The xsl:message element causes a message to be displayed. The message is the contents of the xsl:message element.

There is an optional attribute terminate with permitted values yes and no; the default is no. If the value is set to yes, processing of the stylesheet is terminated after issuing the message. This attribute may be supplied as an attribute value template.

By default the message is displayed on the standard error output stream. You can supply your own message receiver if you want it handled differently. This must be a class that implements the Receiver interface. The content of the message is in general an XML fragment. You can supply the Receiver using the -m option on the command line, or the setMessageEmitter() method of the Controller class.

The sequence of calls to this Receiver is as follows: there is a single open() call at the start of the transformation, and a single close() call at the end; and each evaluation of an xsl:message instruction starts with a startDocument() call and ends with endDocument(). The startDocument() event has a properties argument indicating whether terminate="yes" was specified, and the locationId on calls such as startElement() and characters() can be used to identify the location in the stylesheet where the message data originated (this is achieved by passing the supplied locationId in a call to getPipelineConfiguration().getLocator().getSystemId(locationId), or to getLineNumber() on the same object).

Select the class MessageWarner to have xsl:message output notified to the JAXP ErrorListener, as described in the JAXP documentation.

Saxon 9.5 implements the new feature of text value templates which is particularly useful with xsl:message. For example: <xsl:message expand-text="yes">Id: {@id} Age: {@age} Status: {@status}</xsl:message>. The attribute expand-text="yes" can appear on any ancestor element to enable the feature.