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For any type of distributed application a dialogue that forms a set of exchanges between a client program and a server program is very important. This is no less true of Web-based applications that use HTML and a client browser communicating with a Java-based Web application. Indeed, in some ways it is much more important, as the underlying HTTP communications protocol used in such applications is connectionless. That is, it does not establish a connection that is used for the duration of the dialogue! Instead, each time a message is sent to the Web container from the Web browser a completely new connection is made. This means that the presence of an established connection cannot be used to represent a continuation of a dialogue (or session). Instead some other way of identifying the session is required. In this chapter we explore how Web applications support the concept of a user session. |
