application
protected String appName; // I'm assuming that this is the PK
protected Set moduleOptions = new HashSet ();
public class Option
protected String name; // pk
protected Application application; // not pk
private String applicationAppName; // pk
public Option (String n, Application a)
name = n;
application = a;
applicationAppName = a.appName;
-Patrick
Viktor Matic wrote:
Hello!
I have the following two classes.
public class Application
protected String appName;
protected Set moduleOptions = new HashSet(); //Set<ModuleOption>
public class Option
protected String name;
protected Application application;
Now, I need for Option to have a composite primary key based on both its
fields. How do I do this?
For starters, I just need a few hints on how this should be done in Kodo
because I already have this thing working in JPOX and that solution does
not map directly to Kodo. JPOX defines the OptionPK (primary key class)
to contain field ApplicationPK, and not Application. But Kodo does not
accept this because of a mismatch between fields in class and its primary
key class. (Not implying that Kodo should accept the same kind of
solution.)
Btw, I'm evaluating version 3.2.3.
Thanks in advance!