What types of objects does middleware usually process?

Middleware typically processes the following types of objects:

• Requests and responses: for example, HTTP requests and responses in web applications.
• Messages: in message queue systems, these can be messages between services.
• Sessions and contexts: data about user or transaction state, passed between components.
• Authentication and authorization data: tokens, cookies, security headers.

Middleware acts as an intermediary layer that intercepts and processes these objects to add functionality (logging, authentication, routing, etc.) without modifying the main application.