Toggable Cache


Sometimes it’s good to have an option to try something out on the live environment. Checking things against production like traffic is the most reliable way to gather real-life metrics. In this post, I’m going to try and set up spring cache with a toggle. It’ll be possible to turn it off and on during application runtime possibly using external toggle service.

9 Jan 2020

Use replica database for read-only transactions


Some time ago we had a problem with performance caused by generating big reports for users. During one of the firehouse meetings, there was an idea to generate reports from the replica database. We’ve solved the issue differently but the idea got me interested. In this post, I’ll configure spring-boot based application to use the replica database for all read-only transactions.

27 Nov 2019

Error handling with @Transactional


You probably already know that by default in spring transactions are rolled back only for runtime exceptions. When a checked exception is thrown from your code and you don’t explicitly tell spring that it should rollback the transaction then it get’s committed. In this post, I’m going to create simple reference material on when transactions are rollback when using Spring and Lombok.

11 Nov 2019

ProxyFactory and ProxyFactoryBean in Spring


Spring provides many easy to use abstractions and you use many of them without even knowing about them. You probably know that in order to have @Transactional or @Cacheable annotation work spring creates proxies for you (sometimes proxies on top of proxies…​), but have you ever wondered how it’s happening under the hood? What Creation of object proxies is a cumbersome task. One has to decide if the proxy should be created using native java mechanisms (JdkProxy available only on interfaces) or using cglib and it’s complicated interfaces.

13 Jun 2019

Spring internals - BeanDefinition


How beans are registered in spring and what is the base of beans creation, how to extend spring’s context to our needs? In this post, I’m going to dig into the foundation of many mechanics in spring framework - bean definition.

29 Apr 2019

Spring's properties misconfiguration dangers


Some time ago I’ve faced a very interesting support issue. Long story short it turned out that one of our applications was not connecting to proper service and as a result, it’s been displaying invalid data to users. After a bit of investigation, I’ve noticed that spring’s configuration mechanism did fallback to default value because of missing configuration key for the production profile. In this post, I’m going to present to you how we are going to avoid similar issues in the future.

11 Apr 2019



Have you ever wondered how it’s possible that spring-boot is able to pick up whatever you have on the classpath and configure application context to your needs based on some conventions and bit of black magic? In this post, I’m going to dig into spring.factories file on which most of the spring-boot power is based.

28 Mar 2019

Spring internals - BeanPostProcessor


Have you ever wondered how spring does things? How field annotated with @Autowired is populated? How asynchronous or scheduled methods are discovered. In this post, I’m going to take a deeper look and scratch a bit on the surface of spring internals. I’ll focus on BeanPostProcessor interface which can be used to achieve interesting things and is used in many various functionalities across spring framework itself.

20 Feb 2019

Testing MVC in Spring


Most of java web applications is built on top of the Spring Framework. Spring has pretty good support for testing and it is a mistake not to take advantage of features it offers. I’ve been developing various applications using Spring MVC for some time and I’ve noticed few patterns for testing that do work.

30 Jan 2018