Use array from Java as method argument to .NET DLL

This article shows how to pass array as an argument.

Javonet allows you to reference and use modules or packages written in (Java/Kotlin/Groovy/Clojure, C#/VB.NET, Ruby, Perl, Python, JavaScript/TypeScript) like they were created in your technology. If have not yet created your first project check Javonet overview and quick start guides for your technology.

Custom .NET DLL with method accepting array

With Javonet it is possible to reference any custom .NET DLL and interact with arrays declared on types defined within that module almost the same as with any other Java library.

Snippet below represents the sample code from .NET DLL that has methods which return or process the arrays:

public string[] Get1DArray()
{
	return new string[] { "one", "two", "three", "four", "five" };
}

public string[,] Get2DArray()
{
	return new string[,] { { "S00", "S01" }, { "S10", "S11" } };
}

public double AddArrayElementsAndMultiply(double[] myArray, double myValue)
{
	double sum = 0;
	foreach (double element in myArray)
	{
		sum += element;
	}

	return sum * myValue;
}

With Javonet SDK it is possible to pass array as an argument to one of this method.

Pass Java array

I code in:
// use activate only once in your app
Javonet.activate("your-license-key");

// create called runtime context
RuntimeContext calledRuntime = Javonet.inMemory().netcore();

// set up variables
String libraryPath = resourcesDirectory + "/TestClass.dll";
String className = "TestClass.TestClass";

// load custom library
calledRuntime.loadLibrary(libraryPath);

// get type from runtime
InvocationContext calledRuntimeType = calledRuntime.getType(className).execute();

// create type's instance
InvocationContext instance = calledRuntimeType.createInstance().execute();

// invoke instance's method
InvocationContext response = instance
        .invokeInstanceMethod("AddArrayElementsAndMultiply", new Double[] { 12.22, 98.22, -10.44 }, 9.99)
        .execute();

// get value from response
double result = (double) response.getValue();

// write result to console
System.out.println(result);

In the snippet above, addArrayElementsAndMultiply method needs array to be the first argument. Depending on called technology, the array may need to have a specific type, f. e. array of doubles. In this case, proper cast is needed before passing the array from Java.

The same operation can be performed remotely by just changing the new Runtime Context invocation from in memory to tcp that will create and interact with your .NET DLL objects on any remote node, container or service that hosts Javonet Code Gateway. This way you can preserve the same logic in your application and instantly switch between monolithic and microservices architecture without the need to implement the integration layer based on web services or other remote invocation methods.

Read more about use cases and software architecture scenarios where Javonet runtime bridging technology can support your development process.

Additional references