Package graphql.util

Interface TraverserContext<T>

  • Type Parameters:
    T - type of tree node
    All Known Implementing Classes:
    DefaultTraverserContext
    @PublicApi
public interface TraverserContext<T>
    Traversal context. It is used as providing context for traversing, but also for returning an accumulate value. (setAccumulate(Object) There is always a "fake" root context with null node, null parent, null position. See isRootContext()

    • Method Detail

      • thisNode

        T thisNode()
        Returns current node being visited. Special cases: It is null for the root context and it is the changed node after changeNode(Object) is called. Throws Exception if the node is deleted.
        Returns:
        current node traverser is visiting.
        Throws:
        AssertException - if the current node is deleted

      • originalThisNode

        T originalThisNode()
        Returns the original, unchanged, not deleted Node.
        Returns:
        the original node

      • changeNode

        void changeNode​(T newNode)
        Change the current node to the provided node. Only applicable in enter. Useful when the tree should be changed while traversing. Also: changing a node makes only a difference when it has different children than the current one.
        Parameters:
        newNode - the new Node

      • deleteNode

        void deleteNode()
        Deletes the current node.

      • isDeleted

        boolean isDeleted()
        Returns:
        true if the current node is deleted (by calling deleteNode()

      • isChanged

        boolean isChanged()
        Returns:
        true if the current node is changed (by calling changeNode(Object)

      • getParentContext

        TraverserContext<T> getParentContext()
        Returns parent context. Effectively organizes Context objects in a linked list so by following getParentContext() links one could obtain the current path as well as the variables getVar(java.lang.Class) stored in every parent context.
        Returns:
        context associated with the node parent

      • getParentNodes

        java.util.List<T> getParentNodes()
        The list of parent nodes starting from the current parent.
        Returns:
        list of parent nodes

      • getParentNode

        T getParentNode()
        The parent node.
        Returns:
        The parent node.

      • getBreadcrumbs

        java.util.List<Breadcrumb<T>> getBreadcrumbs()
        The exact location of this node inside the tree as a list of Breadcrumb
        Returns:
        list of breadcrumbs. the first element is the location inside the parent.

      • getLocation

        NodeLocation getLocation()
        The location of the current node regarding to the parent node.
        Returns:
        the position or null if this node is a root node

      • isVisited

        boolean isVisited()
        Informs that the current node has been already "visited"
        Returns:
        true if a node had been already visited

      • getVar

        <S> S getVar​(java.lang.Class<? super S> key)
        Obtains a context local variable
        Type Parameters:
        S - type of the variable
        Parameters:
        key - key to lookup the variable value
        Returns:
        a variable value or null

      • getVarFromParents

        <S> S getVarFromParents​(java.lang.Class<? super S> key)
        Searches for a context variable starting from the parent up the hierarchy of contexts until the first variable is found.
        Type Parameters:
        S - type of the variable
        Parameters:
        key - key to lookup the variable value
        Returns:
        a variable value or null

      • setVar

        <S> TraverserContext<T> setVar​(java.lang.Class<? super S> key,
                               S value)
        Stores a variable in the context
        Type Parameters:
        S - type of a variable
        Parameters:
        key - key to create bindings for the variable
        value - value of variable
        Returns:
        this context to allow operations chaining

      • setAccumulate

        void setAccumulate​(java.lang.Object accumulate)
        Sets the new accumulate value. Can be retrieved by getNewAccumulate()
        Parameters:
        accumulate - to set

      • getCurrentAccumulate

        <U> U getCurrentAccumulate()
        The current accumulate value used as "input" for the current step.
        Type Parameters:
        U - and me
        Returns:
        the current accumulate value

      • getSharedContextData

        <U> U getSharedContextData()
        Used to share something across all TraverserContext.
        Type Parameters:
        U - and me
        Returns:
        contextData

      • isRootContext

        boolean isRootContext()
        Returns true for the root context, which doesn't have a node or a position.
        Returns:
        true for the root context, otherwise false

      • getChildrenContexts

        java.util.Map<java.lang.String,​java.util.List<TraverserContext<T>>> getChildrenContexts()
        In case of leave returns the children contexts, which have already been visited.
        Returns:
        the children contexts. If the childs are a simple list the key is null.

      • getPhase

        TraverserContext.Phase getPhase()
        Returns:
        the phase in which the node visits currently happens (Enter,Leave or BackRef)

      • isParallel

        boolean isParallel()
        Returns:
        true if the traversing happens in parallel (multi threaded) or not.