Adding Spring Security to an existing application can be quite a daunting prospect. Merely adding the required dependencies to your project sets off a chain of events which can break your application and tests.

In a previous post I’ve shown how to use ZIO environments to provide your program with dependencies, or modules. While using environments at the customer I’m currently working for, we found out that the logic to get a database session object using a module would run over and again. This makes sense, since a ZIO[R, E, A] is a prescribed way of getting an A, and the result is not cached. Our application was reading configuration files and creating SQL sessions on every module call, while the resulting object was obviously constructed from the same underlying values. There are multiple ways to solve this:

When combined with Spring Security 5.2+ and an OpenID Provider such as Keycloak, one can rapidly setup and secure Spring Cloud Gateway for OAuth2 resource servers.

This is an overview of some optimization techniques used by Hotspot JVM to increase performance. I will start by giving a small example of how I ran into these optimizations while writing a naive benchmark. Each optimization is then explained with a short example and ends with some pointers on how to analyze your own code.

You might have a need for a custom access decision voter when security decisions are made based on who is accessing what domain object. Luckily Spring Security has quite a few options for such implement such access control list (ACL) constraints.

ZIO is a type-safe, composable library for asynchronous and concurrent programming in Scala (from: The ZIO github). The library copes with functional IO, like many Functional Programming libraries do. The added value of ZIO is that the ZIO[R, E, A] type-constructor (the main IO monad of the library) acts as an IO monad, an error handling monad, and a reader monad. A functional programming style often needs a combination of these three types to cope with the most common problems when creating an application:

Often you’ll find access decisions move beyond simplistic ownership or having a certain role, for instance when users share domain objects with other users. In such cases it’s common to separate permission to view an instance from being able to make changes to the same instance. When your access rules are relatively straightforward, Spring Security offers the PermissionEvaluator interface to secure instance access.

ZIO is a type-safe, composable library for asynchronous and concurrent programming in Scala (from: The ZIO github). The ZIO framework provides your program as immutable and pure values, which are very simple to properly unit test. But how can you run an integration test to see if your application starts up properly?

Spring Data repositories allow you to easily query your entities with method names such as findByUserName(String name). However, it can get cumbersome to always retrieve, pass and match on the active user. Luckily Spring Security integrates well with Spring Data to minimize the overhead.

Spring Data enables you track who modified an entity and when, with just a few annotations. When combined with Spring Security, you can set this metadata based on the active user.

Distributed tracing is a method used to profile and monitor applications, especially those built using a microservices architecture. Distributed tracing helps pinpoint where failures occur and what causes poor performance.^[1] Applied to Kafka Streams it allows us to trace and visualize our messages by propagating diagnostic information within message headers.

Using the Stream API and the map method we can transform elements in a stream to another object. Instead of using the map method we can also write a custom Collector and transform the elements when we use the collect method as terminal operation of the stream.