org.apache.commons.chain
Interface Filter
- All Superinterfaces:
- Command
- All Known Implementing Classes:
- DispatchLookupCommand, LookupCommand, PathInfoMapper, RequestParameterMapper, ServletPathMapper
public interface Filter
- extends Command
A Filter
is a specialized Command
that also expects
the Chain
that is executing it to call the
postprocess()
method if it called the execute()
method. This promise must be fulfilled in spite of any possible
exceptions thrown by the execute()
method of this
Command
, or any subsequent Command
whose
execute()
method was called. The owning Chain
must call the postprocess()
method of each Filter
in a Chain
in reverse order of the invocation of their
execute()
methods.
The most common use case for a Filter
, as opposed to a
Command
, is where potentially expensive resources must be acquired
and held until the processing of a particular request has been completed,
even if execution is delegated to a subsequent Command
via the
execute()
returning false
. A Filter
can reliably release such resources in the postprocess()
method, which is guaranteed to be called by the owning Chain
.
- Version:
- $Revision: 480477 $ $Date: 2006-11-29 08:34:52 +0000 (Wed, 29 Nov 2006) $
- Author:
- Craig R. McClanahan
Method Summary |
boolean |
postprocess(Context context,
Exception exception)
Execute any cleanup activities, such as releasing resources that
were acquired during the execute() method of this
Filter instance. |
Methods inherited from interface org.apache.commons.chain.Command |
execute |
postprocess
boolean postprocess(Context context,
Exception exception)
Execute any cleanup activities, such as releasing resources that
were acquired during the execute()
method of this
Filter
instance.
- Parameters:
context
- The Context
to be processed by this
Filter
exception
- The Exception
(if any) that was thrown
by the last Command
that was executed; otherwise
null
- Returns:
- If a non-null
exception
was "handled" by this
method (and therefore need not be rethrown), return true
;
otherwise return false
- Throws:
IllegalArgumentException
- if context
is null
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