<oXygen/> XML Editor User Guide

Working with the XSLT Debugger

The following topics are present about how to follow XSLT processing and detect errors in your stylesheets:

Steps in a typical debug process

To debug a stylesheet follow the procedure:

  1. Open the source XML document, eventually also open the XSLT stylesheet.

  2. If you are in the Editor perspective switch to the Debugger perspective with one of the actions:

    • Perspective->Debugger or the toolbar button Debugger

    • Document->XML Document->Debug scenario or the toolbar button Debug scenario

  3. Select the source XML document in the XML source selector of the Control toolbar

  4. Select the XSL document in the XSL stylesheet selector of the Control toolbar

  5. Set XSLT parameters from the button available on the Control toolbar

  6. Set one or more breakpoints.

  7. Step through the stylesheet using the buttons available on the Control toolbar: Step into, Step over, Step out, Run, Run to cursor, Run to end, Pause, Stop

  8. Examine the information in the Information Views to find the bug in the transformation process.

Using breakpoints

The <oXygen/> XSLT debugger allows you to interrupt XSLT processing to gather information about variables and processor execution at particular points.

Inserting breakpoints

To insert a breakpoint:

  1. In the XML source document or the XSLT stylesheet that you want to set a breakpoint, place your cursor on the line where you want the breakpoint to be.

  2. Select Edit-> Breakpoints->Create or directly click with the mouse the left side stripe of the editor window on the line where you want the breakpoint to be.

Removing breakpoints

To remove a breakpoint:

  • Click with the mouse the left side stripe of the editor window on the line with the breakpoint or select Edit-> Breakpoints->Remove all

Viewing processing information

Detailed informations about the debugger status are provided using the information views.

Context node view

The context node is a source node corresponding to the XSL expression being evaluated. It is also called the context of execution. The context node implicitly changes as the processor hits various steps (at the point where XPath expressions are evaluated). This node has the same value as evaluating '.' (dot) XPath expression on XPath watch view.

Figure 7.3. The Context node view

The Context node view

Table 7.1. Context node details

Column Description
Name Name of source (XML) node.
Attributes/Value Attributes or value of the XML node. If attributes exist, they are shown under the form of attributeName ="attributeValue", otherwise the text content of the node is shown.

XPath watch view

Shows XPath expressions to be evaluated during debugging. Expressions are evaluated dynamically as the processor changes its source context.

Figure 7.4. The XPath watch view

The XPath watch view

Table 7.2. XWatch details

Column Description
Expression XPath expression to be evaluated (should be XPath 1.0 or 2.0 compliant).
Value Result of XPath expression evaluation. Value has a type (see Possible Values in the section Variables view). For Node Set results the number of nodes in the set is shown in parenthesis.
[Important]Remarks
  • Expressions reffering to variables names are not evaluated. In case of an XPath error, you get an Error line.

  • The expression list is not deleted at the end of transformation (it is preserved during sessions).

  • To insert a new expression click the last line on the expression column and enter it. Press enter on cell to add and evaluate.

  • To delete an expression click on its Expression column and delete its content. Press enter on cell to commit changes.

  • If the expression result type is a Node Set you can click on it (Value column) and you will see on the right side its value. (see Node set view).

Breakpoints view

Lists all breakpoints set on opened documents. Once you set a breakpoint it is automatically added in this list. Breakpoints can be set on both XML and XSL documents.

Figure 7.5. The Breakpoints view

The Breakpoints view

Table 7.3. Breakpoints details

Column Description
Resource Resource file where the breakpoint is set. Entire path of resource file is available as tooltip.
Line Line number inside resource where the breakpoint is set.
[Important]Valid Breakpoint
  • Not all set breakpoints are valid. For example if the breakpoint is set on one empty or commented line or the line is not reached by the processor (no template to match it, line containing only an end tag), that breakpoint is invalid.

  • The contextual menu on table has the Remove and Go to options.

  • Clicking a record highlights the breakpoint line into the document.

Messages view

<xsl:message> instructions are one way to signal special situations encountered during transformation as well as a raw way of doing the debugging. This view shows all <xsl:message> calls executed by the XSLT processor during transformation.

Figure 7.6. The Messages view

The Messages view

Table 7.4. Messages details

Column Description
Message Message content.
Terminate Signals if processor will terminate the transformation or not once it encounters the message (true/false respectively)
Resource Resource file where <xsl:message> instruction is defined. The complete path of the resource is available as tooltip.
[Important]Remarks
  • Clicking a record from the table highlights the <xsl:message> declaration line.

  • Message table values can be sorted by clicking the corresponding column header (ascending, descending, no sort)

Stack view

Shows the current execution stack of both source and style nodes. During transformation two stacks are managed: one of source nodes being processed and the other for stylesheet nodes being processed. <oXygen/> shows both node types into one common stack. The source (XML) nodes are preceded by a red color icon while stylesheet nodes are preceded by a green color icon. The advantage of this approach is that you can always see the source scope on which a stylesheet instruction is executed (the last red color node on the stack). The stack is oriented upside down.

Figure 7.7. The Stack view

The Stack view

Table 7.5. Stack details

Column Description
# Order number, represents the depth of the node (0 is the stack base).
XML/XSL Node Node from source or stylesheet document currently being processed. One particular stack node is the document root, noted as #document.
Attributes Attributes of the node (list of id="value" pairs).
Resource Resource file where the node is located. Entire path is available as tooltip.
[Important]Remarks
  • Clicking a record from the stack highlights that node's location inside resource.

