Class SimplePathInterpreter

java.lang.Object
org.apache.commons.jxpath.ri.axes.SimplePathInterpreter

public class SimplePathInterpreter extends Object
An evaluation mechanism for simple XPaths, which is much faster than the usual process. It is only used for xpaths which have no context-dependent parts, consist entirely of child::name and self::node() steps with predicates that either integer or have the form [@name = ...].
Version:
$Revision: 652845 $ $Date: 2008-05-02 12:46:46 -0500 (Fri, 02 May 2008) $
  • Field Details

    • QNAME_NAME

      private static final QName QNAME_NAME
    • PERFECT_MATCH

      private static final int PERFECT_MATCH
      See Also:
  • Constructor Details

    • SimplePathInterpreter

      public SimplePathInterpreter()
  • Method Details

    • interpretSimpleLocationPath

      public static NodePointer interpretSimpleLocationPath(EvalContext context, NodePointer root, Step[] steps)
      Interpret a simple path that starts with the given root and follows the given steps. All steps must have the axis "child::" and a name test. They can also optionally have predicates of type [@name=expression] or simply [expression] interpreted as an index.
      Parameters:
      context - evaluation context
      root - root pointer
      steps - path steps
      Returns:
      NodePointer
    • interpretSimpleExpressionPath

      public static NodePointer interpretSimpleExpressionPath(EvalContext context, NodePointer root, Expression[] predicates, Step[] steps)
      Interpret the steps of a simple expression path that starts with the given root, which is the result of evaluation of the root expression of the expression path, applies the given predicates to it and then follows the given steps. All steps must have the axis "child::" or "attribute::" and a name test. They can also optionally have predicates of type [@name=...] or simply [...] interpreted as an index.
      Parameters:
      context - evaluation context
      root - root pointer
      predicates - predicates corresponding to steps
      steps - path steps
      Returns:
      NodePointer
    • doStep

      private static NodePointer doStep(EvalContext context, NodePointer parent, Step[] steps, int currentStep)
      Recursive evaluation of a path. The general plan is: Look at the current step, find nodes that match it, iterate over those nodes and for each of them call doStep again for subsequent steps.
      Parameters:
      context - evaluation context
      parent - parent pointer
      steps - path steps
      currentStep - step number
      Returns:
      NodePointer
    • doStepNoPredicatesPropertyOwner

      private static NodePointer doStepNoPredicatesPropertyOwner(EvalContext context, PropertyOwnerPointer parentPointer, Step[] steps, int currentStep)
      We have a step that starts with a property owner (bean, map, etc) and has no predicates. The name test of the step may map to a scalar property or to a collection. If it is a collection, we should apply the tail of the path to each element until we find a match. If we don't find a perfect match, we should return the "best quality" pointer, which has the longest chain of steps mapping to existing nodes and the shortes tail of Null* pointers.
      Parameters:
      context - evaluation context
      parentPointer - property owner pointer
      steps - path steps
      currentStep - step number
      Returns:
      NodePointer
    • doStepNoPredicatesStandard

      private static NodePointer doStepNoPredicatesStandard(EvalContext context, NodePointer parentPointer, Step[] steps, int currentStep)
      A path that starts with a standard InfoSet node (e.g. DOM Node) and has no predicates. Get a child iterator and apply the tail of the path to each element until we find a match. If we don't find a perfect match, we should return the "best quality" pointer, which has the longest chain of steps mapping to existing nodes and the shortes tail of Null* pointers.
      Parameters:
      context - evaluation context
      parentPointer - parent pointer
      steps - path steps
      currentStep - step number
      Returns:
      NodePointer
    • doStepPredicatesPropertyOwner

      private static NodePointer doStepPredicatesPropertyOwner(EvalContext context, PropertyOwnerPointer parentPointer, Step[] steps, int currentStep)
      A path that starts with a property owner. The method evaluates the first predicate in a special way and then forwards to a general predicate processing method.
      Parameters:
      context - evaluation context
      parentPointer - parent pointer
      steps - path steps
      currentStep - step number
      Returns:
      NodePointer
    • createChildPointerForStep

      private static NodePointer createChildPointerForStep(PropertyOwnerPointer parentPointer, Step step)
      Create the child pointer for a given step.
      Parameters:
      parentPointer - parent pointer
      step - associated step
      Returns:
      NodePointer
    • doStepPredicatesStandard

      private static NodePointer doStepPredicatesStandard(EvalContext context, NodePointer parent, Step[] steps, int currentStep)
      A path that starts with a standard InfoSet node, e.g. a DOM Node. The method evaluates the first predicate in a special way and then forwards to a general predicate processing method.
      Parameters:
      context - evaluation context
      parent - parent pointer
      steps - path steps
      currentStep - step number
      Returns:
      NodePointer
    • doPredicate

