Dave Ford wrote:
>
> >From within a body tag, there seems to be multiple writers for outputting
> data. What is the difference between these 3 choices:
>
> bodyContent.getEnclosingWriter().println("Hello");
> bodyContent.println("Hello");
> pageContext.getOut().println("Hello");
The BodyContent class is only used when you develop your own custom
tag handlers. An instance of this class is used to capture the
evaluation of the elements body so the tag handler (if it's a BodyTag)
can get access to it and process it.
BodyContent.getEnclosingWriter()
Returns the writer for the parent element, or the main JspWriter
for the page if the element is not nested within another JSP
action element. You use this method to get a Writer to use for
the output your tag handler generates. If your tag handler extends
BodyTagSupport, you can use getPreviousOut() as well; it has the
same result.
BodyContent.println()
This method is inherited from the Writer superclass (along with a lot
of other similar methods). It writes to the BodyContent instance itself
and is intended to be used by the generated code to capture the
content generated by the element's body so that the tag handler can
process it later. You're not supposed to use this method in your own
code.
PageContext.getOut()
This method returns the currently "active" JspWriter or BodyContent
instance. The code generated for the JSP page reassigns "out" to a
BodyContent instance when it encounters a custom action with a tag
handler that implements BodyTag. This method therefore returns the
main JspWriter if it's called from a scriptlet on the "top level"
in a JSP page and a BodyContent instance if it's called from a scriptlet
within the body of a BodyTag custom action. It's intended to be used
by the generated code, and it can also be used by scriptlets that
want to call println() etc. In general though, I recommend that you
do not use scriptlets to generate output; let the JSP container
handle that and use scriptlets only for simple conditional statements:
<% if (someCondition) { %>
This text is added to the response by the container if the
condition is true.
<% } else { %>
This is added if it's false.
<% } %>
Hans
--
Hans Bergsten [EMAIL PROTECTED]
Gefion Software http://www.gefionsoftware.com
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