Package com.saxonica.ee.stream.adjunct

Class FilterExpressionAdjunct

java.lang.Object
com.saxonica.ee.stream.adjunct.StreamingAdjunct
com.saxonica.ee.stream.adjunct.TransmissionAdjunct
com.saxonica.ee.stream.adjunct.FilteringAdjunct
com.saxonica.ee.stream.adjunct.FilterExpressionAdjunct
All Implemented Interfaces:
FeedMaker
public class FilterExpressionAdjunct extends FilteringAdjunct
Generate streaming code for a filter expression (when not part of a Watch).

  • Constructor Details

    • FilterExpressionAdjunct

      public FilterExpressionAdjunct()

  • Method Details

    • setExpression

      public void setExpression(Expression expression)
      Set the expression being processed by this StreamingAdjunct
      Overrides:
      setExpression in class StreamingAdjunct
      Parameters:
      expression - the expression being processed

    • computeStreamability

      public PostureAndSweep computeStreamability(ContextItemStaticInfoEE contextInfo, List<String> reasons)
      Description copied from class: StreamingAdjunct
      Compute the posture and sweep of this expression as defined in the W3C streamability specifications. This must be implemented in all subclasses that don't use the general streamability rules. The implementation should have the side-effect of computing the streamability of all subexpressions, recursively.
      Overrides:
      computeStreamability in class StreamingAdjunct
      Parameters:
      contextInfo - Information about the context item type and posture
      reasons - the caller may supply a list, in which case the implementation may add to this; the contents are human-readable messages explaining why the expression is not streamable.
      Returns:
      the posture and sweep of the expression

    • toStreamingPattern

      public Pattern toStreamingPattern(Configuration config)
      Convert this expression to a streaming pattern (a pattern used internally to match nodes during push processing of an event stream)
      Overrides:
      toStreamingPattern in class StreamingAdjunct
      Parameters:
      config - the Saxon configuration
      Returns:
      the equivalent pattern if conversion succeeds; otherwise null

    • makeFilter

      public FilteringFeed.Filter makeFilter(XPathContext context, ItemFeed out)
      Make a filter for the event stream
      Specified by:
      makeFilter in class FilteringAdjunct
      Parameters:
      context - the XPath dynamic context
      out - the next filter in the pipeline
      Returns:
      a filter that can be added to the event stream

    • getFeedMaker

      public FeedMaker getFeedMaker(int arg) throws XPathException
      Description copied from class: StreamingAdjunct
      Get a FeedMaker, a factory class that creates a Feed to evaluate this expression in streaming mode. In many cases the StreamingAdjunct is itself a FeedMaker, in which case it returns itself. But where an expression has several operands, it will typically create different feeds depending on which argument is the streamed input, and in such cases the individual StreamingAdjunct makes the decision which feed to use, by returning an appropriate FeedMaker.
      Overrides:
      getFeedMaker in class StreamingAdjunct
      Parameters:
      arg - identifies the argument with respect to which the expression is to be inverted: usually 0 to indicate the first argument is the value that is streamed. Argument numbering is the same as the sequence of arguments/operands returned by the method Expression.operands()
      Returns:
      a FeedMaker to evaluate the expression, or null if it is not streamable with respect to the specificed argument.
      Throws:
      XPathException - in the event of a failure