Developing Java™ native functions

You create Java™ native functions by adding Java™ annotations that describe Java™ public static methods as native functions to the SPL compiler.

You compile the Java™ source code and index the toolkit by running the spl-make-toolkit command or the sc command. Then, Teracloud® Streams creates the necessary toolkit artifacts that enable SPL code to call the Java™ method directly with the same syntax that is used to call an SPL function.

To define a Java™ public static method as a native function, add the @Function annotation to a public static method in the Java™ source code. If the function uses external libraries, you can also add the @ToolkitLibraries annotation to the containing class to specify the locations of the libraries.

@Function (namespace=”spl.math.java”)
public static double pow(double x, double y) {
   return Math.pow(x, y);
}

In the previous Java™ example, the @Function annotation has the optional namespace attribute. When the namespace attribute is omitted, SPL gets the values for that attribute from the value of the @Namespace annotation for the package of the annotated method, if it exists. Otherwise, SPL gets the values for the namespace attribute from the package name of the annotated method.

use spl.math.java::*;
float64 res = pow(1.5, 3.1);

public class JavaFunctions {
  @Function(name="getUser", description="Return value of USER environment variable")
  public static String getUser() {
    return System.getenv("USER");
}

When the Java™ compiler compiles the Java™ source, the annotation processing creates a nested class for the class that contains the annotated method. The nested class is named class_name$StreamsModel. When the toolkit index is rebuilt, SPL artifacts are created under the SPL_namespace/native.function directory.

For more information about creating a Java™ native function, see the API documentation for the com.ibm.streams.function.model package.