Static fields and properties from JAR library in GoLang

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 static field and properties from JAR library like they were available in GoLang but invocation must be performed through Javonet SDK API.

Get/Set static field from custom JAR library in GoLang

With Javonet it is possible to reference any custom JAR library and interact with public static 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 JAR library which contains class with fields:

public int publicValue;
private int privateValue;
public static int staticValue = 3;

public TestClass(int publicValue, int privateValue) {
	this.publicValue = publicValue;
	this.privateValue = privateValue;
}

It is possible to get one of the declared static fields from JAR library using following GoLang code.

// use Activate only once in your app
Javonet.ActivateWithCredentials("your-license-key")

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

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

// load custom library
calledRuntime.LoadLibrary(libraryPath)

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

// get type's static field
response, _ := calledRuntimeType.GetStaticField("staticValue").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 JAR library, and next retrieves reference to specific type and gets the static 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 static fields from JAR library using following GoLang code.

// use Activate only once in your app
Javonet.ActivateWithCredentials("your-license-key")

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

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

// load custom library
calledRuntime.LoadLibrary(libraryPath)

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

// set static field's value
calledRuntimeType.SetStaticField("staticValue", 75).Execute()

// get type's static field
response, _ := calledRuntimeType.GetStaticField("staticValue").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 JAR library, and next retrieves reference to specific type, then sets and gets the static field. Result of the invocation is returned as regular GoLang value and can be used for further processing.

Get/Set static field from standard JAR library in GoLang

The same steps are required to get types and fields from framework JAR library:

// use Activate only once in your app
Javonet.ActivateWithCredentials("your-license-key")

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

// get type from the runtime
calledRuntimeType, _ := calledRuntime.GetType("java.lang.Math").Execute()

// get type's static field
response, _ := calledRuntimeType.GetStaticField("PI").Execute()

// get value from response
result := response.GetValue().(float64)

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

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 JAR library 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.