Package org.apache.commons.jxpath.ri.compiler

Class Path

  • Direct Known Subclasses:
    ExpressionPath, LocationPath
    public abstract class Path
extends Expression
    Version:
    $Revision: 681111 $ $Date: 2008-07-30 11:30:29 -0500 (Wed, 30 Jul 2008) $

    • Field Detail

      • steps

        private Step[] steps

      • basicKnown

        private boolean basicKnown

      • basic

        private boolean basic

    • Constructor Detail

      • Path

        public Path​(Step[] steps)
        Create a new Path.
        Parameters:
        steps - that compose the Path

    • Method Detail

      • getSteps

        public Step[] getSteps()
        Get the steps.
        Returns:
        Step[]

      • computeContextDependent

        public boolean computeContextDependent()
        Description copied from class: Expression
        Implemented by subclasses and result is cached by isContextDependent()
        Specified by:
        computeContextDependent in class Expression
        Returns:
        calculated context-dependentness as boolean

      • isSimplePath

        public boolean isSimplePath()
        Recognizes paths formatted as foo/bar[3]/baz[@name = 'biz']. The evaluation of such "simple" paths is optimized and streamlined.
        Returns:
        true if this path is simple

      • isSimpleStep

        protected boolean isSimpleStep​(Step step)
        A Step is "simple" if it takes one of these forms: ".", "/foo", "@bar", "/foo[3]". If there are predicates, they should be context independent for the step to still be considered simple.
        Parameters:
        step - the step to check
        Returns:
        boolean

      • areBasicPredicates

        protected boolean areBasicPredicates​(Expression[] predicates)
        Learn whether the elements of the specified array are "basic" predicates.
        Parameters:
        predicates - the Expression[] to check
        Returns:
        boolean

      • getSingleNodePointerForSteps

        protected Pointer getSingleNodePointerForSteps​(EvalContext context)
        Given a root context, walks a path therefrom and finds the pointer to the first element matching the path.
        Parameters:
        context - evaluation context
        Returns:
        Pointer

      • searchForPath

        protected Pointer searchForPath​(EvalContext context)
        The idea here is to return a NullPointer rather than null if that's at all possible. Take for example this path: "//map/key". Let's say, "map" is an existing node, but "key" is not there. We will create a NullPointer that can be used to set/create the "key" property.

        However, a path like "//key" would still produce null, because we have no way of knowing where "key" would be if it existed.

        To accomplish this, we first try the path itself. If it does not find anything, we chop off last step of the path, as long as it is a simple one like child:: or attribute:: and try to evaluate the truncated path. If it finds exactly one node - create a NullPointer and return. If it fails, chop off another step and repeat. If it finds more than one location - return null.

        Parameters:
        context - evaluation context
        Returns:
        Pointer

      • evalSteps

        protected EvalContext evalSteps​(EvalContext context)
        Given a root context, walks a path therefrom and builds a context that contains all nodes matching the path.
        Parameters:
        context - evaluation context
        Returns:
        EvaluationContext

      • buildContextChain

        protected EvalContext buildContextChain​(EvalContext context,
                                        int stepCount,
                                        boolean createInitialContext)
        Build a context from a chain of contexts.
        Parameters:
        context - evaluation context
        stepCount - number of steps to descend
        createInitialContext - whether to create the initial context
        Returns:
        created context

      • createContextForStep

        protected EvalContext createContextForStep​(EvalContext context,
                                           int axis,
                                           NodeTest nodeTest)
        Different axes are serviced by different contexts. This method allocates the right context for the supplied step.
        Parameters:
        context - evaluation context
        axis - code
        nodeTest - node test
        Returns:
        EvalContext