Institute of Information Science - University of Miskolc

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==== GraphQL Integration ====

Official documentation:

https://graphql.org/learn/

Comparison of main characteristics with REST API.

|         | **REST API** | **GraphQL** |
| **Query flexibility** | Fixed endpoints and responses | Flexible queries, only the required data is returned |
| **Client performance** | Multiple requests needed for different resources | Data from multiple sources can be queried in a single request |
| **Data** | Multiple queries may be needed for complex data | All required data can be fetched in a single request |
| **Network efficiency** | Network traffic increases with multiple requests | Reduces unnecessary data transfer and number of queries |
| **Usability** | Simple, widely known | More difficult to learn, but more efficient |
| **Caching** | HTTP cache and CDN supported | Harder to implement, requires custom caching strategy |
| **Versioning** | API versioning needed (e.g. `/v1/users`) | No versioning needed, the client selects the required fields |
| **Handling schema changes** | Changes may require new endpoints | New fields can be added while keeping the old ones |
| **Security and access control** | Built-in HTTP security, roles | Fine-grained access rules needed (e.g., field-level permissions) |
| **Supported formats** | Usually JSON (but others supported) | JSON-based (strictly follows GraphQL schema) |
| **Use cases** | Ideal for simple CRUD APIs | Better choice for complex, dynamic client needs |

After creating a Python virtual environment, you can install the required dependencies with the following command:

<code>
pip install fastapi strawberry-graphql uvicorn
</code>

Sample code for first use:

<sxh python>
import strawberry
from fastapi import FastAPI
from strawberry.fastapi import GraphQLRouter

# User data model
@strawberry.type
class User:
    id: int
    name: str
    age: int

# Example database
users = [
    User(id=1, name="Noa", age=30),
    User(id=2, name="Anna", age=25),
]

# GraphQL Query class
@strawberry.type
class Query:
    @strawberry.field
    def get_users(self) -> list[User]:
        return users

# GraphQL Mutation class (add new user)
@strawberry.type
class Mutation:
    @strawberry.mutation
    def create_user(self, name: str, age: int) -> User:
        new_user = User(id=len(users) + 1, name=name, age=age)
        users.append(new_user)
        return new_user

# Create GraphQL schema
schema = strawberry.Schema(query=Query, mutation=Mutation)

# Create FastAPI app
app = FastAPI()

# Register GraphQL endpoint
graphql_app = GraphQLRouter(schema)
app.include_router(graphql_app, prefix="/graphql")
</sxh>

<code>
uvicorn.exe main:app --reload
</code>

The GraphQL Playground will be available at the following URL:
👉 http://127.0.0.1:8000/graphql

----

===== Sample Task: Library System with GraphQL =====

==== Task Description ====
Create a simple GraphQL API to manage data in a library system. The system should store books and authors, and allow adding new books.

==== Requirements ====

The GraphQL schema should include the following types:

  * **Author**:
    * `id` (Int)
    * `name` (String)

  * **Book**:
    * `id` (Int)
    * `title` (String)
    * `author` (Author)
    * `year` (Int)

==== Features to Implement ====

  * **Queries:**
    * List all books (title, author name, year)
    * List books by a specific author (searched by name)

  * **Mutations:**
    * Add a new book with the following fields: title, author ID, year

==== Example Query ====

<code javascript>
query {
  books {
    title
    author {
      name
    }
    year
  }
}
</code>

==== Example Mutation ====

<code javascript>
mutation {
  addBook(title: "1984", authorId: 1, year: 1949) {
    id
    title
    author {
      name
    }
  }
}
</code>

==== Technical Requirements ====

  * Use **FastAPI** and **Strawberry GraphQL** libraries
  * Store data using built-in lists (e.g., `authors`, `books`)
  * The GraphQL endpoint should be accessible at `http://127.0.0.1:8000/graphql`

==== Bonus ====

  * Implement a new mutation to add an author by name
  * Implement a query to list books by a given year