  • Using Saxon, the stylesheet elements are qualified with XSL proxy, while on Xalan you only see their names. (example <xsl:template> on Saxon and template on Xalan).

  • Only Saxon processor shows element attributes.

  • Xalan processor shows the "built-in" rules.

Trace history view

Usually the XSLT processors signal the following events during transformation:

  • entering a source (XML) node.

  • leaving a source (XML) node.

  • entering a stylesheet (XSL) node.

  • leaving a stylesheet (XSL) node.

The trace history catches all these events, so you can see how the process evolved. The red icon lines denote source nodes while the green icon lines denote stylesheet nodes.

It is possible to save the element trace in a structured XML document. It is available on the context menu of the view. In this way you have the possiblity to compare the trace results from different debug sessions.

Figure 7.8. The Trace History View

The Trace History View

Table 7.6. Trace History details

Column Description
Depth Starts from 0 and represents the level of overlapping for that node. This is similar with the # order number from stack at the moment the node was processed.
XML/XSL Node Represents the node from the processed source or stylesheet document. One particular node is the document root, noted as #document. Every node has an arrow in front of it representing what action was performed on it (entering or leaving).
Attributes Attributes of the node (list of id="value" pairs).
Resource Resource file where the node is located. Complete path to resource file is provided as tooltip.
[Important]Remarks
  • Clicking a record highlights that node's location inside the resource.

  • Only Saxon processor shows element attributes.

  • Xalan processor shows the "built-in" rules.

Templates view

The <xsl:template> is the basic element for stylesheets transformation. This view shows all <xsl:template> instructions used by the transformation. By seeing the number of hits for each of the templates you get an idea of the stylesheet coverage by template rules with respect to the input source.

Figure 7.9. The Templates view

The Templates view

Table 7.7. Templates details

Column Description
Match Match attribute of the <xsl:template>.
Hits Number of hits for the <xsl:template>. Shows how many times the XSLT processor used this particular template.
Priority Template priority as established by XSLT processor.
Mode Mode attribute of the <xsl:template>.
Name Name attribute of the <xsl:template>.
Resource Resource file where template is located. Complete path of resource file is available as tooltip.
[Important]Remarks
  • Clicking a record highlights that template definition inside resource.

  • Saxon only shows the applied templates having at least one hit from the processor. Xalan shows all defined templates, with or without hits.

  • Template table values can be sorted by clicking the corresponding column header (ascending, descending, no sort)

  • Xalan shows the "built-in" rules.

Node set view

This view is always used in relation with Variables view and XPath watch view and shows a nodeset value. Once you click a variable having as value a nodeset or tree fragment or an XPath expression evaluated to a nodeset in the above views the node set view gets updated with the respective value.

Figure 7.10. The Node Set view

The Node Set view

Table 7.8. Node set details

Column Description
Name Name of source (XML) node.
Attributes/Value Attributes or text content (Value) of the XML node. If attributes exist, these are shown under the form of attributeName ="attributeValue", otherwise the text content of the node is shown.
[Important]Remarks
  • In case of longer values for Value/Attributes column content, the interface shows three suspension points (...) at the end. A more detailed value is available as tooltip.

  • Clicking a record highlights the location of that node into the source or stylesheet view.

Variables view

During transformation variables and parameters play an important role.

<oXygen/> uses the following icons to differentiate variables/parameters:

  • Global variable.

  • Local variable.

  • Global parameter.

  • Local parameter.

The values types of a variable are marked by icons explained below:

Possible Values

  • Boolean.

  • String.

  • Numeric.

  • Node set.

  • Tree fragment.

  • Date. (XSLT 2.0 only)

  • Object.

  • Any.

Figure 7.11. The Variables view

The Variables view

Table 7.9. Variables details

Column Description
Name Name of the variable/parameter.
Value Current value for the variable/parameter.
[Important]Remarks
  • Clicking a record highlights the variable definition line.

  • Variable values could differ depending on the transformation engine used or stylesheet version set.

  • If the value of the variable is a node-set or a tree-fragment, clicking on it causes the Node set view to be shown with corresponding set of values.

  • Variable table values can be sorted by clicking the corresponding column header (ascending, descending, no sort)

Determining what template generated particular output

In order to quickly spot the templates with problems it is important to know what XSL template in the XSL stylesheet and what element in the source XML document generated a specified area in the output. Some of the debugging capabilities, for example "Step in" can be used for this purpose. Using "Step in" you can see how output is generated and link it with the style element being executed in the current source context. However, this can become difficult on complex stylesheets that generates a large output.

Output to source mapping is a powerful feature that makes this output to source mapping persistent that is you can click on the text from the Output document view and the editor will select the XML source context and the XSL element that generated the text.

Figure 7.12. Output to Source Mapping

Output to Source Mapping
  1. If you are in the Editor perspective switch to the Debugger perspective with one of the actions:

    • Perspective->Debugger or the toolbar button Debugger

    • Document->XML Document->Debug scenario or the toolbar button Debug scenario

  2. Select the source XML document in the XML source selector of the Control toolbar

  3. Select the XSL document in the XSL stylesheet selector of the Control toolbar

  4. Select the XSLT engine in the XSLT engine selector of the Control toolbar

  5. Set XSLT parameters from the button available on the Control toolbar

  6. Apply the stylesheet using the button Run to end available on the Control toolbar:

  7. Inspect the mapping by clicking a section of the output from the Text view tab or from the XHTML view tab of the Output document view to have the stylesheet element and the source context highlighted.

    Figure 7.13. XHTML Output Mapping

    XHTML Output Mapping