🤖 AI Code Agent: Login System

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This project demonstrates how I used an AI code agent to design and implement a secure login system.

🎯 Task

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Build a login system using:

• Java
• Javalin
• Hibernate
• JWT authentication

⚙️ Features

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• User registration
• Secure login
• Password hashing (BCrypt)
• JWT authentication
• Protected routes

🔄 Workflow with AI

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1. Architecture design

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I started by prompting the AI:

“Create a login system using Javalin, Hibernate and JWT”

The AI suggested a layered architecture:

• Controller
• Service
• DAO
• JWT Utility

2. Initial implementation

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The AI generated:

• Register endpoint
• Login endpoint
• JWT token generation

However, the initial solution had issues:

• Missing validation
• Weak error handling
• No route protection

3. Debugging

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I collaborated with the AI to fix:

• Hibernate mapping issues
• Null pointer errors
• Incorrect JWT configuration

4. Refactoring

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The AI helped improve:

• Separation of concerns
• Code readability
• Naming conventions

5. Security improvements

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We added:

• BCrypt password hashing
• JWT middleware
• Token validation

Key Learnings

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• AI is effective for scaffolding backend systems
• Debugging requires human understanding
• Security must be validated manually
• Iteration improves output quality

Example flow

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User registers → Password hashed → Stored in DB
User logs in → JWT generated → Used for protected routes

Conclusion

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AI code agents can significantly speed up backend development, but require:

• Critical thinking
• Validation
• Security awareness

They are best used as collaborative tools rather than replacements.