Blog

Coverage with Jacoco and Sonarqube

In most projects I have worked in, Jacoco was used as tool to determine code coverage. The configuration is fairly easy as it plugs into the JVM that runs the tests using an agent that tracks the invocations. In maven, this JVM is forked by the surefire plugin and the parameters are auto generated. The setup is well documented so in this blog post I want to shed some lights on the internals of Jacoco and Sonarqube and how both calculate their coverage metrics. I did some code digging, and I’d like to share my insights. The following information is a compilation of what I found out.

This article is inspired by this question on StackOverflow, which is basically about how Sonarqube and Jacoco calculate coverage.

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How to write good code

A couple of days ago I stumbled over a tweet on Twitter. It contained a list of catchy phrases what makes good writing. Developers also write, but more code than prose texts, so I wondered how applicable this list is to coding as well. So I came up with my own list, which might be a bit less catchy but is hopefully a usefully assembly of good coding practices or guiding principles.

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Light Bulb Methods

While writing the article on “How to write good code”, I used the term “light bulb methods” and I want to explain bit more in detail, what I meant with this style of method structuring.

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Optimizing Docker Images for Java

Docker is a popular technology for creating runtime environments for servers and entire systems. Docker images are easily distributed, deployed and started. But especially distribution benefits from slim images - large images take time to transmit, especially when done frequently this could have a real impact on the development speed. In this article I’ll write about some best practices for reducing or optimizing the image size.

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Cognito based authentication for CloudFront protected resources

Cognito is a relatively new offering proving Identity Management for Apps and Services, including profile management and multi-factor authentication. CloudFront is the Content Delivery Network service provided by Amazon Web Services. CloudFront offers publicly accessible content as well as private content. Private content can be access using either signed URLs or Signed Cookies. Cognito however generates OAuth access tokens. This article describes how to build a service for creating Signed Cookies for Cloudfroint using access control provided by Cognito.

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Modular Router Design for Vert.x Microservices

When developing micro services with the Vert.x framework I stumbled more than once over the question how to organize Verticles and achieve a modular design. Vert.x is unopinionated allowing various ways of accomplishing this. In this article I’d like to discuss two options for building modular services.

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Integration Testing of Microservices, Part 1

Integration Testing is the second-most important phase in Continuous Integration and Delivery. It’s the first time, multiple components interact with each other. The current trend towards microservice software-architectures require a new thinking regarding integration testing of distributed systems. In this article I want to reflect on the challenges for testing those architectures. In monolithic applications, components or parts are tightly bundled. Incompatibilities can often be detected already during compilation. Components interact with each other through messages that are transmitted locally, i.

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Coding Style for high productivity and lesser bugs

In this year’s JCrete unconference I attended a very interesting session about Bugs and Coding style led by Cliff Click (The full discussion can be found here). He started about his experience as a high-performance high-professional coder, about development speed and ratios of bugs in new code, refactored code and bug-fixed code and the implication of this to the code style. Speed of Coding and Rate of Bugs His views and experience are especially interesting as he wrote huge parts of the HotSpot JVM, i.

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Building Low-Cost IoT with NodeMCU and Vertx MQTT

On this year’s JCrete conference I learned during the hackday about the NodeMCU board, which is an impressive low-cost alternative to an Arduino. It uses the 80 MHz ESP8266 chip that includes WiFi support out of the box. In this article I’d like to describe how to make a simple temperature and pressure sensor device that publishes data via MQTT to a handler implemented using the reactive Vert.x framework. The hardware for the solution costs no more than $15.

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