| A
Context represents the state information that is
accessed and manipulated by the execution of a
Command or a
Chain . Specialized implementations of
Context will
typically add JavaBeans properties that contain typesafe accessors
to information that is relevant to a particular use case for this
context, and/or add operations that affect the state information
that is saved in the context.
Implementations of
Context must also implement all of the
required and optional contracts of the java.util.Map
interface.
It is strongly recommended, but not required, that JavaBeans
properties added to a particular
Context implementation exhibit
Attribute-Property Transparency. In other words,
a value stored via a call to setFoo(value) should be visible
by calling get("foo"), and a value stored
via a call to put("foo", value) should be
visible by calling getFoo(). If your
Context implementation class exhibits this featue, it becomes easier to reuse the
implementation in multiple environments, without the need to cast to a
particular implementation class in order to access the property getter
and setter methods.
To protect applications from evolution of this interface, specialized
implementations of
Context should generally be created by extending
the provided base class (
org.apache.commons.chain.impl.ContextBase )
rather than directly implementing this interface.
Applications should NOT assume that
Context implementations, or the values stored in its
attributes, may be accessed from multiple threads
simultaneously unless this is explicitly documented for a particular
implementation.
author:
Craig R. McClanahan
version:
$Revision: 155403 $ $Date: 2005-02-26 12:52:46 +0000 (Sat, 26 Feb 2005) $ |