Using Java in JavaScript Adapters

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Overview

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


UsingJavainJS

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 Calculator.java.

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].

Last modified on January 16, 2017