Understanding Good Code Structure: Models, Utils, Services, DAO, and Controllers

Target audience: Junior developers with less than two years of experience and complete beginners.

Outline: Why a good code structure is needed, what constitutes a good structure, the meaning of each layer, applicability to Web, Android, and iOS, and whether further study should move toward system architecture.

1. Why a good code structure is needed

It helps decompose and re‑assemble a system, making the code easier to understand.

It reduces friction during code hand‑over and prevents chaotic situations.

It enables smoother multi‑person collaboration without endless disputes.

Bad code is often described with vivid metaphors such as “a pile of poop” or “a tangled ball of yarn,” emphasizing the confusion and difficulty of working with it.

2. What a good structure looks like

Single responsibility – each component does one thing.

Generality – components can be reused across contexts.

Clear definition – interfaces and contracts are well specified.

Frameworks (e.g., Java, Android, iOS, and later JavaScript libraries) provide scaffolding that enforces these principles.

3. Meaning of each layer

Model – pure data objects (e.g., Article, Comment) that map directly to persistence stores like MySQL or MongoDB.

Util – utility classes that perform generic data processing unrelated to business logic; they should be public, testable, and replace private helper methods.

Service – encapsulates business operations, may orchestrate multiple Utils or other Services, and defines a clear contract (e.g., “what you need, ask me”).

DAO – data‑access objects responsible solely for CRUD operations against the database; each Service should ideally correspond to one DAO.

Controller – the entry point that dispatches requests to Services, often the source of “dirty code” if business logic leaks into it.

4. Applicability to Web, Android, and iOS

Java back‑ends already have clear layered structures. Android follows a similar pattern (MVP/MVC). iOS lacks an official framework, leading to ad‑hoc data handling, but utilities exist. The Web (JavaScript) historically mixed HTML/CSS/JS, but modern frameworks like Angular, React, and Vue introduce clearer architectures.

5. Further learning

Beyond the basics, one should study system architecture, service design, decoupling, inter‑service communication, message queues, and databases such as MongoDB.

All the above content is intended for engineers with less than two years of experience.

Source: zhihu.com/question/58410621/answer/156868800