Lucidworks provides a Connectors SDK in a public repository on GitHub with all the resources you need to develop custom connectors. Clone the repository to get started:
git clone https://github.com/lucidworks/connectors-sdk-resources
It includes the Random Content connector, which generates random documents and serves as an example project that you can use as a model for your own custom connector projects.
Currently, only Java is supported. See the Javadocs.
These topics provide details about developing custom connectors for Fusion: