Instance fields and properties

This article provides an introduction to cross-technology handling of static fields and properties.
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 instance field and properties from Ruby package 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 Ruby package. 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.

Get/Set instance field from custom Ruby package

With Javonet it is possible to reference any custom Ruby package and interact with public instance fields and properties declared on types defined within that module almost the same as with any other Java library.

Snippet below represents the sample code from Ruby package which contains class with fields:

@@static_value = 3
@public_value
@private_value

def initialize(public_value = 0, private_value = 0)
  @public_value = public_value
  @private_value = private_value
end

It is possible to get one of the declared instance fields from Ruby package using following Java code.

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

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

// set up variables
String libraryPath = resourcesDirectory + "/TestClass.rb";
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(18, 19).execute();

// get instance's field
InvocationContext response = instance.getInstanceField("public_value").execute();

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

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

This uses in memory runtime bridging to load the Ruby package, and next retrieves reference to specific type and gets the instance field. Result of the invocation is returned as regular Java value and can be used for further processing. It is possible to set one of the declared instance fields from Ruby package using following Java code.

I code in:
Javonet.activate("your-license-key");

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

// set up variables
String libraryPath = resourcesDirectory + "/TestClass.rb";
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(18, 19).execute();

// set instance's field
instance.setInstanceField("public_value", 44).execute();

// get instance's field
InvocationContext response = instance.getInstanceField("public_value").execute();

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

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

This uses in memory runtime bridging to load the Ruby package, and next retrieves reference to specific type, then sets and gets the instance field. Result of the invocation is returned as regular Java value and can be used for further processing.

Get/Set instance field from standard Ruby package

The same steps are required to get types and fields from framework Ruby package:

I code in:

This snippet doesn't support selected combination of technologies.

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 Ruby package 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