mhm, have you ever looked at the spring webflow project?
It seems like they have already done a lot in this direction. The only
thing missing is the integration with tapestry :-(
markus
On 11/15/05, John Coleman <[EMAIL PROTECTED]> wrote:
> > Now we don't have a centralized location to specify such configuration (or
> > I'm not aware about it, like struts-config.xml), is this a reason people
> > plug it with Spring. Meanwhile I'll try to study some of trails.
>
> On the larger projects I have worked on, the team often come into conflict
> with using struts-config - most people seem to want it most of the time,
> especially at the start of the project. With Tapestry developers can at
> least deal with well decoupled units of work.
>
> Having said that I did start work on an idea to drive the navigation using
> Drools. This would operate like struts-config, but would also have potential
> to create far more complex navigation experiences, ideal for the more
> sophisticated web shops, who need to tailor for a clients individual needs.
> Of course, it does mean you have some untestable loosly bounds script doing
> a significant job! This is satisfying from an architectural perspective,
> because it farms out business logic, and lets the page be really simple. Nav
> rules are really part of the business logic, yet another reason why Struts
> is pants IMHO. Ideally pages should not contain any logic for what comes
> next.
>
> I started by extending BasePage, then you can implement a next page method
> and let Drools handle the actual value used. Here is an example of the
> good'ol max login attempt handling. Rather too simple to justify the method,
> but just an example. I'm conscious now that this should be handled by a
> hivemind service, but this code was written for Tapestry 3 standalone, and
> is rather yukky. A much nicer approach would be for a simple service that
> returns the name of the next page. The unpleasantry is in marshalling the
> required data for the working memory - so that the method is not fully
> decoupled. It would be nice for something to do that as required by the
> rules.
>
> You could also write your own digester to implement a struts-config like
> navigation service. You could even copy the relivant parts of the
> struts-config dtd. And you could make the digester accomodate multiple
> files, each containing its own nav rules, and merge them, thus avoiding file
> sharing conflicts. The Drools approach gives you far more flexibility
> though.
>
> John
>
> public class DRLBasePage extends BasePage {
>
> static URL url;
>
> static RuleBase ruleBase;
>
> WorkingMemory workingMemory;
>
> static {
>
> try {
>
> url = DRLBasePage.class.getResource("cycle.drl");
>
> ruleBase = RuleBaseBuilder.buildFromUrl(url);
>
> } catch (Exception e) {e.printStackTrace();}
>
> }
>
>
> public DRLBasePage() {
>
> workingMemory = ruleBase.newWorkingMemory();
>
> }
>
> // method to obtain the next page for the given working memory and cycle
>
> public void nextPage(IRequestCycle cycle) throws FactException {
>
> workingMemory.assertObject(this); // pass in this page object
>
> workingMemory.setApplicationData("cycle", cycle); // pass in the cycle to
> allow Drools to perform the forward
>
> // you may want to load additional data into working memory here which sadly
> starts to create loose coupling!
>
> // a suggestion is to ensure those data are page properties instead, so they
> can be picked up with the assert object method
>
> workingMemory.fireAllRules(); // this will implement the next page nav
>
> }
>
> }
>
>
>
> /*
>
> * If the user enters valid credentials they are stored in the visit
>
> * and an attempt is made to go to the next page.
>
> *
>
> */
>
> package examples;
>
> import org.apache.tapestry.IRequestCycle;
>
> import html.DRLBasePage;
>
> /**
>
> * Login page.
>
> */
>
> public abstract class Login extends DRLBasePage
>
> {
>
> public abstract String getUserName();
>
> public abstract String getPassword();
>
> public abstract void setMessage(String message);
>
> public void login(IRequestCycle cycle)
>
> {
>
> if (isValidLogin(getUserName(), getPassword()))
>
> {
>
> // Get the Visit and cast it to our application-specific
>
> // class.
>
> ((Visit) getVisit()).doLogin(getUserName(), getPassword());
>
> // use Drools to obtain next page
>
> try {
>
> nextPage(cycle);
>
> } catch (Exception e) {e.printStackTrace();}
>
> return;
>
> }
>
> // this sets the message property for the page to display
>
> setMessage("invalid user name or password - attempt "
>
> + ((Visit) getVisit()).getLoginAttempts());
>
> }
>
> private boolean isValidLogin(String userName, String password)
>
> {
>
> ((examples.Visit) getVisit()).incLoginAttempts();
>
> return "tapestry".equalsIgnoreCase(userName);
>
> }
>
> }
>
>
>
>
>
>
>
> // a problem with this method is the need of the page to load any data that
> the rules need, so that there is some yukky loose coupling
>
> // any ideas on how to get that code out much appreciated, but initially it
> is best to use page properties
>
> <?xml version="1.0"?>
>
> <rule-set name="Cycle" xmlns="http://drools.org/rules";
> xmlns:java="http://drools.org/semantics/java";>
>
> <rule name="login_success">
>
> <parameter identifier="page">
>
> <java:class>html.DRLBasePage</java:class>
>
> </parameter>
>
> <java:condition>page instanceof examples.Login</java:condition>
>
> <java:condition>((examples.Visit) page.getVisit()).getLoginAttempts() <
> 4</java:condition>
>
> <java:consequence>
>
> ((examples.Visit) page.getVisit()).logAccess();
>
> cycle.activate("Main");
>
> </java:consequence>
>
> </rule>
>
> <rule name="login_failure">
>
> <parameter identifier="page">
>
> <java:class>html.DRLBasePage</java:class>
>
> </parameter>
>
> <java:condition>page instanceof examples.Login</java:condition>
>
> <java:consequence>
>
> ((examples.Login) page).setMessage("Too many login attempts!");
>
> </java:consequence>
>
> </rule>
>
> </rule-set>
>
>
>
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