RE: Digester and inheritance

[Galbreath, Mark]

You are misusing inheritance.  Instead of extending Component, give
HelperClass (was ChildClass) a private field that references an instance of
Component (a design pattern known as "composition").Each instance method in
HelperClass invokes the corresponding method on the contained instance of
Component and returns the results (a design pattern known as "forwarding"):

public class HelperClass {
    private final Component c;
    public void setName( String name) {
        c.setName( name);
    }
    public String getName() {
        return c.getName();
    }
}

Cheers!
Mark

-----Original Message-----
From: Stacy Weng [mailto:[EMAIL PROTECTED]]
Sent: Friday, March 01, 2002 2:12 PM

I have a parent class called Component, and several child classes extending
from it.   All the common get/set methods are defined in Component.  So,
after each child is getting created from addObjectCreate() method, I call
addSetProperties() method to initialize their values (values are from the
xml file), however, digester can't find the set methods from the child
class, cause they're defined in the parent class (Component).  The temporary
solution I had was defining those set methods in the child classes, and have
them call the super methods.  But that seems to defeat the whole purpose of
inheritance.  Here's an example with the problem:

public class Component {
    public String name = null;
    public void setName(String name) {
        this.name=name;
    }
    public void getname() {
        return this.name;
    }
}

public class ChildClass extend Component {
    //Other methods that differ from parent class
}

for the digester rules:

digester.addObjectCreate("ChildClassPattern", "some.package.ChildClass");
digester.addSetProperties("ChildClassPattern");

so, as it gets to addSetProperties(), it doesn't see any of the get/set
methods in ChildClass, and yet, it doesn't know to look its parent class,
Component.

I hope I'm able to get my problem across.  Thanks again for taking the time
to respond.

--Stacy



----- Original Message ----- 
  From: Fernando Esteban Barril Otero 
  To: Struts Users Mailing List 
  Sent: Friday, March 01, 2002 1:48 PM
  Subject: Re: Digester and inheritance


  I'm using digester and inheritance without problems. What kind
  of exception are you getting?

  Fernando

  ----- Original Message -----
  From: "Stacy Weng" <[EMAIL PROTECTED]>
  To: "Struts Users Mailing List" <[EMAIL PROTECTED]>
  Sent: Friday, March 01, 2002 1:20 PM
  Subject: Digester and inheritance


  Has anyone encountered problems with inheritance using Digester?  It seems
  to me that the addSetProperties() does not when its object is inherited
from
  a parent class...hence it assumes the get/set methods aren't defined, when
  they are actually defined in its parent class.  I've looked into the
source,
  and it seems that the getMethod call that digester uses does not handle
  parent methods.  Is there a patch out there for inheritance with digester?

  Once again, thanks again in advance for any input.  It is greatly
  appreciated.  =)

  --Stacy



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