Package com.luciad.format.aixm51.xml

Class TLcdAIXM51XPathFactory

java.lang.Object
javax.xml.xpath.XPathFactory
com.luciad.format.xml.xpath.TLcdXMLXPathFactory
com.luciad.format.aixm51.xml.TLcdAIXM51XPathFactory
public class TLcdAIXM51XPathFactory extends TLcdXMLXPathFactory

A factory for XPath objects that are applicable to AIXM 5.1 domain objects like TLcdAIXM51AbstractAIXMFeature and TLcdAIXM51AbstractAIXMTimeslice.

XPath requires namespaces to be used in the expressions. The namespaces that can be used in expressions for this factory are listed below. XPath expressions containing elements that belong to other namespaces, or that do not use the correct prefixes as specified below, will not work. If you want to support other namespaces, it is possible to construct your own XPathExpression using the standard Java API.

The following namespaces can be used:

  • aixm51: for elements of the AIXM 5.1 namespace,
  • gml: for elements of the GML 3.2 namespace,
  • message: for elements of the AIXM 5.1 Basic Message namespace,
  • event: for elements of the AIXM 5.1 DNOTAM event namespace,
  • xlink: for elements of the XLink namespace.
  • lcd: for custom functions defined by this factory,

This factory also provides the following custom functions:

  • Node lcd:getLinkedObject( Node ) This function returns the object that is linked to the given node. This assumes that the Node contains an XLink and that the XLink has been resolved; it will not try to resolve the XLink itself.
  • Node lcd:getLinkedTimeSlice( Node ) This function works the same as getLinkedObject, but it returns a timeslice of the linked feature instead of the feature itself. It uses the time slice provider that is passed in the constructor to retrieve the time slice, or the default time slice provider of the feature in case a time slice provider is not set on this XPath factory.
  • String lcd:join-string( NodeSet nodes, String separator) This function takes a node set as its first argument and a separator as an optional second argument. It concatenates the string values of the nodes in the node set, and separates them using the separator String. It is actually a replacement for the standard XPath function join-string which is currently not supported by the underlying XPath resolver.

Examples of XPath expressions for referencing properties in an AIXM 5.1 feature object:

  • The name of an AirportHeliport: /aixm51:AirportHeliport/aixm51:timeSlice/aixm51:AirportHeliportTimeSlice/aixm51:name
  • The surface composition of a Runway: /aixm51:Runway/aixm51:timeSlice/aixm51:RunwayTimeSlice/aixm51:surfaceProperties/aixm51:SurfaceCharacteristics/aixm51:composition
  • The unit of measure of the length of a Runway: /aixm51:Runway/aixm51:timeSlice/aixm51:RunwayTimeSlice/aixm51:length/@uom
  • The operational status of a Navaid: /aixm51:Navaid/aixm51:timeSlice/aixm51:NavaidTimeSlice/aixm51:operationalStatus
  • The GML identifier of a TaxiwayElement: /aixm51:TaxiwayElement/gml:identifier

These examples use absolute location paths to refer to a property, starting from the feature element itself. XPath also supports the use of abbreviated relative location paths, to reduce the number of steps in the expression. For example, the example expression to reference the name of an AirportHeliport could be rewritten in the following ways:

  • //aixm51:timeSlice/aixm51:AirportHeliportTimeSlice/aixm51:name
  • //aixm51:AirportHeliportTimeSlice/aixm51:name
  • //aixm51:name

If multiple nodes correspond to an XPath expression, the first occurrence is selected. By using a predicate, a number can be specified to indicate which node is to be selected. For example, if a Navaid has two timeslices, the following expression can be used to reference the interpretation of the second timeslice:

  • /aixm51:Navaid/aixm51:timeSlice[2]/aixm51:NavaidTimeSlice/aixm51:interpretation
Since:
10.0
See Also: