The Java EE 5 Tutorial (PDF) - Oracle Software Downloads

Encapsulating Reusable Content UsingTag Files
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Evaluating Fragments Passed toTag Files
When a tag file is executed, the web container passes it two types of fragments: fragment
attributes and the tag body. Recall from the discussion of fragment attributes that fragments are
evaluated by the tag handler as opposed to the web container. Within a tag file, you use the
jsp:invoke element to evaluate a fragment attribute and use the jsp:doBody element to
evaluate a tag file body.
The result of evaluating either type of fragment is sent to the response or is stored in an EL
variable for later manipulation. To store the result of evaluating a fragment to an EL variable,
you specify the var or varReader attribute. If var is specified, the container stores the result in
an EL variable of type String with the name specified by var.IfvarReader is specified, the
container stores the result in an EL variable of type java.io.Reader, with the name specified by
varReader. The Reader object can then be passed to a custom tag for further processing. A
translation error occurs if both var and varReader are specified.
An optional scope attribute indicates the scope of the resulting variable. The possible values are
page (default), request, session,orapplication. A translation error occurs if you use this
attribute without specifying the var or varReader attribute.
The Java EE 5Tutorial • June 2010