Coveralls is web service created by LEMUR Heavy that helps tracking code coverage over time. Coveralls is free to use for open source projects and it requires that the projects are hosted at GitHub. The service was originally created for Ruby projects, but the provided API allows anybody to create code coverage report clients. Numerous integrations have been created for different languages such as Python, PHP, Node.js and Scala by the open source community, but there was no support for Java projects. I find this odd, because in the enterprise Java world such metrics are everyday life. There are plenty of different coverage tools and metrics platforms available like Cobertura, JaCoCo, SonarQube (previously known as Sonar) and so on. Continue reading


Recently an encoding issue of HTTP form POST requests with Tomcat was found in a project I work. The form submit was triggered with Javascript and the normal submit behavior was disabled. The form page was rendered with Content-Type: text/html; charset=UTF-8 header, the HTML head section had <meta charset="utf-8"> hint and the form was defined as normal <form> without any additional attributes. This should have resulted the form to posted with application/x-www-form-urlencoded content type using UTF-8 encoding. But no, this did not work with Tomcat, for unknown reason, though everything worked fine with Jetty application server. Continue reading



Java Comparable interface provides a way to do natural ordering for classes implementing the interface. Natural ordering makes sense for scalars and other quite simple objects, but when we come to more business oriented domain objects the natural ordering becomes much more complicated. A transaction object’s natural ordering from business manager’s point of view could be the value of the transaction, but from the system admin’s point of view the natural ordering could be the speed of the transaction. In most cases, there is no clear natural ordering for business domain objects. Continue reading


One of the core concepts of Apache Wicket web framework is the model and IModel as its programming interface. Wicket components rely heavily on models, which makes them important pieces of the architecture. Apache Wicket is stateful framework that stores the pages and their components to a page store that usually resides in the HTTP session. Components create the public facing view from the content of the models. Misusing models can cause awkward side effects, like pages not updating their content or huge memory consumption in your application. And the most issues with new Wicket users, from what I’ve seen, are with the correct use of the models. In this blog post I’ll try to explain how and what kind of models should be used in different use cases. Continue reading