| <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> |
| <html> |
| <head> |
| <META http-equiv="Content-Type" content="text/html; charset=UTF-8"> |
| <title>Advanced Control Flow</title> |
| <link href="http://purl.org/DC/elements/1.0/" rel="schema.DC"> |
| <meta content="Ovidiu Predescu" name="DC.Creator"> |
| </head> |
| <body> |
| |
| <h1>Cocoon and continuations</h1> |
| |
| <p>With continuations in the language, you can essentially |
| store the continuation of <span class="codefrag">sendPageAndWait()</span> (think of all |
| the stack trace, and the program counter), put it in a global |
| hash table associated with an id. The id is then encoded in |
| the <span class="codefrag">response.xml</span> page as an URL. When the user |
| clicks on that URL, on the server side the associated |
| continuation is resumed. Resuming the processing happens as if |
| nothing was stopped, you get all the stack trace back, and all |
| the local variables.</p> |
| |
| |
| <p>So instead of using beans to store things in session, you |
| use normal variables in a program. Since each user has its own |
| version of the program, all the local variables in the program |
| are separate between users.</p> |
| |
| |
| <p>With this approach clicking the <em>Back</em> button in the |
| browser is no longer a hassle to deal with for you as a |
| server-side programmer. They will simply refer to past |
| continuations objects, which have their own state of the local |
| variables.</p> |
| |
| |
| <p>Since continuations are objects, you can also store them in |
| a database, for really long-lived session, just like you do |
| with session beans.</p> |
| |
| |
| |
| </body> |
| </html> |
