THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
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XWork-specific
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language
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features
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The
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biggest
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addition
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that
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XWork
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provides
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on
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top
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of
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OGNL
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is
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the
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support
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for
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the
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ValueStack.
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While
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OGNL
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operates
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under
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the
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assumption
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there
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is
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only
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one
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"root",
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XWork's
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ValueStack
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concept
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requires
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there
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be
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many
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"roots".
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For
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example,
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suppose
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we
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are
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using
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standard
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OGNL
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(not
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using
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XWork)
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and
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there
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are
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two
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objects
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in
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the
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OgnlContext
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map:
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"foo"
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->
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foo
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and
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"bar"
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->
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bar
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and
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that
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the
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foo
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object
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is
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also
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configured
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to
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be
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the
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single
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root
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object.
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The
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following
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code
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illustrates
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how
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OGNL
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deals
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with
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these
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three
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situations:
| Code Block | ||||
|---|---|---|---|---|
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{code:none} #foo.blah // returns foo.getBlah() #bar.blah // returns bar.getBlah() blah // returns foo.getBlah() because foo is the root {code} |
What
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this
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means
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is
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that
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OGNL
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allows
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many
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objects
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in
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the
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context,
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but
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unless
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the
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object
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you
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are
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trying
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to
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access
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is
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the
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root,
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it
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must
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be
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prepended
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with
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a
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namespaces
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such
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as
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@bar.
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Now
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let's
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talk
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about
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how
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XWork
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is
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a
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little
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different...
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In
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XWork,
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the
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entire
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ValueStack
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is
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the
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root
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object
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in
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the
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context.
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But
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rather
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than
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having
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your
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expressions
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get
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the
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object
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you
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want
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from
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the
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stack
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and
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then
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get
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properties
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from
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that
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(ie:
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peek().blah),
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XWork
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has
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a
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special
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OGNL
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PropertyAccessor
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that
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will
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automatically
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look
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at
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the
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all
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entries
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in
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the
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stack
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(from
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the
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top
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down)
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until
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it
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finds
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an
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object
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with
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the
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property
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you
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are
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looking
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for.
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For
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example,
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suppose
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the
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stack
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contains
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two
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objects:
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Animal
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and
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Person.
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Both
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objects
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have
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a
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"name"
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property,
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Animal
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has
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a
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"species"
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property,
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and
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Person
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has
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a
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"salary"
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property.
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Animal
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is
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on
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the
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top
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of
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the
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stack,
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and
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Person
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is
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below
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it.
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The
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follow
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code
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fragments
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help
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you
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get
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an
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idea
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of
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what
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is
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going
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on
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here:
| Code Block | ||||
|---|---|---|---|---|
| ||||
{code:none} species // call to animal.getSpecies() salary // call to person.getSalary() name // call to animal.getName() because animal is on the top {code} |
In
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the
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last
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example,
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there
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was
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a
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tie
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and
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so
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the
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animal's
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name
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was
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returned.
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Usually
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this
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is
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the
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desired
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effect,
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but
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sometimes
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you
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want
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the
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property
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of
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a
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lower-level
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object.
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To
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do
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this,
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XWork
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has
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added
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support
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for
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indexes
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on
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the
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ValueStack.
