starspring 0.2.0

A Spring Boot-inspired Python web framework built on Starlette, combining the elegance of Spring's dependency injection with Python's simplicity

StarSpring

A Spring Boot-inspired Python web framework built on Starlette, combining the elegance of Spring's dependency injection with Python's simplicity.

Table of Contents

• What is StarSpring?
• Key Features
• Framework Comparison
• Core Concepts
• Installation
• Quick Start
• Database & ORM
• Building REST APIs
• Working with Templates
• Middleware
• Advanced Features
• Examples
• Contributing
• License

---

What is StarSpring?

StarSpring is a modern Python web framework that brings Spring Boot's proven architectural patterns to the Python ecosystem. It provides:

• Dependency Injection: Automatic component scanning and dependency resolution
• Declarative Programming: Annotations-based routing, services, and repositories
• Built-in ORM: SQLAlchemy integration with Spring Data-style repositories
• Convention over Configuration: Auto-configuration with sensible defaults
• Production-Ready: Built on Starlette for high performance and ASGI support

StarSpring is ideal for developers who appreciate Spring Boot's structure but prefer Python's ecosystem, or Python developers looking for a more opinionated, enterprise-ready framework.

---

What's New in v0.2.0 🎉

Automatic Form Data Parsing

HTML forms are now automatically parsed into Pydantic models - no more manual await request.form()!

@PostMapping("/users")
async def create_user(self, form: UserCreateForm):  # Automatic parsing!
    user = await self.user_service.create(form.name, form.email, form.age)
    return ModelAndView("success.html", {"user": user}, status_code=201)

Custom HTTP Status Codes

Set custom status codes for template responses:

return ModelAndView("users/created.html", {"user": user}, status_code=201)
return ModelAndView("errors/404.html", {"message": "Not found"}, status_code=404)

HTTP Method Override

Use PUT, PATCH, and DELETE methods in HTML forms with the _method field:

<form action="/users/{{ user.id }}" method="POST">
    <input type="hidden" name="_method" value="PUT">
    <!-- form fields -->
</form>

@PutMapping("/users/{id}")  # Works with HTML forms!
async def update_user(self, id: int, form: UserForm):
    # Handles both API requests and form submissions

---

Key Features

Dependency Injection & IoC Container

Automatic component scanning, registration, and dependency resolution with constructor injection.

Declarative Routing

Define REST endpoints using familiar decorators like @GetMapping, @PostMapping, @PutMapping, and @DeleteMapping.

Spring Data-Style Repositories

Auto-implemented repository methods based on naming conventions:

async def find_by_username(self, username: str) -> User | None:
    pass  # Automatically implemented!

Built-in ORM

SQLAlchemy integration with automatic table creation, transaction management, and entity mapping.

Auto-Configuration

Automatically loads application.yaml and scans common module names (controller, service, repository, entity).

Template Support

Jinja2 integration for server-side rendering with the @TemplateMapping decorator.

Middleware Stack

Built-in exception handling, logging, CORS support, and custom middleware capabilities.

Type Safety

Full type hint support with automatic parameter injection and validation.

---

Framework Comparison

Feature	StarSpring	FastAPI	Flask	Django
Layered Architecture	Yes	No	No	Yes
Dependency Injection	Built-in IoC	Function params	Manual/Extensions	Manual
Built-in ORM	Yes (SQLAlchemy)	No	Extension	Yes (Django ORM)
Auto-Configuration	Yes	No	No	Partial
Auto-Repositories	Yes	No	No	No
Async Support	Native (ASGI)	Native (ASGI)	Limited	Partial
Template Engine	Jinja2	Manual	Jinja2	Django Templates
Admin Interface	No	No	Extensions	Yes

When to choose StarSpring:

• You're familiar with Spring Boot and want similar patterns in Python
• Building API-first or microservice architectures
• Need strong separation of concerns (Controller/Service/Repository)
• Want automatic dependency injection and component scanning
• Prefer convention over configuration

---

Core Concepts

Application Context

The IoC (Inversion of Control) container that manages component lifecycle and dependencies.

Components

Classes decorated with @Controller, @Service, or @Repository are automatically discovered and registered.

Dependency Injection

Components are injected via constructor parameters:

@Controller("/api/users")
class UserController:
    def __init__(self, user_service: UserService):
        self.user_service = user_service

Entities

Domain models decorated with @Entity that map to database tables.

Repositories

Data access layer with auto-implemented query methods based on method names.

Services

Business logic layer, typically transactional, that orchestrates repositories.

Controllers

HTTP request handlers that define REST endpoints and return responses.

