Fortanix Data Security Manager (DSM) provides multiple interfaces to application developers. For C/C++ programmers, Fortanix DSM provides a PKCS#11 interface through a library. For Java programmers, Fortanix DSM can be accessed through the JCE interface and through Java SDK. Fortanix DSM can also be accessed through its RESTful interface, documented at https://www.fortanix.com/api/
The example programs can be downloaded in full on the Downloads page.