xsl:try

In conjunction with xsl:catch, the xsl:try instruction allows recovery from dynamic errors occurring within the expression it wraps.

Category: instruction
Content: ( sequence-constructor , xsl:catch , ( xsl:catch | xsl:fallback )* )
Permitted parent elements: any XSLT element whose content model is sequence-constructor; any literal result element

Attributes

select?

expression

The expression to be evaluated by the instruction may be defined either by a select attribute, or by an enclosed sequence constructor.

rollback-output?

boolean

The value no is used to relax the requirement to recover result trees when failures occur in the course of evaluating the xsl:try instruction. The default is yes. (This attribute had no effect prior to Saxon 9.9.)

Saxon availability

Available in XSLT 3.0. From Saxon 9.8, available in all editions. Implemented in Saxon-PE and Saxon-EE since Saxon 9.6. Available for all platforms.

Notes on the Saxon implementation

Saxon 9.9 no longer ignores the value of the rollback-output attribute. If set to "no", when the instruction is evaluated in "push" mode, the output of xsl:try is not buffered, but is written directly to the result destination. If a dynamic error occurs, the relevant xsl:catch is effective only if no output has yet been written to that destination.

Details

It is possible to have more than one xsl:catch within an xsl:try; the first one that matches the error is used.

Within the xsl:catch, a number of variables are available in the namespace http://www.w3.org/2005/xqt-errors:

The error can be re-thrown by using the error() function.

Examples

Example 1

The following example shows how to recover from an error in evaluating an XPath expression (in this case, divide-by-zero):

<xsl:try select="salary div length-of-service"> <xsl:catch errors="err:FAOR0001" select="()"/> </xsl:try>

Example 2

The following example shows how to recover from an error in evaluating a sequence of XSLT instructions (in this case, a validation error):

<xsl:try> <xsl:copy-of select="$result" validation="strict"/> <xsl:catch> <xsl:message>Warning: validation of result document failed: Error code: <xsl:value-of select="$err:code"/> Reason: <xsl:value-of select="$err:description"/> </xsl:message> <xsl:sequence select="$result"/> </xsl:catch> </xsl:try>

Links to W3C specifications

XSLT 3.0 Specification

See also

xsl:catch

xsl:fallback

error()