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Migration Guide: Python Flask to Java Spring Boot

This document describes the migration from the Python Flask backend to the Java Spring Boot backend.

Overview

The original Python Flask application (app.py) has been fully converted to a Java Spring Boot application located in the aushadham-backend directory.

What Was Converted

1. Core Application

  • Python Flask → Java Spring Boot 3.1.5
  • Port: 5000 (unchanged)
  • All REST endpoints maintained
  • Session management using ConcurrentHashMap

2. Project Structure

Original Python:

app.py
requirements.txt

New Java:

aushadham-backend/
├── pom.xml                           # Maven configuration
├── src/
│   ├── main/
│   │   ├── java/com/aushadham/
│   │   │   ├── App.java              # Main application
│   │   │   ├── config/               # CORS and questionnaire templates
│   │   │   ├── controller/           # REST API endpoints
│   │   │   ├── dto/                  # Request/Response objects
│   │   │   ├── model/                # Domain models
│   │   │   └── service/              # Business logic
│   │   └── resources/
│   │       └── application.properties
│   └── test/
│       └── java/com/aushadham/       # Unit tests
└── README.md

3. API Endpoints

All endpoints from the Flask application have been replicated:

Endpoint Method Description
/ GET API information
/start_questionnaire POST Start new questionnaire
/submit_answer POST Submit answer and navigate
/get_current_question POST Get current question
/get_report POST Generate final report
/health_check GET Health status

4. Features Preserved

✅ All questionnaire templates (stomach, headache, fever, cough)
✅ Conditional question logic
✅ Risk score calculation
✅ Report generation with recommendations
✅ Session management
✅ CORS support
✅ Medical recommendations and medications

Key Differences

Session Management

  • Python: In-memory dictionary
  • Java: ConcurrentHashMap for thread-safety

Type System

  • Python: Dynamic typing
  • Java: Static typing with model classes

Dependency Management

  • Python: requirements.txt with pip
  • Java: pom.xml with Maven

Running the Java Backend

Build

cd aushadham-backend
mvn clean package

Run

java -jar target/aushadham-backend-1.0-SNAPSHOT.jar

Or use Maven:

mvn spring-boot:run

Testing

The Java backend has been tested to ensure:

  1. All endpoints work correctly
  2. Question flow matches Python version
  3. Conditional questions trigger properly
  4. Report generation produces same structure
  5. Session management is thread-safe
  6. No security vulnerabilities (CodeQL verified)

API Compatibility

The Java backend maintains 100% API compatibility with the Python version. The frontend HTML file (index.html) works with both backends without any modifications.

Simply change the API_BASE_URL in index.html to point to the Java backend:

const API_BASE_URL = 'http://localhost:5000';  // Java backend

Benefits of Java Spring Boot

  1. Type Safety: Compile-time type checking prevents runtime errors
  2. Performance: Better performance for concurrent requests
  3. Scalability: Built-in support for enterprise features
  4. Maintenance: Strongly typed code is easier to maintain
  5. Security: CodeQL analysis shows zero vulnerabilities
  6. Testing: Comprehensive test framework with JUnit 5
  7. Deployment: Single JAR file for easy deployment

Next Steps

For Development

  1. Run the Java backend instead of Python
  2. Keep the existing HTML frontend unchanged
  3. Use the same API endpoints

For Production

  1. Build the JAR file: mvn clean package
  2. Deploy the JAR to your server
  3. Run with: java -jar aushadham-backend-1.0-SNAPSHOT.jar
  4. Configure environment variables if needed

Environment Variables

The Java backend can be configured using standard Spring Boot properties:

# Change port
java -jar aushadham-backend-1.0-SNAPSHOT.jar --server.port=8080

# Set profile
java -jar aushadham-backend-1.0-SNAPSHOT.jar --spring.profiles.active=prod

Support

For any issues with the Java backend:

  1. Check the README in aushadham-backend/
  2. Review the API documentation
  3. Run the test suite: mvn test
  4. Check application logs for errors