Java is one of the most popular programming languages used for developing various applications and systems. It is known for its robustness, security, and platform independence. With each version, Java introduces new features and improvements to enhance the developer experience and meet the evolving needs of modern software development.

In the upcoming release of Java 22, there will be an extended support for foreign function and memory API, which provides developers with more flexibility and power to interact with native code and manipulate memory directly. This means that developers will have better control over low-level operations and can integrate their Java applications with existing C/C++ libraries more seamlessly.

Foreign Function API

The Foreign Function API, often referred to as the “FFI”, allows Java developers to call functions implemented in native code directly from Java. Previously, this was achieved through the Java Native Interface (JNI), which required writing a lot of boilerplate code and was often error-prone. With the new FFI, developers can simplify this process and write more concise and readable code.

Using FFI, developers can declare and invoke native functions with a simple syntax, as shown in the following example:

import jdk.incubator.foreign.*;
import java.lang.invoke.*;

public class NativeLibraryExample {
    public static void main(String[] args) throws Throwable {
        LibraryLookup lib =LibraryLookup.ofPath("/path/to/native/library.so");
        SymbolLookup symbols = lib.lookup(SymbolMatchers.prohibitLookup(""));
        MethodHandle mh = symbols.lookup("nativeFunction",FunctionType.of(ReturnType.name()));
        CallSite site = MHs.insertArguments(ExecuteNativeFunction.exactInvoker(mh), 0, functionArguments);
        ResultType result = (ResultType) site.dynamicInvoker().invoke();

        // Use the result as needed
    }
}

In this example, we first load the native library using LibraryLookup, then we lookup the symbol for the native function using SymbolLookup. We create a MethodHandle for the function and invoke it using ExecuteNativeFunction. Finally, we can use the result of the native function in our Java code.

Memory API

Along with the foreign function API, Java 22 also introduces an extended memory API, which allows developers to work directly with native memory. This means that developers can allocate, read, write, and manipulate memory regions outside of the Java heap.

The memory API provides various classes and methods to interact with native memory, such as MemorySegment for representing a contiguous region of memory, MemoryAddress for accessing individual memory locations, and MemoryLayout for describing the layout of structured data in memory.

Here’s an example that demonstrates the usage of the memory API:

import jdk.incubator.foreign.MemorySegment;

public class NativeMemoryExample {
    public static void main(String[] args) {
        try (MemorySegment segment = MemorySegment.allocateNative(1024)) {
            // Write data to native memory
            segment.asByteBuffer().putInt(0, 42);
            
            // Read data from native memory
            int value = segment.asByteBuffer().getInt(0);
            
            System.out.println("Value from native memory: " + value);
        }
    }
}

In this example, we allocate a native memory segment of size 1024 bytes using MemorySegment.allocateNative(). We then write an integer value of 42 to the native memory segment using ByteBuffer and read it back. Finally, we print the value obtained from native memory.

Conclusion

The extended support for foreign function and memory API in Java 22 opens up new possibilities for Java developers to interact with native code and work with native memory more efficiently. It simplifies the process of calling native functions and provides better control over low-level operations. This new feature will enable developers to integrate their Java applications with existing native libraries seamlessly and enhance the performance and capabilities of their applications.

With Java 22, Java continues to evolve as a versatile and powerful programming language, catering to the needs of modern software development.

References

• JEP 389: Foreign Function and Memory API (Incubator)
• Java Foreign Function and Memory API Documentation