---

Installation

Requirements

• Python 3.10 or higher
• pip or uv package manager

Install from PyPI

pip install starspring

Install for Development

git clone https://github.com/DasunNethsara-04/starspring.git
cd starspring
pip install -e .

Optional Dependencies

For PostgreSQL support:

pip install psycopg2-binary
# or for async
pip install asyncpg

For MySQL support:

pip install pymysql

---

Quick Start

1. Create Project Structure

my_app/
├── entity.py
├── repository.py
├── service.py
├── controller.py
├── main.py
└── application.yaml

2. Configure Database (application.yaml)

database:
  url: "sqlite:///app.db"
  ddl-auto: "create-if-not-exists"

server:
  port: 8000
  host: "0.0.0.0"

3. Define Entity (entity.py)

from starspring import BaseEntity, Column, Entity

@Entity(table_name="users")
class User(BaseEntity):
    # BaseEntity provides: id, created_at, updated_at
    
    username = Column(type=str, unique=True, nullable=False)
    email = Column(type=str, unique=True, nullable=False)
    is_active = Column(type=bool, default=True)
    role = Column(type=str, default="USER")

4. Create Repository (repository.py)

from starspring import Repository, StarRepository
from entity import User

@Repository
class UserRepository(StarRepository[User]):
    # Auto-implemented based on method name!
    async def find_by_username(self, username: str) -> User | None:
        pass
    
    async def find_by_email(self, email: str) -> User | None:
        pass

5. Implement Service (service.py)

from starspring import Service, Transactional
from entity import User
from repository import UserRepository

@Service
class UserService:
    def __init__(self, user_repo: UserRepository):
        self.user_repo = user_repo
    
    @Transactional
    async def create_user(self, username: str, email: str) -> User:
        # Check if user exists
        existing = await self.user_repo.find_by_email(email)
        if existing:
            raise ValueError(f"User with email {email} already exists")
        
        # Create and save
        user = User(username=username, email=email)
        return await self.user_repo.save(user)
    
    async def get_user(self, username: str) -> User | None:
        return await self.user_repo.find_by_username(username)

6. Build Controller (controller.py)

from starspring import Controller, GetMapping, PostMapping, ResponseEntity
from service import UserService

@Controller("/api/users")
class UserController:
    def __init__(self, user_service: UserService):
        self.user_service = user_service
    
    @PostMapping("/register")
    async def register(self, username: str, email: str):
        try:
            user = await self.user_service.create_user(username, email)
            return ResponseEntity.created(user)
        except ValueError as e:
            return ResponseEntity.bad_request(str(e))
    
    @GetMapping("/{username}")
    async def get_user(self, username: str):
        user = await self.user_service.get_user(username)
        if user:
            return ResponseEntity.ok(user)
        return ResponseEntity.not_found()
    
    @GetMapping("")
    async def list_users(self):
        users = await self.user_service.user_repo.find_all()
        return ResponseEntity.ok(users)

7. Bootstrap Application (main.py)

from starspring import StarSpringApplication

app = StarSpringApplication(title="My User API")

if __name__ == "__main__":
    app.run()

8. Run the Application

python main.py

Your API is now running at http://localhost:8000!

Test it:

# Register a user
curl -X POST http://localhost:8000/api/users/register \
  -H "Content-Type: application/json" \
  -d '{"username": "john", "email": "[e-mail]"}'

# Get user
curl http://localhost:8000/api/users/john

# List all users
curl http://localhost:8000/api/users

---

Database & ORM

Configuration

StarSpring uses SQLAlchemy under the hood. Configure your database in application.yaml:

database:
  url: "postgresql://user:password@localhost/mydb"
  ddl-auto: "create-if-not-exists"  # Options: create, create-if-not-exists, update, none
  pool-size: 10
  max-overflow: 20

Supported databases:

• SQLite: sqlite:///app.db
• PostgreSQL: postgresql://user:pass@host/db
• MySQL: mysql://user:pass@host/db

Defining Entities

Entities are Python classes decorated with @Entity:

from datetime import datetime
from starspring import BaseEntity, Column, Entity

@Entity(table_name="posts")
class Post(BaseEntity):
    title = Column(type=str, nullable=False, length=200)
    content = Column(type=str, nullable=False)
    published = Column(type=bool, default=False)
    author_id = Column(type=int, nullable=False)
    published_at = Column(type=datetime, nullable=True)

BaseEntity provides:

• id: Auto-incrementing primary key
• created_at: Timestamp of creation
• updated_at: Timestamp of last update

Column Options

Column(
    type=str,           # Python type (str, int, bool, datetime)
    nullable=True,      # Allow NULL values
    unique=False,       # Unique constraint
    default=None,       # Default value
    length=None         # Max length for strings
)

