Common Code Smells in Spring Applications — How to Fix Them

Ramesh Fadatare

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4 min read

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Apr 22, 2025

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Writing clean, maintainable Spring code isn’t just about annotations and configuration — it’s about structure, clarity, and avoiding hidden traps that slow down your team over time.

In this article, we’ll explore the most common code smells in Spring applications, explain why they’re a problem, and show you how to fix them — the right way.

🚫 1. Fat Controllers

🔍 What’s the smell?

Your controller has too much logic — business rules, validation, repository calls — all in one place.

@RestController
public class OrderController {

    @PostMapping("/orders")
    public String placeOrder(@RequestBody Order order) {
        if (order.getAmount() <= 0) {
            return "Invalid order";
        }
        orderRepository.save(order);
        notificationService.notify(order);
        return "Order placed";
    }
}

❌ Why it’s bad:

• Hard to test
• Breaks Single Responsibility Principle
• Becomes a god class over time

✅ Refactor: