This project demonstrates how to build a plugin for the Rocana transformation engine. Plugins can perform arbitrary processing on event data within the system.
Before you start, we assume the following:
- An intermediate knowledge of Java 7 or later.
- An intermediate understanding of Apache Maven.
- A basic understanding of JUnit.
A transformation plugin consists of two primary classes: an Action and an
ActionBuilder.
An implementation of the Action interface contains the logic for how to process
individual events. Actions are free to contain any kind of logic, although they
should avoid expensive calls to external services or APIs as they are executed
for every event that passes through the system. See the class MyAction in this
project for a simple Action that uppercases a message and sets a context
variable other Actions may reference later in the transformation.
An ActionBuilder implementation is responsible for holding configuration
information and creating new instances of an appropriate Action. In almost all
cases, there is a one to one relationship between Actions and ActionBuilders.
ActionBuilders are annotated with Rocana Configuration annotations that specify
configuration property names and types. See MyActionBuilder in this project for
a simple example of an ActionBuilder.
Upon startup, the Rocana transformation engine uses the Java ServiceLoader
facility to find and instantiate ActionBuilders. This is how ActionBuilders are
found at runtime. If you're not familiar with the ServiceLoader facility, you
can get away with just specifying the fully qualified class name of the
ActionBuilder implementation in the file named com.rocana.transform.conf.ActionBuilder
in the src/main/resources/META-INF/services/ directory in this project.
An example configuration that uses MyAction is provided in
src/test/resources/test-my-action.conf.
Finally, a test of the MyAction plugin TestMyAction is included. This test
mimics how Rocana components invoke the transformation engine making it suitable
to test custom Actions. You may customize the types of events used as inputs
to the transformation engine to test specific use cases.
This project is managed by Maven.
To build the project, run its tests, and assemble its output, run:
mvn package
To clean any temporary build files, run:
mvn clean
To build the project and assemble its output, but skip tests, run:
mvn package -DskipTests
This project is licensed under the Apache License 2.0. See the included LICENSE file for full details.