Repository Patterns

StarSpring provides Spring Data-style repositories with auto-implemented methods:

from starspring.data.query_builder import QueryOperation

@Repository
class PostRepository(StarRepository[Post]):
    # Find by single field
    async def find_by_title(self, title: str) -> Post | None:
        pass
    
    # Find by multiple fields
    async def find_by_author_id_and_published(
        self, author_id: int, published: bool
    ) -> list[Post]:
        pass
    
    # Custom queries (manual implementation)
    async def find_recent_posts(self, limit: int = 10) -> list[Post]:
        # Implement custom logic here
        return await self._gateway.execute_query(
            "SELECT * FROM posts ORDER BY created_at DESC LIMIT :limit",
            {"limit": limit},
            Post,
            QueryOperation.FIND
        )

Auto-implemented method patterns:

• find_by_<field> - Find by single field
• find_by_<field>_and_<field> - Find by multiple fields
• count_by_<field> - Count matching records
• delete_by_<field> - Delete matching records
• exists_by_<field> - Check if exists

Built-in methods:

• save(entity) - Insert or update
• find_by_id(id) - Find by primary key
• find_all() - Get all records
• delete(entity) - Delete entity
• count() - Count all records

Transactions

Use the @Transactional decorator for automatic transaction management:

from starspring import Service, Transactional

@Service
class PostService:
    def __init__(self, post_repo: PostRepository):
        self.post_repo = post_repo
    
    @Transactional
    async def publish_post(self, post_id: int) -> Post:
        post = await self.post_repo.find_by_id(post_id)
        if not post:
            raise ValueError("Post not found")
        
        post.published = True
        post.published_at = datetime.now()
        return await self.post_repo.save(post)

---

Building REST APIs

Request Mapping Decorators

from starspring import (
    Controller, 
    GetMapping, 
    PostMapping, 
    PutMapping, 
    DeleteMapping,
    PatchMapping
)

@Controller("/api/posts")
class PostController:
    @GetMapping("")
    async def list_posts(self):
        # GET /api/posts
        pass
    
    @GetMapping("/{id}")
    async def get_post(self, id: int):
        # GET /api/posts/123
        pass
    
    @PostMapping("")
    async def create_post(self, title: str, content: str):
        # POST /api/posts
        pass
    
    @PutMapping("/{id}")
    async def update_post(self, id: int, title: str, content: str):
        # PUT /api/posts/123
        pass
    
    @DeleteMapping("/{id}")
    async def delete_post(self, id: int):
        # DELETE /api/posts/123
        pass

Parameter Injection

StarSpring automatically injects parameters from:

• Path variables: /{id} → id: int
• Query parameters: ?page=1 → page: int
• Request body: JSON payload → function parameters

@GetMapping("/search")
async def search_posts(
    self, 
    query: str,           # From ?query=...
    page: int = 1,        # From ?page=... (default: 1)
    limit: int = 10       # From ?limit=... (default: 10)
):
    # Implementation
    pass

Response Handling

Return entity directly:

@GetMapping("/{id}")
async def get_post(self, id: int):
    post = await self.post_service.get_post(id)
    return post  # Auto-serialized to JSON

Use ResponseEntity for control:

from starspring import ResponseEntity

@GetMapping("/{id}")
async def get_post(self, id: int):
    post = await self.post_service.get_post(id)
    if post:
        return ResponseEntity.ok(post)
    return ResponseEntity.not_found()

ResponseEntity methods:

• ResponseEntity.ok(body) - 200 OK
• ResponseEntity.created(body) - 201 Created
• ResponseEntity.accepted(body) - 202 Accepted
• ResponseEntity.no_content() - 204 No Content
• ResponseEntity.bad_request(body) - 400 Bad Request
• ResponseEntity.unauthorized(body) - 401 Unauthorized
• ResponseEntity.forbidden(body) - 403 Forbidden
• ResponseEntity.not_found(body) - 404 Not Found
• ResponseEntity.status(code, body) - Custom status

Request Body Validation

from pydantic import BaseModel

class CreatePostRequest(BaseModel):
    title: str
    content: str
    published: bool = False

@PostMapping("")
async def create_post(self, request: CreatePostRequest):
    # Pydantic validates automatically
    post = await self.post_service.create_post(
        title=request.title,
        content=request.content,
        published=request.published
    )
    return ResponseEntity.created(post)

---

Working with Templates

StarSpring integrates Jinja2 for server-side rendering.

