This part of the documentation describes various ways of customizing Nussknacker - from adding own Components to adding listeners for various Designer actions. The main way of adding customizations to Nussknacker is ServiceLoader
Please make sure to put jars with custom code on right classpath
- Customizations of model (in particular
ComponentProviders) can be loaded by adding libs/classes to dedicated
components/flink/extradirectory. For advanced usages, you can configure
modelConfig.classPathin Model config.
- Code of Designer customizations should go to the main Designer classpath (e.g. put the jars in the
Types of expressions are based on Java types. Nussknacker provides own abstraction of type, which can contain more information about given type than pure Java class - e.g. object type (like in Typescript) is represented in runtime as Java
Map, but during compilation we know the structure of this map.
We also handle union types (again, similar to Typescript) and we have
Unknown type which is represented as Java
Object in runtime, but behaves a bit like Typescript any (please note that
Unknown should be avoided as default Security settings settings prohibit omitting typechecking with
TypingResult is the main class (sealed trait) that represents type of expression in Nussknacker.
Typed object has many methods for constructing
Components and ComponentProviders
Components are main method of customizing Nussknacker. Components are created by configured
There are following types of components:
CustomStreamTransformer- types of transformations depend on type of Engine
Service- mainly for defining stateless enrichments To read more see ComponentProvider API
Deployment of scenarios
The Designer uses DeploymentManager
interface to perform actions on scenarios (deploy / cancel / etc.). All providers that are available in distribution deployment are located in
managers directory and are added to the Designer classpath.
If you want to implement own
DeploymentManager, you should implement this interface, package it, add to classpath and configure scenario type to use it. More info you can find on
Other SPIs for Nussknacker customization (documentation will follow soon...)
- Flink specific
Modules architecture and conventions
The diagram below shows dependencies between modules. You can see two main groups on it :
- API modules
API modules contains interfaces that are needed by our core modules (on both Designer and runtime side).
On the other hand Utils modules contain classes built on top of API which can be used in extensions but are not mandatory. API of Utils modules can be changed more often than API inside API modules
Both API modules and Utils modules have several modules with
-components part in name. They should be used to build own Components
nussknacker-scenario-api contains classes needed to operate on scenarios: creating it via DSL, marshalling to JSON, etc.
nussknacker-deployment-manager-api contains interfaces needed to create own DeploymentManager
that can be used to scenario execution.
nussknacker-extensions-* contains other extensions API.
Your code should depend only on
nussknacker-xxx-extensions-utils packages and not on implementation modules, like
nussknacker-lite-runtime or other
internal modules. They should only be needed in
If you find you need to depend on those modules, please bear in mind that they contain implementation details and their API should not be considered stable.
The plug-in jar should be fatjar containing all libraries necessary for running your customization,
except for dependencies provided by execution engine. In particular, for custom component implementation,
following dependencies should be marked as
provided and not be part of customization jar:
- All Nussknacker modules with names ending in
nussknacker-helpers-utils(are provided in
nussknacker-flink-components-utils(is provided in
- Basic Flink dependencies:
flink-statebackend-rocksdbetc. for Flink components (are provided in
nussknacker-kafka-utilsfor Streaming components in Lite engine
Please remember that
provided dependency are not transitive, i.e. if you depend on e.g.
you still have to declare dependency on
(see Maven documentation for further info).