Rowanto Luo


Just another blog. or log.


  1. JavaScript, beware of filling an array with empty array.

    I love JavaScript, however very often, it doesn't love me back. const dataBuffers = new Array(4); dataBuffers.fill([]); for (let i = 0; i < 4; i += 1) { dataBuffers[i].push(7); } console.log(JSON.stringify(dataBuffers)); // guess what is the answer? If you guess the answer would be [[7],[7]…

    on javascript, array, empty array, fill array with empty array

  2. Adding New Currency in Java 8

    If you are using the java.lang.Currency as part of your entity, most likely you are already regretting it now. Most of the time, a currency is a three letter word, and we don't need the logic to be bundled in there. Keeping things simple and mapping these currencies…

    on byr, byn, java currency, java multi currency, java, currency data format is incorrect, error, elasticbeanstalk, ec2, patch java

  3. To Lead, and to Serve

    Around last week, I was listening to Rev. Stephen Tong's Masterclass (basically like a Seminar). He said something which really struck me deeply. It's something along this line: Woe to you who wants to become a leader because you want people to serve you! Woe to you if you want…


  4. Event Driven Architecture

    Why do we need it? In the early stages of the development, event driven architecture is not needed since everything is still small and could still be contained in one place. Unfortunately, as the system grows bigger and bigger, putting everything in one place is not a very good way…

    on java, programming, eda, event driven architecture, stream, event, tech

  5. Spring Boot Actuator + Dropwizard + Cloudwatch

    Exporting spring boot metrics to cloudwatch may not be that straightforward. Since I've done that for my project, I will show how we can do it easily with the help of a couple of libraries. First, spring boot is using its own metrics mechanism. The first step to do that…

    on spring boot, spring actuator, actuator, dropwizard, metrics, cloudwatch, dropwizard metrics, aws