Setup Templates Directory

my_app/
├── templates/
│   ├── index.html
│   ├── post.html
│   └── layout.html
├── static/
│   ├── css/
│   └── js/
└── main.py

Configure Template Path

from starspring import StarSpringApplication

app = StarSpringApplication(title="My Blog")
app.add_template_directory("templates")
app.add_static_files("/static", "static")

Template Controller

from starspring import TemplateController, GetMapping, ModelAndView

@TemplateController("")
class WebController:
    def __init__(self, post_service: PostService):
        self.post_service = post_service
    
    @GetMapping("/")
    async def index(self) -> ModelAndView:
        posts = await self.post_service.get_recent_posts()
        return ModelAndView("index.html", {
            "posts": posts,
            "title": "My Blog"
        })
    
    @GetMapping("/post/{id}")
    async def view_post(self, id: int) -> ModelAndView:
        post = await self.post_service.get_post(id)
        return ModelAndView("post.html", {"post": post})

Template Files

templates/layout.html:

<!DOCTYPE html>
<html>
<head>
    <title>{% block title %}My Blog{% endblock %}</title>
    <link rel="stylesheet" href="/static/css/style.css">
</head>
<body>
    <nav>
        <a href="/">Home</a>
    </nav>
    <main>
        {% block content %}{% endblock %}
    </main>
</body>
</html>

templates/index.html:

{% extends "layout.html" %}

{% block title %}{{ title }}{% endblock %}

{% block content %}
<h1>Recent Posts</h1>
{% for post in posts %}
    <article>
        <h2><a href="/post/{{ post.id }}">{{ post.title }}</a></h2>
        <p>{{ post.content[:200] }}...</p>
        <small>{{ post.created_at }}</small>
    </article>
{% endfor %}
{% endblock %}

---

Middleware

Built-in Middleware

StarSpring includes:

• ExceptionHandlerMiddleware: Catches and formats exceptions
• LoggingMiddleware: Logs requests and responses
• CORSMiddleware: Handles Cross-Origin Resource Sharing

Enable CORS

from starspring import StarSpringApplication
from starspring.middleware.cors import CORSConfig

app = StarSpringApplication(title="My API")

cors_config = CORSConfig(
    allow_origins=["http://localhost:3000"],
    allow_methods=["GET", "POST", "PUT", "DELETE"],
    allow_headers=["*"],
    allow_credentials=True
)

app.add_cors(cors_config)

Custom Middleware

from starlette.middleware.base import BaseHTTPMiddleware
from starlette.requests import Request

class CustomMiddleware(BaseHTTPMiddleware):
    async def dispatch(self, request: Request, call_next):
        # Before request
        print(f"Request: {request.method} {request.url}")
        
        # Process request
        response = await call_next(request)
        
        # After request
        print(f"Response: {response.status_code}")
        
        return response

# Add to application
from starlette.middleware import Middleware

app = StarSpringApplication(title="My API")
app._middleware.append(Middleware(CustomMiddleware))

---

Advanced Features

Lifecycle Hooks

app = StarSpringApplication(title="My API")

@app.on_startup
async def startup():
    print("Application starting...")
    # Initialize resources

@app.on_shutdown
async def shutdown():
    print("Application shutting down...")
    # Cleanup resources

Environment-Specific Configuration

# application.yaml
spring:
  profiles:
    active: ${ENVIRONMENT:development}

---
# Development profile
spring:
  profiles: development
database:
  url: "sqlite:///dev.db"

---
# Production profile
spring:
  profiles: production
database:
  url: "postgresql://user:pass@prod-db/myapp"

Manual Component Registration

from starspring.core.context import get_application_context

# Register bean manually
context = get_application_context()
context.register_bean("my_service", MyService())

# Get bean
service = context.get_bean(MyService)

Custom Repository Methods

from starspring.data.query_builder import QueryOperation

@Repository
class PostRepository(StarRepository[Post]):
    async def find_published_posts(self) -> list[Post]:
        # Custom SQL query
        return await self._gateway.execute_query(
            "SELECT * FROM posts WHERE published = :published",
            {"published": True},
            Post,
            QueryOperation.FIND
        )

---

Examples

Complete examples are available in the examples/ directory:

• examples/test1: Basic CRUD API with users
• examples/blog: Blog application with templates
• examples/microservice: Microservice architecture example

---

Contributing

Contributions are welcome! Please:

1. Fork the repository
2. Create a feature branch (git checkout -b feature/amazing-feature)
3. Commit your changes (git commit -m 'Add amazing feature')
4. Push to the branch (git push origin feature/amazing-feature)
5. Open a Pull Request

---

License

StarSpring is released under the MIT License. See LICENSE file for details.

---

Support

• Documentation: https://github.com/DasunNethsara-04/starspring
• Issues: https://github.com/DasunNethsara-04/starspring/issues
• Discussions: https://github.com/DasunNethsara-04/starspring/discussions

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Built with love for the Python community by developers who appreciate Spring Boot's elegance.