This module contains Gaffer's data objects: Element, Edge and Entity.

It also contains the logic for processing these Elements - ElementAggregator, ElementFilter and ElementTransformer.

Functions and Predicates

Gaffer makes use of Java 8's Function and Predicate interfaces to aggregate, transform and filter data. To allow these Function and Predicate classes to process tuples we make use of the Koryphe library. Koryphe allows us to wrap the Gaffer Elements in a tuple and pass it any Function or Predicate.

You can use any of our implementations (see Predicate Examples) or write your own.

All of the following classes will act on one or more Element identifiers (vertex/source/destination/directed) or properties. If you implement the Java 8 interfaces directly, you would need to add the following JsonType annotation to your class:

@JsonTypeInfo(use = JsonTypeInfo.Id.CLASS, include = JsonTypeInfo.As.PROPERTY, property = "class")

Instead, we recommend you implement the Koryphe interfaces instead, which will add this annotation in for you.


Aggregation is done using a KorypheBinaryOperator<T> (or just BinaryOperator<T>), where T is the type of the property you are aggregating. For example: Max.


Transforms are applied using KorypheFunction<I, O> (or just Function<I, O>), where I is type of the input property and O is the type of the output value. If you want to transform multiple properties into a single new property then you can implement KorypheFunction2<T, U, R> or KoryphePredicate3<T, U, V, R>, etc. where R is the output value type. For example: Concat.


Filtering is applied using KoryphePredicate<T> (or just Predicate<T>), where T is type of the property you want to filter on. If you want to filter on multiple properties then you can implement KoryphePredicate2<T, U> or KoryphePredicate3<T, U, V> etc. For example: Exists.

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