Extending OpenRocket

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Extending OpenRocket

OpenRocket is built to be extensible using plugins. You can implement your own functionality or download plugins implemented by others.

This document describes how to implement your own extensions to OpenRocket.


Extensions to OpenRocket are implemented as plugins. All interfaces that may have multiple implementations should be implemented using plugin interfaces internally. That way, external plugins may create new implementations.

A plugin is compiled into a JAR file and placed into the OpenRocket plugin directory. These JAR files are included in the OpenRocket classpath at startup and scanned for classes and interfaces annotated with @Plugin.

  • A plugin interface is a Java interface that is annotated with the @Plugin annotation. These interfaces are scanned from the classpath at startup and can be queried by the code.
  • A plugin implementation is a Java class that implements a plugin interface and is annotated with the @Plugin annotation.

In practise the plugin interfaces are defined by the internal OpenRocket code, and are extension points which internal and external plugins can implement.

Note: Many of the internal interfaces have not yet been changed to use the plugin interface. They will be migrated one by one. Help is appreciated.

Simulation extensions

Simulation extensions allow modifying simulations before or during a simulation. They allow controlling almost every aspect of a simulation.

A simulation extensions typically consists of 2-4 Java classes:

  • The simulation extension implements the SimulationExtension interface. A new instance is created for each simulation that has the extension defined. It contains the extension configuration and a method that is called whenever a simulation is started.
  • The simulation extension provider is a plugin implementation that functions as a factory class for the simulation extension. It implements the SimulationExtensionProvider interface.
  • A simulation extension configurator is an optional plugin implementation that provides a GUI for configuring a simulation extension. It implements the SwingSimulationExtensionConfigurator interface.
  • A simulation listener is a listener that is attached to a simulation at runtime. The listener is notified of all actions during the simulation and it can modify and affect the simulation while it is being run. The simulation extension may add a simulation listener to the simulation run when it is started. A simulation listener implements one or more of the interfaces SimulationListener, SimulationComputationListener and SimulationEventListener.

The recommended way of implementing these interfaces is by extending the abstract classes AbstractSimulationExtension, AbstractSimulationExtensionProvider, AbstractSwingSimulationExtensionConfigurator and AbstractSimulationListener. This allows maximum compatibility with future versions of OpenRocket when new methods are added to the interfaces.