Create generic Java class instance from .NET Framework DLL

This article provides an introduction to cross-technology handling of generic class instance. A generic class in programming is a class that can work with any data type. The data type is specified as a parameter at the time of creating an instance of the class. This allows for type-safe code reusability. A single class or method can be used with different data types without the need for multiple implementations. It is described in detail in article about generic classes in .NET and article about generics in Java.

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.

With Javonet you can interact with generic classes from .NET Framework DLL like they were available in Java but invocation must be performed through Javonet SDK API.

Javonet allows you to pass any Java value type as argument to method from .NET Framework DLL. For reference type arguments (instances of other classes) you can create such instance with Javonet and pass the Invocation Context variable referencing that object as argument of method invocation.

Generic Java class from framework

It is possible to create generic class instance and interact with its methods from netframework-dll framework using following Java code:

import com.javonet.sdk.*;

public class SampleProgram {

    private static final String resourcesDirectory = ".";
    public static void main(String []args) {

        // use activate only once in your app
        Javonet.activate("your-license-key");
        
        // create called runtime context
        RuntimeContext calledRuntime = Javonet.inMemory().clr();
        
        // get string type
        InvocationContext stringType = calledRuntime.getType("System.String");
        
        // get generic calls with string type as parameter
        InvocationContext listType = calledRuntime.getType("System.Collections.Generic.List`1", stringType);
        
        // create generic type's instance
        InvocationContext list = listType.createInstance().execute();
        
        // invoke instance's methods
        list.invokeInstanceMethod("Add", "one").execute();
        list.invokeInstanceMethod("Add", "two").execute();
        list.invokeInstanceMethod("Add", "three").execute();
        list.invokeInstanceMethod("AddRange", (Object)new String[]{"four", "five", "six"}).execute();
        
        // check number of elements
        int count = (int) list.getInstanceField("Count").execute().getValue();
        
        // write result to console
        System.out.println(count);
     }
}namespace TestClass
{
	public class TestClass
	{
		public TestClass() { }

		// empty
	}
}
// use activate only once in your app
Javonet.activate("your-license-key");

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

// get string type
InvocationContext stringType = calledRuntime.getType("System.String");

// get generic calls with string type as parameter
InvocationContext listType = calledRuntime.getType("System.Collections.Generic.List`1", stringType);

// create generic type's instance
InvocationContext list = listType.createInstance().execute();

// invoke instance's methods
list.invokeInstanceMethod("Add", "one").execute();
list.invokeInstanceMethod("Add", "two").execute();
list.invokeInstanceMethod("Add", "three").execute();
list.invokeInstanceMethod("AddRange", (Object)new String[]{"four", "five", "six"}).execute();

// check number of elements
int count = (int) list.getInstanceField("Count").execute().getValue();

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

This snippet uses in memory runtime bridging to start called technology.
Next, instance of generic class is created. While creating instance of .NET generic class it is necessary to pass method name, type and arguments.
While creating instance of Java generic class it is necessary to pass method name and arguments.
Next, instance method are invoked to interact with created instance.
Finally, the result is printed to console.

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 Framework 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.