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<?xml version="1.0" standalone="no"?>
<!DOCTYPE s1 SYSTEM "../../style/dtd/document.dtd">
<!--
* Copyright 2001-2004 The Apache Software Foundation.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
-->
<!-- $Id: xsl_comment_design.xml 337884 2004-02-17 19:29:35Z minchau $ -->
<s1 title="<xsl:comment> / <xsl:message>">
<ul>
<li><link anchor="functionality">Functionality</link></li>
<li><link anchor="implementation">Implementation</link></li>
</ul>
<anchor name="functionality"/>
<s2 title="Functionality">
<p>The <code><xsl:comment></code> element is used to insert XML comments
into the result document. The comment is inserted as follows in the XSL
stylesheet:</p>
<source> <element>
<xsl:comment>This is a comment!</xsl:comment>
</element></source>
<p>and it will be output in the result document as follows:</p>
<source> <element>
<!-- This is a comment! -->
</element></source>
<p>The <code><xsl:message></code> element is used to send messages to
who/whatever is performing the transformation. The message can be displayed
in a terminal, a dialog box, etc. The <code><xsl:message></code> element
is used in the same way as the <code><xsl:comment></code> element,
however the message is <em>not</em> output in the result document.</p>
<p>The <code><xsl:message></code> element has an attribute
<code>"terminate"</code> which can be used to terminate the transformation at any
given stage. This is useful when using message to give information about
illegal values in the input document.</p>
</s2><anchor name="implementation"/>
<s2 title="Implementation">
<p>The output handler class has a method for outputting comments in the
output document and messages to the operator. The code compiled for a
comment gathers all text that goes into the comment in a StringValueHandler
object, retrieves the full text string from this handler, and then finally
sends it to the output handler. Similarly the code compiled for a message
will simply send the message to the output handler in use.</p>
<p>Messages will be output to the terminal (stdout) when a transformation
is run in a terminal. The message will be output before the beginning of the
output document. Messages will be shown in a dialog box if a transformation
is run in an applet.</p>
<p><code><xsl:message></code> elements that use the <code>"terminate"</code>
attribute to abort transformations cause an exception to be thrown. A
RuntimeException is used for this, and the exception text is:</p>
<p><code>Termination forced by an xsl:message instruction</code></p>
</s2>
</s1>
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