What is @aws-sdk/middleware-stack?
@aws-sdk/middleware-stack is a package that provides a mechanism to compose middleware in the AWS SDK for JavaScript. It allows developers to add, remove, and modify middleware in the request/response lifecycle, enabling custom logic to be executed at various stages of the request processing.
What are @aws-sdk/middleware-stack's main functionalities?
Adding Middleware
This feature allows you to add custom middleware to the middleware stack. The middleware can perform actions before and after the request is processed.
const { MiddlewareStack } = require('@aws-sdk/middleware-stack');
const stack = new MiddlewareStack();
const myMiddleware = (next, context) => async (args) => {
console.log('Before request');
const result = await next(args);
console.log('After request');
return result;
};
stack.add(myMiddleware, {
step: 'initialize',
name: 'myMiddleware',
priority: 'high'
});
// Use the stack in a client
const client = new SomeAWSClient({ middlewareStack: stack });
Removing Middleware
This feature allows you to remove middleware from the middleware stack by specifying its name.
const { MiddlewareStack } = require('@aws-sdk/middleware-stack');
const stack = new MiddlewareStack();
const myMiddleware = (next, context) => async (args) => {
console.log('Before request');
const result = await next(args);
console.log('After request');
return result;
};
stack.add(myMiddleware, {
step: 'initialize',
name: 'myMiddleware',
priority: 'high'
});
// Remove the middleware
stack.remove('myMiddleware');
Modifying Middleware
This feature allows you to modify existing middleware in the middleware stack by adding a new middleware with the same name and step.
const { MiddlewareStack } = require('@aws-sdk/middleware-stack');
const stack = new MiddlewareStack();
const myMiddleware = (next, context) => async (args) => {
console.log('Before request');
const result = await next(args);
console.log('After request');
return result;
};
stack.add(myMiddleware, {
step: 'initialize',
name: 'myMiddleware',
priority: 'high'
});
// Modify the middleware
stack.add((next, context) => async (args) => {
console.log('Modified middleware');
return next(args);
}, {
step: 'initialize',
name: 'myMiddleware',
priority: 'high'
});
Other packages similar to @aws-sdk/middleware-stack
express
Express is a minimal and flexible Node.js web application framework that provides a robust set of features for web and mobile applications. It allows for the use of middleware to handle requests and responses, similar to how @aws-sdk/middleware-stack allows for middleware in the AWS SDK.
koa
Koa is a new web framework designed by the team behind Express, aiming to be a smaller, more expressive, and more robust foundation for web applications and APIs. Koa uses async functions and provides a suite of methods for writing middleware, similar to @aws-sdk/middleware-stack.
hapi
Hapi is a rich framework for building applications and services. It enables developers to focus on writing reusable application logic instead of spending time building infrastructure. Hapi's plugin system is similar to the middleware stack in @aws-sdk/middleware-stack.