What is the purpose of middleware in Django?

The purpose of Django middleware is to perform common functions or operations during the process of handling requests and responses. They can modify, validate, log, or perform other actions on requests and responses before or after the view function processes the request. Middleware can be applied to every request in a Django project, providing a unified way to handle common functionalities.

Common middleware functions include:

1. Authentication and authorization: Middleware can be used to verify a user’s identity and permissions, such as checking if a user is logged in or has access to a specific page.
2. Log recording: Middleware can be used to record logs of requests and responses, including information such as the URL of the request, request parameters, response status code, etc., making it convenient for subsequent debugging and analysis.
3. Request/Response Handling: Middleware can modify requests and responses, such as adding necessary request headers, parsing request data, processing response data, etc.
4. Cache: Middleware can be used to implement caching functionality for responses, reducing the need to access databases or other external resources.
5. Error handling: Middleware can catch and manage exceptions that occur during the request handling process, such as returning custom error pages or messages.

Django comes with some default middleware and also supports custom middleware to meet specific project needs. The order of middleware can be adjusted through configuration files to ensure they execute in the desired sequence.