Category Archives: Programming

Progress Bar implementation in Java for Terminal application

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Th e”\r” character basically reverts the current cursor back to the 1st column in the current line. This concept should basically work on Mac, Linux and Windows. So to test it I wrote a quick hack and it worked properly:

public class ProgressBar {

    public static void main(String[] args) {
        int size = 10;
        for (int i=1; i<size; i++) {
            try {
                Thread.sleep(500);
                System.out.print("|" + "=".repeat(i) + ">" + " ".repeat(size-i) + "|\r");
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        System.out.print("|" + "=".repeat(size) + "|\r");
    }
}

// Initial Output
// |=>        |
// Final Output
// |==========|

I got the desired output and a humble do nothing progress bar did come up on terminal. To further this idea I did some internet search and I ended up finding this repo on GitHub. It basically allows you to implement beautiful progress bars for terminal based Java application. The basic concept is the same but it provides much more functionality.

Spring Cloud Configuration Issue

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For a new project I was trying to setup a config server to connect my services together. Although the spring-cloud-config server works fine, I am not able to make my service talk to the config-server which is really strange as I am fairly well versed with Spring Cloud and usually setting up a dev environment is a no-brainer.

I have described my issue in stackoverflow to get help and I am debugging in parallel as well.

Bye Bye Hystrix

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Hystrix used to be my tool of choice for implementing circuit breakers in my Spring Boot application. However there has been literally no commits in Hystrix github repo for past 1 year. It seems Netflix has moved on to resilience4j which will be actively maintained.

Resilience4j commit log is quite active and a lot of active work is going on in it.

However it should be noted that there is another mature library named Sentinel which seems to be quite feature rich and very well supported. It has been battle tested by Alibaba which is huge. In my next project I would be considering both Sentinel and Resilience4J in my choice for a reliable circuit breaker for my application.

Taking backup zip from multi-module Java project

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I like to keep an archive of my code on a monthly basis. I wrote a small bash script to create zip out of my multi module Java projects. It gets the job done and can be improved to include resources and test folders as well. As of now I am only interested in the Java code zip backup.

!/bin/bash
 if [ -d "combined" ]; then
     echo "Removing existing zip files in combined .."
     rm combined/*.zip
 else
     echo "Creating combined folder.."
     mkdir combined
 fi
 for d in */ ; do
     if [ -d "$d/src/main/java" ]; then
         var="$(echo $d | sed 's/.$//')"
         echo "Processing $var .."
         cd $d/src/main/java
         zip -r ../../../../combined/$var.zip com
         cd ../../../..
     else
         echo "Ignoring .. $d"
     fi
 done

Triggering download of file using JavaScript

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I recently needed to write a small piece of download code. So you pass in the ID of the document to a REST API and it should give you back a blob of the actual file. The problem however is how to actually save this blob of binary data into a local file. So a quick Googling threw up some interesting links which I finally used to finalize my solution.

Code to detect file name

Code to trigger download