Package org.terracotta.context.query

Class QueryBuilder

  • public class QueryBuilder
extends java.lang.Object
    A QueryBuilder allows for modular assembly of context graph queries.

    Query assembly is performed by chaining a sequence of graph traversal and filtering operations together in order to select a particular set of the input node set's descendants.

    • Field Detail

      • current

        private Query current

    • Constructor Detail

      • QueryBuilder

        private QueryBuilder()

    • Method Detail

      • queryBuilder

        public static QueryBuilder queryBuilder()
        Creates a new query builder instance.

        A newly constructed query builder represents the identity query. It simply returns the input node set as the output node set.

        Returns:
        a new query builder

      • filter

        public QueryBuilder filter​(Matcher<? super TreeNode> filter)
        Filters the current node set using the supplied Matcher.

        Nodes in the current node set that are not selected by the supplied matcher are removed.

        Parameters:
        filter - matcher to apply
        Returns:
        this query builder

      • children

        public QueryBuilder children()
        Selects the union of the current node sets child nodes.
        Returns:
        this query builder

      • parent

        public QueryBuilder parent()
        Selects the parent of the current node.
        Returns:
        this query builder

      • descendants

        public QueryBuilder descendants()
        Selects the merged descendant set of the current node set.

        More precisely this recursively merges the children of each member of the node-set in to the output node set until the set ceases to grow.

        Returns:
        this query builder

      • chain

        public QueryBuilder chain​(Query query)
        Applies the given query on the currently selected node set.
        Parameters:
        query - query to apply
        Returns:
        this query builder

      • ensureUnique

        public QueryBuilder ensureUnique()
        Asserts that the current node set is a singleton.

        If the current node set is not of size 1 then the query will terminate with an IllegalStateException.

        Returns:
        this query builder

      • empty

        public QueryBuilder empty()
        Selects an empty node set.
        Returns:
        this query builder

      • build

        public Query build()
        Returns a query that represents the currently assembled transformation.
        Returns:
        a newly constructed query