Class SimplePathInterpreter


  • public class SimplePathInterpreter
    extends java.lang.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) $
    Author:
    Dmitri Plotnikov
    • Field Detail

      • QNAME_NAME

        private static final QName QNAME_NAME
    • Constructor Detail

      • SimplePathInterpreter

        public SimplePathInterpreter()
    • Method Detail

      • 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,
                                                        java.util.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 java.lang.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,
                                                    java.lang.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