Table of Contents

• Using the XPath View for testing and evaluating XPath expressions
• Simple Saving, Loading and Organization of XPath Expressions
• Changing Color- and Font-settings
• Customizing TAB-completion

Using the XPath View for testing and evaluating XPath expressions

• The XPath-View
• Testing XPath Expressions with live-evaluation
• Dealing with Namespaces
• Time-out and offline evaluation
• Using TAB-completion

XPath-View

If the Plugin is installed, you should find a view named XPath-View offered under Window > Show View > Other... in the category XPath-Developer.

The view looks as displayed in the screenshot below.

The XPath-View can operate in real-time or on-demand-mode. To evaluate the XPath-Expression as you change either the expression or the input you need to perform the following steps:

• Check the box 'Live-evaluation'
• Open an xml-file to be used as input. Note that XPath-Developer tries to do a good job in using whatever editor you may have associated with xml-files. However, due to the Eclipse-architecture and the large number of editor-plugins out there, XPath-Developer needs to assume something. XPath-Developer currently handles editors which adapt org.eclipse.ui.texteditor.ITextEditor. This is true (among hopefully others) for the standard text-editor and the xml- and schema-editors delivered with WTP.
• With the xml-input file open in the active editor, click 'Attach' in the XPath-View

Once the view is attached to an editor, the XPath-Expression typed in the corresponding field is evaluated on any change of the expression, the output-type, or the editor-contents. When you change the active editor or activate a view different from the XPath-View, the XPath-View automatically detaches from the editor in order not to slow the usual handling in Eclipse.

Should you want to manually suppress the evaluation of the XPath-expression without changing the active editor, click 'Detach' or untick the 'Live-evaluation'-Flag.

Below is a screenshot of a situation where some of the XML in the active editor is matched by the XPath-expression in the view. The result is evaluated as Nodelist (see the active radiobutton to the left of the result-area) and is displayed in the result-textarea.

Note that the formatting of the output is done through the Xalan-XSLT-Transformer and the formatting will typically not be identical with the formatting of the input.

If the input document declares namespaces, these are also needed in the namespace-context of the XPath-expression.

The plugin offers automatic evaluation and inclusion as well as manual control over the namespace-context. Note however that the plugin only allows a global context for the complete expression.

All namespace-settings are controled in the "Namespace-Context settings" section at the bottom of the view. If you click on the name, the section unfolds as shown in the screenshot below.

Once an expression is evaluated (online or offline), by default the plugin infers the namespace-context entries from the attributes to the first element of the input. For example, if the element is

	<?xml version='1.0'?>
	<xs:schema xmlns:hfp="http://www.w3.org/2001/XMLSchema-hasFacetAndProperty"
	           xmlns:xs="http://www.w3.org/2001/XMLSchema" blockDefault="#all"
	           elementFormDefault="qualified" xml:lang="en"
	           targetNamespace="http://www.w3.org/2001/XMLSchema"
	           version="Id: datatypes.xsd,v 1.4 2004/05/29 10:26:33 ht Exp ">
	...
	</xs:schema>
		

the plugin will pick up two context-entries as displayed below.

In case you want to experiment with the namespace-context or the plugin does not pick up the correct entries, you can turn off automatic context-setting by un-ticking "Infer from source". If this is done, you may use the button "Add Namespace-Mapping..." to add mappings. Furthermore, on double-clicking an existing entry in the table a dialog as displayed below will open, allowing you to change or delete the entry.

Since evaluation of expressions against large files may take some time and you may not be interested in real-time evaluation, the evaluation of the XPath-expression can be done offline by unsetting the mark at 'Live-evaluation' and using the 'Evaluate'-button if evaluation is in order.

The evaluation of the expression takes place in a separate thread and may be cancelled by the user or is automatically cancelled if it takes too long. The dialog for cancelling the evaluation appears with a small delay so that you will not notice it during fast live-evaluation.

The time-out behaviour is configurable from the preference page available under 'Window > Preferences...' in the category 'XPath-Developer'. The preference page is displayed with the default settings in the screenshot below.

As in several specialized editors within Eclipse, you can use TAB-completion for XPath-expressions in the XPath-View. To get a list of proposals for completion of the current expression, hit 'Ctrl+Space' while editing in the area for expressions. An assistant will open as displayed in the below screenshot. Scrolling through the suggestions also updates the hint on the left side of the proposal. When you select a proposal, XPath-Developer will try to work out whether the already typed in characters should be part of an expression or not.

The XPath-View tries to do a good job in guessing what you may want from TAB-completion. To this end, the rules are roughly as follows:

• Offer all completions which are not definitely illegal. Thus for example, you will not be offered '[]' (for a predicate) at the beginning of the expression - but almost anything else.
• Try to guess the intentions of the user in cases where things are pretty clear. Offer things starting with the most likely ones. They are the exceptions, but there are cases where it is clear what the user is after. Thus, the input 'conta' is very likely part of 'contains()'. This will be the first offer.
• In case there are several potential completions even within the rules, offer the ones with the shortest 'missing part' first. Thus, if you start with 'co' and ask for completion, you will be offered 'count()', 'concat()', ... before 'contains()'. If you keep typing and the next characters typed are a 'n' and a 't', you will notice how the order of proposals changes.