INTERACTIVE WEB SERVICES WITH JAVA

Sessions in JWIG

In CGI-scripts, Servlets, and JSP the session concept is implicit:

individual interactions are tied together by the action attributes in the forms
the client identity of a session must be stored in cookies, hidden fields, or the URL
local state must be explicitly saved and restored across all interactions with the client

In JWIG, the session concept is explicit:

a Session is written as a sequential program (just like an ordinary Java method)
interactions with the client are similar to remote method invocations
the local state is automatically the full state of the thread running the Session:
- all local variables, regardless of their type or complexity
- the full stack of method invocations

The "Hello World" example:

import dk.brics.jwig.runtime.*;

public class Hello extends Service 
{
    public class Example extends Session 
    {
        public void main() {
            XML x = [[ <html><head><title>JWIG</title></head><body>
                       <h1><[what]></h1>
                       <form><input type="submit" /></form>
                       </body></html> ]];
            x = x <[ what = [[ Hello World! ]] ];
            show x;
            XML y = [[ <html><head><title>JWIG</title></head><body>
                       Goodbye!</body></html> ]];
            exit y;
        }
    }
}