com.bazaarvoice.jolt.traversr

Class Traversr

java.lang.Object

com.bazaarvoice.jolt.traversr.Traversr

Direct Known Subclasses:

SimpleTraversr

public abstract class Traversr
extends Object

Traversr allows you to walk JSON tree structures of data, and to GET and SET operations. Corner cases that arise during tree walk, are handled by subclasses. Ex: If no data exists mid tree walk quit or insert a new container? Or if there is data but it is the wrong type : overwrite or skip? Traversr analyzes the path path to be traversed and creates a "linked list" of Traversal objects. Then that list of Traversals can be used many times to write data into different JSON tree structures with different key values. For example given a Shiftr output path of : "tuna[&1].bob.&3[]" some of the keys are known, "tuna" and "bob", but other keys will only be known later. However, the structure of the output path will not change, which means we can do some work before the keys are known. First the output path is turned into its canonical form : "tuna.[4].[&1].bob.&3.[]". Then, a series of Traversals is created. tuna -> MapTraversal [&1] -> ArrayTraversal bob -> MapTraversal &3 -> MapTraversal [] -> AutoExpandArrayTraversal Later, a list of keys can then be provided, such as [ "tuna", "2", "bob", "smith", "[]" ], and they can be quickly used without having to build or parse any more objects. The list of keys are all Strings, which ArrayTraversals will convert to Integers as needed.

Constructor Summary

Constructors

Constructor and Description
Traversr(String humanPath)

Method Summary

Methods

Modifier and Type	Method and Description
Object	get(Object tree, List<String> keys) Note : Calling this method MAY modify the tree object by adding new Maps and Lists as needed for the traversal.
abstract Object	handleFinalSet(TraversalStep traversalStep, Object tree, String key, Object data) Allow subclasses to control how "sets" are done, if/once the traversal has made it to the the last element.
abstract Object	handleIntermediateGet(TraversalStep traversalStep, Object tree, String key, TraversalStep.Operation op) Allow subclasses to control how gets are handled for intermediate traversals.
Object	remove(Object tree, List<String> keys) Note : Calling this method MAY modify the tree object by adding new Maps and Lists as needed for the traversal.
Object	set(Object tree, List<String> keys, Object data)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Traversr

public Traversr(String humanPath)

Method Detail

get

public Object get(Object tree,
         List<String> keys)

Note : Calling this method MAY modify the tree object by adding new Maps and Lists as needed for the traversal. This is determined by the behavior of the implementations of the abstract methods of this class.

Returns:

null or data

set

public Object set(Object tree,
         List<String> keys,
         Object data)

Parameters:

tree - tree of Map and List JSON structure to navigate

data - JSON style data object you want to set

Returns:

returns the data object if successfully set, otherwise null if there was a problem walking the path

remove

public Object remove(Object tree,
            List<String> keys)

Note : Calling this method MAY modify the tree object by adding new Maps and Lists as needed for the traversal. This is determined by the behavior of the implementations of the abstract methods of this class.

Returns:

null or data

handleFinalSet

public abstract Object handleFinalSet(TraversalStep traversalStep,
                    Object tree,
                    String key,
                    Object data)

Allow subclasses to control how "sets" are done, if/once the traversal has made it to the the last element. Overwrite existing data? List-ize existing data with new data?

Returns:

the data object if the set was successful, or null if not

handleIntermediateGet

public abstract Object handleIntermediateGet(TraversalStep traversalStep,
                           Object tree,
                           String key,
                           TraversalStep.Operation op)

Allow subclasses to control how gets are handled for intermediate traversals. Example: we are a MapTraversal and out key is "foo". We simply do a 'tree.get( "foo" )'. However, if we get a null back, or we get back a data type incompatible with our child Traversal, what do we do? Overwrite or just return?

Returns:

null or a container object (Map/List) for our child Traversal to use