Servlet event listener

• Implement the javax filter. servlet. filter interface, which intercepts a servlet program and becomes a level on the communication line between the servlet container and the servlet program, it can intercept the requests sent from the servlet container to the servlet program and the Response sent from the servlet program back to the servlet container, and decide whether to pass the requests to the servlet program, and whether the request and response information is modified.
• Servlet event listeners are used to listen to the creation and destruction of domain objects, such as servletcontext, httpsession, and servletrequest in Web applications, and to listen to events in which attributes of objects are modified.

Servlet event listener