Working with n-D arrays from JAR library in Python

This article provides an introduction to cross-technology handling of multidimensional arrays. Data structures are one of the essential aspects of every piece of software. Any application constantly process various information, that very often require specific grouping and access strategies. This aspect is addressed by arrays and more advanced collection types. By using the Javonet framework, users gain ability to easily and effectively work with data structures originating from JAR library. Every array from JAR library is treated as reference.

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.
ith Javonet you can interact with arrays from JAR library like they were available in Python but invocation must be performed through Javonet SDK API.

Custom JAR library with arrays handling

With Javonet it is possible to reference any custom JAR library and interact with arrays declared on types defined within that module almost the same as with any other Python library.

Snippet below represents the sample code from JAR library 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 = 0.0;
	for (Double value : myArray) {
		sum += value;
	}
	return sum * myValue;
}

Javonet SDK contains various methods to interact with arrays and consume the results in Python:

Get element of 2D array from JAR library in Python

# use activate only once in your app
Javonet.activate("your-license-key")

# create called runtime context
called_runtime = Javonet.in_memory().jvm()

# set up variables
library_path = resources_directory + '/TestClass.jar'
class_name = 'TestClass'

# load custom library
called_runtime.load_library(library_path)

# get type from the runtime
called_runtime_type = called_runtime.get_type(class_name).execute()

# create type's instance
instance = called_runtime_type.create_instance().execute()

# invoke instance's method
array = instance.invoke_instance_method("get2DArray").execute()

# three ways to get elements from array
response1 = array.get_index(0, 0).execute()
response2 = array.get_index([0, 1]).execute()
response3 = array[1][1].execute()

# get value from response
result1 = response1.get_value()
result2 = response2.get_value()
result3 = response3.get_value()

# write result to console
print(result1)
print(result2)
print(result3)

In the snippet above, get2DArray method is used to get reference to 2D array from JAR library. Method getIndex is used to get element from the array. Depending on calling technology there is one or more ways to get element from array.

Set element of 2D array from JAR library in Python

# use activate only once in your app
Javonet.activate("your-license-key")

# create called runtime context
called_runtime = Javonet.in_memory().jvm()

# set up variables
library_path = resources_directory + '/TestClass.jar'
class_name = 'TestClass'

# load custom libraries
called_runtime.load_library(library_path)

# get type from the runtime
called_runtime_type = called_runtime.get_type(class_name).execute()

# create type's instance
instance = called_runtime_type.create_instance().execute()

# invoke instance's method
array = instance.invoke_instance_method("get2DArray").execute()

# two ways of setting elements in array
array.set_index([1, 1], "new value 1").execute()
array[0][1] = "new value 2"

# two ways of getting elements from array
response1 = array.get_index(1, 1).execute()
response2 = array[0][1].execute()

# get value from response
result1 = response1.get_value()
result2 = response2.get_value()

# write result to console
print(result1)
print(result2)

In the snippet above, get2DArray method is used to get reference to 2D array from JAR library. Method setIndex is used to set element of the array.

Get size and rank of 2D array

# use activate only once in your app
Javonet.activate("your-license-key")

# create called runtime context
called_runtime = Javonet.in_memory().jvm()

# set up variables
library_path = resources_directory + '/TestClass.jar'
class_name = 'TestClass'

# load custom libraries
called_runtime.load_library(library_path)

# get type from the runtime
called_runtime_type = called_runtime.get_type(class_name).execute()

# create type's instance
instance = called_runtime_type.create_instance().execute()

# invoke instance's method
array = instance.invoke_instance_method("get2DArray").execute()

# get array's size and rank
response1 = array.get_size().execute()
response2 = array.get_rank().execute()

# get value from response
result1 = response1.get_value()
result2 = response2.get_value()

# write result to console
print(result1)
print(result2)

In the snippet above, get2DArray method is used to get reference to 2D array from JAR library. Method getSize is used to get number of elements of the array.
Method getRank is used to get number of dimensions of the array.

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.