When looking at problems, your mind becomes consumed with how to force everything into design patterns—like architectural separation, DI, or interface / implementation split. This causes developers to lose sight of the actual essence of the problem because they are obsessed with conforming to the framework.

Because the ecosystem and toolchain surrounding Spring Boot and Java are so mature and well-supported, it is very easy to find community tools that make you feel like you are doing things the "right way."

I only realized these issues after I left Spring Boot and Java development behind. Now, I much prefer using TypeScript or Python to write code (for example, web servers).

I also prefer using various SaaS solutions to handle authentication and user registration rather than rebuilding it all myself with Spring Boot Security. I honestly never want to go back to the days of writing Java again.

Dependency injection is good. It makes it possible to test stuff.

Automagic wiring of dependencies based on annotations is bad and horrible.

If you want to do dependency injection, you should do it the way Go programs do it. Create the types you need in your main method and pass them into the constructors that need them.

When you write tests and you want to inject something else, then create something else and pass that in.

But the idea that you create magic containers and then decorate packages or classes or methods or fields somewhere and then stuff suddenly gets wired into something else via reflection magic is a maintenance nightmare. This is particularly true when some bean is missing, and the one guy who knows which random package out of hundreds has that bean in it is on vacation and the poor schmucks on his team have no clue why their stuff doesn't work.

"I added Spring Boot to our messy Java project."

"Now you have 3 problems."

I expected to see some new Spring 'tricks' in this post, but it's pretty much regular things that people might do in larger codebases.

- Go for declarative Kotlin DSLs over annotation magic for most things. Much easier to debug. It's just function calls. And DSLs are nice in IDEs with autocomplete.

- Keep it simple. It's a huge framework. But you probably don't need most of it.

- Don't go Spring everything, a lot of stuff in Spring is a bit experimental (Spring AI/MCP stuff) or a bit bare bones (Spring Data, it's a limited and extra level of indirection you mostly shouldn't need) or flat out misguided/over-engineered (Spring Batch, good alternatives are available for that).

- Decide on synchronous or asynchronous IO. The former is a lot more scalable now that Java has green threads. The latter is relatively painless from Kotlin but an absolute PITA from Java. They are very different internally and both have their pros/cons. If you need async, Kotlin co-routines is the easier path to do that. Either way, it's one of the bigger decisions to take.

- Don't copy their way of deeply nested inheritance hierarchies. Very much in fashion 20 years ago; a bit of an anti pattern now. Internal code complexity is the part I like least about Spring. And it has some really byzantine stuff in there with 5-6 levels of inheritance or worse.

These kinds of infrastructure systems its very common to replace a bunch of the built in functionality with your own classes, and so there's alot of effort put into supporting that use case.

I helped build a large open source enterprise financial systems, and most of the deploying orgs used CAS for authN. Both CAS and the financial system was built with similar approach to extensibility.

I think this is the main point. You can write good code in any language following this concept.

Just rewrote it in Go. Now we are using a server which consumes 30% of ram what the existing one used to and the latency and throughput have all improved.

Don't use these stupid java backend like sprinboot.