      private static NodePointer doPredicate(EvalContext context, NodePointer parent, Step[] steps, int currentStep, Expression[] predicates, int currentPredicate)
      Evaluates predicates and proceeds with the subsequent steps of the path.
      Parameters:
      context - evaluation context
      parent - parent pointer
      steps - path steps
      currentStep - step number
      predicates - predicate expressions
      currentPredicate - int predicate number
      Returns:
      NodePointer
    • doPredicateName

      private static NodePointer doPredicateName(EvalContext context, NodePointer parent, Step[] steps, int currentStep, Expression[] predicates, int currentPredicate)
      Execute a NameAttributeTest predicate
      Parameters:
      context - evaluation context
      parent - parent pointer
      steps - path steps
      currentStep - int step number
      predicates - predicates
      currentPredicate - int predicate number
      Returns:
      NodePointer
    • doPredicatesStandard

      private static NodePointer doPredicatesStandard(EvalContext context, List parents, Step[] steps, int currentStep, Expression[] predicates, int currentPredicate)
      Called exclusively for standard InfoSet nodes, e.g. DOM nodes to evaluate predicate sequences like [@name=...][@name=...][index].
      Parameters:
      context - evaluation context
      parents - List of parent pointers
      steps - path steps
      currentStep - step number
      predicates - predicates
      currentPredicate - int predicate number
      Returns:
      NodePointer
    • doPredicateIndex

      private static NodePointer doPredicateIndex(EvalContext context, NodePointer parent, Step[] steps, int currentStep, Expression[] predicates, int currentPredicate)
      Evaluate a subscript predicate: see if the node is a collection and if the index is inside the collection.
      Parameters:
      context - evaluation context
      parent - parent pointer
      steps - path steps
      currentStep - step number
      predicates - predicates
      currentPredicate - int predicate number
      Returns:
      NodePointer
    • indexFromPredicate

      private static int indexFromPredicate(EvalContext context, Expression predicate)
      Extract an integer from a subscript predicate. The returned index starts with 0, even though the subscript starts with 1.
      Parameters:
      context - evaluation context
      predicate - to evaluate
      Returns:
      calculated index
    • keyFromPredicate

      private static String keyFromPredicate(EvalContext context, Expression predicate)
      Extracts the string value of the expression from a predicate like [@name=expression].
      Parameters:
      context - evaluation context
      predicate - predicate to evaluate
      Returns:
      String key extracted
    • computeQuality

      private static int computeQuality(NodePointer pointer)
      For a pointer that matches an actual node, returns 0. For a pointer that does not match an actual node, but whose parent pointer does returns -1, etc.
      Parameters:
      pointer - input pointer
      Returns:
      int match quality code
    • isNameAttributeEqual

      private static boolean isNameAttributeEqual(NodePointer pointer, String name)
      Returns true if the pointer has an attribute called "name" and its value is equal to the supplied string.
      Parameters:
      pointer - input pointer
      name - name to check
      Returns:
      boolean
    • isCollectionElement

      private static boolean isCollectionElement(NodePointer pointer, int index)
      Returns true if the pointer is a collection and the index is withing the bounds of the collection.
      Parameters:
      pointer - input pointer
      index - to check
      Returns:
      boolean
    • valuePointer

      private static NodePointer valuePointer(NodePointer pointer)
      For an intermediate pointer (e.g. PropertyPointer, ContainerPointer) returns a pointer for the contained value.
      Parameters:
      pointer - input pointer
      Returns:
      NodePointer
    • createNullPointer

      public static NodePointer createNullPointer(EvalContext context, NodePointer parent, Step[] steps, int currentStep)
      Creates a "null pointer" that a) represents the requested path and b) can be used for creation of missing nodes in the path.
      Parameters:
      context - evaluation context
      parent - parent pointer
      steps - path steps
      currentStep - step number
      Returns:
      NodePointer
    • createNullPointerForPredicates

      private static NodePointer createNullPointerForPredicates(EvalContext context, NodePointer parent, Step[] steps, int currentStep, Expression[] predicates, int currentPredicate)
      Creates a "null pointer" that starts with predicates.
      Parameters:
      context - evaluation context
      parent - parent pointer
      steps - path steps
      currentStep - step number
      predicates - predicates
      currentPredicate - int predicate number
      Returns:
      NodePointer
    • getNodeIterator

      private static NodeIterator getNodeIterator(EvalContext context, NodePointer pointer, Step step)
      Get a NodeIterator.
      Parameters:
      context - evaluation context
      pointer - owning pointer
      step - triggering step
      Returns:
      NodeIterator
    • isLangAttribute

      private static boolean isLangAttribute(QName name)
      Learn whether name is a lang attribute.
      Parameters:
      name - to compare
      Returns:
      boolean