Web Programming: APIs and Web Services (REST, GraphQL)

APIs and web services, such as REST and GraphQL, are fundamental to the development of modern web applications, as they enable communication between different systems and platforms. REST (Representational State Transfer) is an architectural style based on the use of HTTP, which facilitates the creation of scalable and simple web services using standard methods such as GET, POST, PUT, and DELETE. GraphQL, on the other hand, is a query language that allows clients to obtain exactly the data they need, improving efficiency and flexibility by avoiding excessive or insufficient requests for information. Both approaches are key to effectively and dynamically integrating and connecting web applications.

What is an API and a Web Service?

An API (Application Programming Interface) allows different systems to interact with each other. A web service is an implementation of an API that allows data exchange over the internet.

Main API Technologies

REST: Resource-based architecture and the use of HTTP. Use methods like GET, POST, PUT, and DELETE.
GraphQL: A query language developed by Facebook that allows clients to request only the data they need.

Example of a REST API in Node.js with Express

This code shows how to create a basic REST API with Node.js and Express:

const express = require('express');
const app = express();

app.get('/greeting', (req, res) => {
    res.json({ message: 'Hello, World from REST API!' });
});

app.listen(3000, () => {
    console.log('REST API running at http://localhost:3000');
});

REST APIs use routes to define resources and return responses in JSON format.

Example of a GraphQL API in Node.js with Express

This code shows how to define a GraphQL API in Node.js:

const { graphqlHTTP } = require('express-graphql');
const { buildSchema } = require('graphql');
const express = require('express');

// Define the GraphQL schema
const schema = buildSchema(`
  type Query {
    greeting: String
  }
`);

// Root resolver for the greeting query
const root = {
  greeting: () => 'Hello, World from GraphQL!'
};

const app = express();

// Set up the /graphql endpoint to handle GraphQL requests
app.use('/graphql', graphqlHTTP({
  schema: schema,
  rootValue: root,
  graphiql: true  // Enables the GraphiQL interface in the browser
}));

// Start the server on port 4000
app.listen(4000, () => {
  console.log('GraphQL API running at http://localhost:4000/graphql');
});

GraphQL allows for flexible queries, returning only the data requested by the client.

Conclusion

REST and GraphQL are powerful tools for building APIs and web services. The choice depends on the project's needs: REST is more traditional and widely adopted, while GraphQL offers greater query flexibility.