Ryan Shaw wrote:
> Paulo wrote:
>
> ||| /** Releases all not-yet-released components. */
> ||| public void releaseAll();
>
> actually, isn't this A Bad Thing?
>
> if something like releaseAll() were public, any
> Composable could release all the Components being
> managed.
That is why releaseAll should have a Token. That Token scopes the components
that are released.
Granted, I would rather have the release mechanism on the Token object,
that way there is no chance of a BadTokenException to be thrown, or possible
resource leakage by managing several tokens.
Granted, the Token approach *can* be applied regardless of what the manager
interface is (as long as the manager has a release(Object) method). Example:
public interface ServiceManager
{
Object lookup(Object key); // can be Query or String based role
boolean hasResource(Object key); // can be Query or String based role
void release(Object resource);
}
public final class Token
{
private final ServiceManager m_manager;
private final Buffer m_resources;
public Token( ServiceManager manager )
{
m_manager = manager;
m_resources = new VariableSizedBuffer();
}
public void register(Object resource)
{
m_resources.add( resource );
}
public void releaseAll()
{
int size = m_resources.size();
for (int i = 0; i < size; i++)
{
m_manager.release( m_resources.remove() );
}
}
}
The usage would be something like this:
class Example extends Servicable
{
ServiceManager m_manager;
Token m_token;
void service( ServiceManager manager )
{
m_manager = manager;
m_token = new Token( manager );
}
void criticalSection()
{
Parser parser = (Parser) m_manager.lookup(Parser.ROLE);
m_token.register( parser );
Transformer transformer = (Transformer) m_manager.lookup(Transformer.ROLE);
m_token.register( transformer );
// do the critical stuff
m_token.releaseAll();
}
}
As you can see, we can still have a Token approach--regardless of what the
interface gives us. While I would rather have the Manager initialize the
Token with the ServiceManager and the associated services (only exposing a
public releaseAll() method)--it can be done nonetheless.
--
"They that give up essential liberty to obtain a little temporary safety
deserve neither liberty nor safety."
- Benjamin Franklin
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