What are the objects of the four domains of JavaWeb

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one。 Introduction

There are four domain objects in JavaWeb. According to their scope of action, they are PageContext, Request, Session and application. The following is mainly for the scope of action, life cycle are introduced.

two。 PageContext

a. Scope of action

Next to PageContext, there is only one request, which is mainly used for request forwarding.

b. Life cycle

It is created by the server before the service method call; at the end of the request, the end of the life cycle is destroyed.

four。 Session

a. Scope of action

The scope of action is the largest, and the scope is limited to the current web application; as long as the property is set in one place, the jsp or servlet in other places can be obtained, and the corresponding ServletContext object in servlet

b.