Re: Quick inheritence question

From:

Lew <lew@lewscanon.com>

Newsgroups:

comp.lang.java.programmer

Date:

Fri, 04 Jan 2008 20:04:47 -0500

Message-ID:

<CvydnSvNl4YtSuPanZ2dnUVZ_rSrnZ2d@comcast.com>

andymconl...@googlemail.com wrote:

public class LobBean extends SimpleTypeBean {

  public LobBean() {
  }

  public long getLob() {
    return super.getId();
  }

  public void setLob(long lob) {
    super.setId(lob);
  }

}

Is this considered bad practice or is this what I should be doing?

lord.zoltar@gmail.com wrote:

The subclass will have an id and lob.

True - the public parent methods publish a view of the 'id' as an alias for 'lob'.

What you could do: Create an abstract class "AbstractSimpleTypeBean"
that implements everything EXCEPT the id and lob. Then have subclasses
that implement id and lob as appropriate.

Or just use a 'SimpleBean' where 'id' just happens to function as a 'lob',
talks to 'lob' columns of the data store, fills in 'lob' UI fields, and just
isn't named 'lob'.

Or just write another bean that is structurally identical with different field
names.

Inheritance isn't really about refactoring for the sake of refactoring. It's
to capture a modeled "is-a" relationship. If your 'LobBean' /is-a/
'SimpleBean' then inheritance is exactly right.

In this case it partly works - LobBean puts a facade on its parent that lets
it show an 'id' as if it were a 'lob'. You don't actually need the 'super'
decorations to resolve the calls since they're public. You still have that
'id' attribute though, and that doesn't match your logical model. So that
breaks /is-a/.

--
Lew