"Patrick E. Whitesell" wrote:
>
> Basically, I wanted to create a context chain where the most recently
> created context was not necessarily at the head of the chain. These
> changes allow me to do that.
Well, there are alternatives. One thing that bugs me, beyond the chance
that someone cooks up an infinite loop, is that you can't assume anymore
that a context is 'read only' when chained, which I think is important.
To illustrate, suppose you have a framework of some type that
instantiates and populates a toolbox context, something containing
common tools to be used by a request. By being able to 'add to the end'
of the chain, you can effectively modify that toolbox. Not good. Yes,
you can claim that you will remember to clean up, but I woudn't want to
bank on it as a framework.
An alternative, I think, would be a little helper Context that allows
you to add contexts in any order, and insert them anywhere, but in doing
so, doesn't assume anything about the contexts its working with.
Instead of
C -> ToolboxContext -> YourContext
have
C -> ToolboxContext
|
-> YourContext
so you get the same result w/o fear of screwing someone else up.
As a quickie example, suppose you had something like : (and forgive any
gaffes - I am winging it here with beer in hand...)
public class ContextChainer implements Context
{
private ArrayList inner = new ArrayList();
private HashMap myData = new HashMap();
/*
* add context to the vector at some position
*/
public Context addContext( int pos, Context c )
/*
* remove context from some position
*/
public Context removeContext( int pos );
/*---- Context interface --- */
public Object get( String key )
{
// check local
Object o = myData.get( key );
if ( o == null)
{
// go through the list..
Iterator i = inner.iterator();
while( i.hasNext() )
{
Context c = (Context) i.next();
o = c.get( key );
if( o != null)
return o;
}
}
return o;
}
etc...
}
Now, the advantages here is that
1) you can place your contexts in any order
2) you can remove them as well
3) you don't modify anyone elses context
4) I don't fear a loop :)
It also means that all sorts of interesting [goofy] constructs can be
made :
C -> ToolboxContext -> Toolbox2
|
-> YourContext
|
-> AnotherToolbox -> C1
|
-> C2
Comments?
geir
> Geir Magnusson Jr. wrote:
>
> > Could you provide some information what problems you were trying to
> > solve, or what you are trying to enhance? That would be great.
> >
> > geir
> >
> >
> > "Patrick E. Whitesell" wrote:
> >
> >> Hey fellas,
> >>
> >> I did some stuff to enchance the Context chaining. This is my first
> >> submission, so let me know if I'm way out of line...
> >>
> >> There are some ugly bits in here due to the fact that the innerContext
> >> is defined as a Context, not an AbstractContext. Does anyone object to
> >> making the innerContext an AbstractContext? If not, I can take the
> >> exceptions out of this code...
>
> --
> Patrick E. Whitesell
> [EMAIL PROTECTED]
--
Geir Magnusson Jr. [EMAIL PROTECTED]
System and Software Consulting
Developing for the web? See http://jakarta.apache.org/velocity/
