There are plenty of online tutorials showing how to create database-based authentication for Spring. Some of them use SQL query to authenticate user and retrieve its roles, some use DAO… but none of them worked well for me and all of them had some major problems, even like SQL Injection. So, in this post I will explain my approach and present final solution with a database (MySQL), User and Role class and UserDetailsService implementation.

The goal is to create basic webpage with login form and signup form (which includes fields validation) that handles different roles. Then, you and me can use it as a template project.

This tutorial doesn’t include steps how to setup your IDE and build environment. We’re going straight to code, and I will try to avoid as much boilterplate as possible, so the code won’t include getters and setters. If you still write them by hand, time to learn about Lombok project (which I use here) or any other code generator.

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Everyone knows it’s important to keep dependencies up to date. The risks of not updating them are very often high: you risk losing your data or data of your customers, being part of a botnet or simply getting hacked by script kiddies replacing your frontpage with something shameful.
Not everyone knows how easy it is to keep your dependencies up to date with gradle. Both gradle and maven have plugins to check for updates in your list of dependencies.

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To be able to access two databases in SpringBoot you must define two data sources. In my case I had one database for identity details of users, like username, name, email, address etc. and second database for everything else.

You have to define one @Configuration class for each database and each class will wired its own datasource to services (like JpaRepository or CrudRepository) to defined packages.

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This topic presents who to setup kcov with cargo to get a test coverage for a cargo project, so I just assume you got kcov working in your Linux distribution and you have a project with source code and tests that you can run. I also assume you have gitlab-ci-multi-runner installed. So I will just quickly present who to configure it to use with GitLab CI to get test coverage badge in your new project.

I use my own CI runner, I’m not using shared runners or docker for it. So it’s pretty straightforward, your configuration will differ a bit.

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fn main() {
  let mut path: PathBuf = get_app_dir();
  let str_path = path.to_str().unwrap();
  if str_path.len() != 0 && path_exists(&path) {
    println!("Path {} exists", str_path);
fn get_app_dir() -> PathBuf {
    let dir: PathBuf = match env::home_dir() {
        Some(path) => PathBuf::from(path),
        None => PathBuf::from(""),
pub fn path_exists(path: &PathBuf) -> bool {
    return Path::new(&path).exists();

…that’s why we published our product on OSI-compatible license! We <3 open-source!

Well, does Microsoft/Google/Apple/Netflix/XXX really love open-source?

No, they don’t. In fact they do more to extinguish open source by fighting them with patent wars, you don’t hear about, developing DRM, you hear about when it’s too late and dropping support for some key-products on open source platforms. Skype on Linux, anyone? Google Drive client on Linux? DRM enabled by default in browsers, anyone?

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I’m working on a new Android project which I inherited. Well, I forked it because I didn’t feel welcomed to contribute to the project and I see a lot of places where improvements are needed.

First, I need to improve the codebase. Previous developers didn’t care about any Java coding guidelines from Oracle, Google, CERT or even Android. Some of the problems I have to solve now are:

  • inconsistent style
  • catch (Exception e){}
  • catch(Throwable e){}
  • ArrayList<Object> list = new ArrayList<String>()
  • complex methods – if {switch {for {if {else {}}}}
  • new Thread().start()

To quickly start clean-up and identify those problems, different static code analysis tools can be used; one of them is SonarQube.

Continue reading is a competitor of Github. It’s a service provider for git-based source code repositories that offers much more than it’s bigger brother. In this post I will try to convince you to try it out for your next project.

GitLab is not only a simple git hosting; its features impact the whole development process, the way of contributing to a project, executing and running tests, protecting source code from changes, more and more.

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My major project in Java (Android) involved image manipulation where I used JHLabs. I found there was no easy way to add JHLabs support for Android without extracting sources and manually adding them to the project. So there it is now:

It’s compatible with gradle build system, so you can easily add it to your gradle project.

To use it in your project:

  1. Go to the main folder of your application
  2. mkdir third_party
  3. Edit settings.gradle and add this line
    include 'third_party:jhlabs2'
  4. Add this line to your dependencies:
    compile project(':third_party:jhlabs2')
  5. It should be done now!

You can see it working in my project!

I saw such question on SO. There was no solution with RegEx so… I was bored I think.

public static boolean isValid(String ip) {
    boolean isvalid;
    isvalid = ip.matches(
            "(([0-9]|[0-9]{0,2}|1[0-9]*{0,2}|2[0-5][0-5]|0{0,3}).){3}" +
    return isvalid;

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