Java applications often need integration with native libraries to access specialized functionality such as Off-CPU computing, graphics processing, machine learning frameworks, or System level APIs. While the Java ecosystem provides numerous powerful libraries, there exist numerous robust, native-only libraries that are not, will not and should not be rewritten in Java. Java's Foreign Function & Memory (FFM) API, finalized in JDK 22, enables Java developers to interface safely and efficiently with native code.

However, creating Java bindings manually using the FFM tedious and error-prone, as one would need to know the layouts of all the native types involved. jextract addresses this challenge by automatically generating Java bindings from existing C headers.

The session briefly illustrates the types of bindings generated by jextract for common C constructs such as structs, nested structs, functions, variadic functions, typedefs, built-in types, and the recommended workflow. It also includes live demos where Java client code uses jextract-generated FFM bindings to interact with native libraries, such as running machine learning inference using ONNXRuntime-genAI and performing GPU-accelerated CUDA nbody simulations using a fully jextracted OpenCL and OpenGL backend.

Participants will leave understanding how jextract allows developers to ""move the seam" between Java and native code.