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All
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you
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have
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to
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do
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is:
| Code Block | ||||
|---|---|---|---|---|
| ||||
[0 {code:none} \[0\].name // call to animal.getName() \[1\].name // call to person.getName() {code} h2. Accessing static properties OGNL supports accessing static properties as well as static methods. As the OGNL docs point out, you can explicetly call statics by doing the following: {code:none} |
| Wiki Markup |
|---|
With expression like \[0\] ... \[3\] etc. WebWork will cut the stack and still returned back a CompoundRoot object. To get the top of that particular stack cut, use [0].top |
ognl expression | description | ||
|---|---|---|---|
<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="35067b78-d191-451e-9e4f-6fab49a68cc8"><ac:plain-text-body><![CDATA[ | [0].top | would get the top of the stack cut starting from element 0 in the stack (similar to top in this case) | ]]></ac:plain-text-body></ac:structured-macro> |
<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="53d5a4ec-f024-48fb-ae7a-4452ce1640a8"><ac:plain-text-body><![CDATA[ | [1].top | would get the top of the stack cut starting from element 1 in the stack]]></ac:plain-text-body></ac:structured-macro> |
Accessing static properties
OGNL supports accessing static properties as well as static methods. As the OGNL docs point out, you can explicetly call statics by doing the following:
| Code Block | ||||
|---|---|---|---|---|
| ||||
@some.package.ClassName@FOO_PROPERTY
@some.package.ClassName@someMethod()
{code}
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However,
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XWork
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allows
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you
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to
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avoid
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having
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to
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specify
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the
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full
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package
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name
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and
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call
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static
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properties
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and
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methods
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of
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your
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action
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classes
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using
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the
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"vs"
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prefix:
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| Code Block | ||||
|---|---|---|---|---|
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<at:var at:name="vs" />FOO_PROPERTY
<at:var at:name="vs" />someMethod()
<at:var at:name="vs1" />FOO_PROPERTY
<at:var at:name="vs1" />someMethod()
<at:var at:name="vs2" />BAR_PROPERTY
<at:var at:name="vs2" />someOtherMethod()
|
"vs" stands for "value stack". The important thing to note here is that if the class name you specify is just "vs", the class for the object on the top of the stack is used. If you specify a number after the "vs" string, an object's class deeper in the stack is used instead.
Differences from the WebWork 1.x EL
| Wiki Markup |
|---|
Besides the examples and descriptions given above, there are a few major changes in the EL since WebWork 1.x. The biggest one is that properties are no longer accessed with a forward slash \(/\) but with a dot (.). Also, rather than using ".." to traverse down the stack, we now use "\[n\]" where n is some positive number. Lastly, in WebWork 1.x one could access special named objects (the request scope attributes to be exact) by using "@foo", but now special variables are accessed using "#foo". However, it is important to note that "#foo" does NOT access the request attributes. Because XWork is not built only for the web, there is no concept of "request attributes", and thus "#foo" is merely a request to another object in the OgnlContext other than the root. |
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Old Expression | New Expression |
|---|---|
foo/blah | foo.blah |
foo/someMethod() |
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foo.someMethod() |
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<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="7b145076-11ab-4a71-aeb3-9c08ee4f9d5f"><ac:plain-text-body><![CDATA[ | ../bar/blah |
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[1 |
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].bar.blah |
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]]></ac:plain-text-body></ac:structured-macro> | |||
@baz | not directly supported, but #baz is similar | ||
<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="2c8c918e-fdf4-47a2-8bed-cb9c8fe3576b"><ac:plain-text-body><![CDATA[ | . | top or [0] | ]]></ac:plain-text-body></ac:structured-macro> |
WebWork-specific named objects
name | value | ||
|---|---|---|---|
<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="a6ef318d-1587-4481-b3eb-acb6a131e179"><ac:plain-text-body><![CDATA[ | #parameters['foo'] or #parameters.foo | request parameter ['foo'] (request.getParameter()) | ]]></ac:plain-text-body></ac:structured-macro> |
<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="4b7cec65-1ad1-4cb7-83f9-b69f2c42f919"><ac:plain-text-body><![CDATA[ | #request['foo'] or #request.foo | request attribute ['foo'] (request.getAttribute()) | ]]></ac:plain-text-body></ac:structured-macro> |
<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="1bc0289b-2ad7-4e7b-9c0f-5c26dca304b7"><ac:plain-text-body><![CDATA[ | #session['foo'] or #session.foo | session attribute 'foo' | ]]></ac:plain-text-body></ac:structured-macro> |
<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="193026ec-9b8f-48a8-b96a-607120aafc7e"><ac:plain-text-body><![CDATA[ | #application['foo'] or #application.foo | ServletContext attributes 'foo' | ]]></ac:plain-text-body></ac:structured-macro> |
<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="8b6b7a66-3646-41ac-aa7e-d3940ba89c70"><ac:plain-text-body><![CDATA[ | #attr['foo'] or #attr.foo | Access to PageContext if available, otherwise searches request/session/application respectively | ]]></ac:plain-text-body></ac:structured-macro> |