Package com.invirgance.convirgance.transform

Interface Transformer

All Known Subinterfaces:
Filter, IdentityTransformer
All Known Implementing Classes:
AndFilter, CoerceStringsTransformer, ComparatorFilter, ContainsFilter, DateEpochTransformer, DateISOStringTransformer, EpochDateTransformer, EqualsFilter, GreaterThanFilter, GreaterThanOrEqualFilter, InsertKeyTransformer, ISOStringDateTransformer, LessThanFilter, LessThanOrEqualFilter, LikeFilter, NotFilter, OrFilter, SortedGroupByTransformer, UnsortedGroupByTransformer
public interface Transformer
An interface for applying lazy transformations to JSON objects during iteration. This enables efficient streaming transformations of data without loading entire collections into memory.

Transformations can include data cleaning, filtering, enrichment, or any other modifications to JSON objects. The transformations are applied on-the-fly as elements are accessed through the iterator.

Example usage:

 // Create a transformer that adds a timestamp to each record
 Transformer timestampTransformer = new Transformer() {
     public Iterator<JSONObject> transform(Iterator<JSONObject> iterator) {
         return new Iterator<JSONObject>() {
             public JSONObject next() {
                 JSONObject obj = iterator.next();
                 obj.put("timestamp", System.currentTimeMillis());
                 return obj;
             }
             // ... implement other Iterator methods
         };
     }
 };
Author:
jbanes

  • Method Details

    • transform

      default Iterable<JSONObject> transform(Iterable<JSONObject> iterable) throws ConvirganceException
      Provides a lazy transformation mechanism for an Iterable of JSON objects. The transformation is applied to each element only when it is accessed through the iterator.

      This default implementation wraps the iterator-based transformation, preserving the lazy evaluation semantics.

      Parameters:
      iterable - The source collection of JSON objects to transform.
      Returns:
      An Iterable that will apply transformations to elements when iterated.
      Throws:
      ConvirganceException - If an error occurs during transformation.

    • transform

      Iterator<JSONObject> transform(Iterator<JSONObject> iterator)
      Creates an iterator that transforms JSON objects as they are accessed. Implementations should maintain lazy evaluation by only transforming elements when they are requested through the iterator.

      The returned iterator should follow standard Iterator contract:

      • Only transform elements when next() is called
      • Throw NoSuchElementException if next() is called when hasNext() is false
      • Maintain consistent state between hasNext() and next() calls
      Parameters:
      iterator - The source iterator providing JSON objects to transform.
      Returns:
      An iterator that applies transformations to elements as they are accessed.