Application specifications

Let's start by transforming this placeholder application into an application that counts words – the Hello World equivalent for big data processing frameworks. The functionality is easy to understand and not very important, as our focus here is on the development process.

The full source code of the modified application is available at https://github.com/tweise/apex-samples/tree/master/wordcount. Here is the modified application assembly in Application.java:

@Override
   public void populateDAG(DAG dag, Configuration conf)
   {
    LineByLineFileInputOperator lineReader = dag.addOperator("input",
         new LineByLineFileInputOperator());
     LineSplitter parser = dag.addOperator("parser", new LineSplitter());
     UniqueCounter counter = dag.addOperator("counter", new UniqueCounter());
     GenericFileOutputOperator<Object> output = dag.addOperator("output",
         new GenericFileOutputOperator<>());
     output.setConverter(new ToStringConverter...