Recursive loop in Talend

Author : Girish Mallula

Introduction

It is great challenge for Java developer who wanted to implement some the concepts like “Recursive Looping” which exist in Java.

Recursive looping is one of the topic which is hard to replicate in Talend but it is not impossible.

Recursive Loop

The process in which a function calls itself directly or indirectly is called recursion and the corresponding method is called as recursive method. For example lets take “Factorial of a Number Using Recursion Loop”

class Fact {

    static int fact( int n ) {
        if (n != 0)  // Loop breaking condition
            return n * fact(n-1); // recursive loop
        else
            return 1;
    }

    public static void main(String[] args) {
        int num = 5;
        int value = fact(num);
        System.out.println(num + " factorial = " + value);
    }
}

Let’s start in Talend Studio

1. Let me start with a practical user case to demonstrate recursive looping in Talend. So, let’s take a simple usescase where we need retrieve all the files which exists in root folder and its sub directories without using tFileList sub directories option.

2. So here is folder structure there is root directory and under there are multiple folders and files.

3. Initially I am storing my root directory location in a temp file. And this temp file acts as “Parameter Value” for my functionality.

4. And I am using tLoop component to iterate though my functionality.

5. Here I am using “isLoopBreaker” context variable to break my loop. This variable is sent be true when there is no sub folder found in the root directory.

6. List of main compounds and their purposes:

• tLoop -> to the loop thought the flow of compounds
• tFileInputDelimeter -> to retrieve folder details which are stored in temp file
• tFlowToIterate -> to loop thought all the sub folders
• tFileList -> to get properties of all files and folders
• tMap -> it is used to split flow of folders and files details
• tFileOutputDelimeter -> to store folder details in the temp file
• tHashMap -> to store in the details of files in hash map

7. And you will get list of files from tHashOutput.

8. In the result, tLogRow_3 will print list of folder at each level. And tLogRow_2 will print list of files.

9. Happy Learning !!