sdc-calling-custom-java-from-jython

Overview

This project provides an example of creating and packaging a custom Java class within a jar file, loading the jar file into an SDC Jython Evaluator, and calling both static and instance methods on the class from the Jython script.

Requirements

• Maven is needed to compile the Java class and to package it in a Jar file

• SDC with the Jython stage library

Inspect the Java source file

The Java source file is a trivial class with one instance method and one static method:

package com.onefoursix;

public class Doubler {

  public long double_it_instance_method(int x){
   return 2 * x;
  }
  
  public static long double_it_static_method(int x){
    return 2 * x;
  }
}

Build the Java project

• Clone this project to your local machine.

• Switch to the java directory and execute the command

    $ ./build.sh
  

  That will generate the file doubler.jar

Import the example pipeline

Import the project's pipeline CallingJavaFromJython.json into SDC. The pipeline looks like this:

The Dev Raw Data Source generates a single record with the field x with a value of 7

Import the jar file into the Jython stage

Import the doubler.jar file into the Jython stage:

Inspect the Jython script

The Jython script has this Jython code that imports the com.onefoursix.Doubler class from the jar, calls a static method on the class, then creates an instance of the class and calls a method on the instance.

Here is the Jython code:

# Import the Java class from the jar file
from com.onefoursix import Doubler

for record in sdc.records:
  try:
    
    # Read an int field from a record
    x = record.value['x']
    
    # Call a static method on the Java class to double the record field value
    record.value['doubled_by_static_method'] = Doubler.double_it_static_method(x)
    
    # Create an instance of the Doubler class
    d = Doubler()
    
    # Call a method on the instance to double the record field value
    record.value['doubled_by_instance_method'] = d.double_it_instance_method(x)
    
    sdc.output.write(record)
  except Exception as e:
    sdc.error.write(record, str(e))

Preview the pipeline to see it working