Use instance fields and properties from NodeJs package in GoLang app

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 NodeJs package like they were available in GoLang but invocation must be performed through Javonet SDK API.

Javonet allows you to pass any GoLang value type as argument to method from NodeJs 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.

Custom NodeJs package with instance fields and properties

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

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

const fs = require('fs').promises;

class TestClass {

    publicValue;
    #privateValue;
    static staticValue = 3;
    
    constructor(first, second) {
    	this.publicValue = first;
    	this.#privateValue = second;
    }
}

module.exports = TestClasspublicValue;
#privateValue;
static staticValue = 3;

constructor(first, second) {
	this.publicValue = first;
	this.#privateValue = second;
}

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

package main

import (
	"fmt"
	Javonet "javonet.com/javonet"
)

var resourcesDirectory string = "."

func main() {
	_ = resourcesDirectory

  	// use Activate only once in your app
  	Javonet.Activate("your-license-key")
  	
  	// create called runtime context
  	calledRuntime, _ := Javonet.InMemory().Nodejs()
  	
  	// set up variables
  	libraryPath := resourcesDirectory + "/TestClass.js"
  	className := "TestClass"
  	
  	// load custom library
  	calledRuntime.LoadLibrary(libraryPath)
  	
  	// get type from the runtime
  	calledRuntimeType, _ := calledRuntime.GetType(className).Execute()
  	
  	// create type's instance
  	instance, _ := calledRuntimeType.CreateInstance(18, 19).Execute()
  	
  	// get instance's field
  	response, _ := instance.GetInstanceField("publicValue").Execute()
  	
  	// get value from response
  	result := response.GetValue().(int32)
  	
  	// write result to console
  	fmt.Println(result)
}
const fs = require('fs').promises;

class TestClass {

    publicValue;
    #privateValue;
    static staticValue = 3;
    
    constructor(first, second) {
    	this.publicValue = first;
    	this.#privateValue = second;
    }
}

module.exports = TestClass// use Activate only once in your app
Javonet.Activate("your-license-key")

// create called runtime context
calledRuntime, _ := Javonet.InMemory().Nodejs()

// set up variables
libraryPath := resourcesDirectory + "/TestClass.js"
className := "TestClass"

// load custom library
calledRuntime.LoadLibrary(libraryPath)

// get type from the runtime
calledRuntimeType, _ := calledRuntime.GetType(className).Execute()

// create type's instance
instance, _ := calledRuntimeType.CreateInstance(18, 19).Execute()

// get instance's field
response, _ := instance.GetInstanceField("publicValue").Execute()

// get value from response
result := response.GetValue().(int32)

// write result to console
fmt.Println(result)

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

package main

import (
	"fmt"
	Javonet "javonet.com/javonet"
)

var resourcesDirectory string = "."

func main() {
	_ = resourcesDirectory

  	// use Activate only once in your app
  	Javonet.Activate("your-license-key")
  	
  	// create called runtime context
  	calledRuntime, _ := Javonet.InMemory().Nodejs()
  	
  	// set up variables
  	libraryPath := resourcesDirectory + "/TestClass.js"
  	className := "TestClass"
  	
  	// load custom library
  	calledRuntime.LoadLibrary(libraryPath)
  	
  	// get type from the runtime
  	calledRuntimeType, _ := calledRuntime.GetType(className).Execute()
  	
  	// create type's instance
  	instance, _ := calledRuntimeType.CreateInstance(18, 19).Execute()
  	
  	// set instance's field
  	instance.SetInstanceField("publicValue", 44).Execute()
  	
  	// get instance's field
  	response, _ := instance.GetInstanceField("publicValue").Execute()
  	
  	// get value from response
  	result := response.GetValue().(int32)
  	
  	// write result to console
  	fmt.Println(result)
}
const fs = require('fs').promises;

class TestClass {

    publicValue;
    #privateValue;
    static staticValue = 3;
    
    constructor(first, second) {
    	this.publicValue = first;
    	this.#privateValue = second;
    }
}

module.exports = TestClass// use Activate only once in your app
Javonet.Activate("your-license-key")

// create called runtime context
calledRuntime, _ := Javonet.InMemory().Nodejs()

// set up variables
libraryPath := resourcesDirectory + "/TestClass.js"
className := "TestClass"

// load custom library
calledRuntime.LoadLibrary(libraryPath)

// get type from the runtime
calledRuntimeType, _ := calledRuntime.GetType(className).Execute()

// create type's instance
instance, _ := calledRuntimeType.CreateInstance(18, 19).Execute()

// set instance's field
instance.SetInstanceField("publicValue", 44).Execute()

// get instance's field
response, _ := instance.GetInstanceField("publicValue").Execute()

// get value from response
result := response.GetValue().(int32)

// write result to console
fmt.Println(result)

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

Framework instance fields and properties

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

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 NodeJs 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.

Use instance fields and properties from NodeJs package in GoLang app

Custom NodeJs package with instance fields and properties

Framework instance fields and properties

Additional references