Using Java in JavaScript Adapters

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When JavaScript is not sufficient to implement required functionality, or if a Java class already exists, you can use Java code as an extension for the JavaScript adapter.

Prerequisite: Make sure to read the JavaScript Adapters tutorial first.

Adding custom Java classes


To use an existing Java library, add the JAR file as a dependency to your project. For more information on how to add a dependency, see the Dependencies section in the Creating Java and JavaScript Adapters tutorial.

To add custom Java code to your project, add a folder named java to the src/main folder in your adapter project and put your package in it. The sample in this tutorial uses a com.sample.customcode package and a Java class file named

Important: The package name must start with either com, org, or net.

Add methods to your Java class.
Here are an examples of a static method (that does not require a new instance) and an instance method:

public class Calculator {

  // Add two integers.
  public static int addTwoIntegers(int first, int second){
    return first + second;

  // Subtract two integers.
  public int subtractTwoIntegers(int first, int second){
    return first - second;

Invoking custom Java classes from the adapter

After your custom Java code is created and any required JAR files are added, you can call it from the JavaScript code:

  • Invoke the static Java method as shown, and use the full class name to reference it directly:
function addTwoIntegers(a,b){
    return {
        result: com.sample.customcode.Calculator.addTwoIntegers(a,b)
  • To use the instance method, create a class instance and invoke the instance method from it:
function subtractTwoIntegers(a,b){
    var calcInstance = new com.sample.customcode.Calculator();   
    return {
        result : calcInstance.subtractTwoIntegers(a,b)

Sample adapter

Click to download the Maven project.

Sample usage

When testing, the adapter expects an array with numbers to add or subtract, for example: [1,2].

Inclusive terminology note: The Mobile First Platform team is making changes to support the IBM® initiative to replace racially biased and other discriminatory language in our code and content with more inclusive language. While IBM values the use of inclusive language, terms that are outside of IBM's direct influence are sometimes required for the sake of maintaining user understanding. As other industry leaders join IBM in embracing the use of inclusive language, IBM will continue to update the documentation to reflect those changes.
Last modified on January 10, 2017