Iterate over Java array from .NET DLL

This article shows how to iterate over array from called technology.

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 array handling

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;
}

Iterate Java array from .NET DLL

With Javonet SDK it is possible to iterate over array from called technology and invoke methods on its elements.

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 array = instance.invokeInstanceMethod("Get1DArray").execute();

// get array's size
int arraySize = (int) array.getSize().execute().getValue();

// create local array and store elements in it
String[] arrayValues = new String[arraySize];
int i = 0;
for (InvocationContext element : array) {
    arrayValues[i] = (String) element.invokeInstanceMethod("ToUpper").execute().getValue();
    i++;
}

// write result to console
System.out.println(String.join("\t", arrayValues));

In the snippet above, get1DArray method is used to get reference to 1D array from .NET DLL. This reference can be used to iterate over array's elements and optionally invoke methods on the elements.

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