Re: [JBoss-user] Jetty and Clustering ..

Jules Gosnell Thu, 14 Nov 2002 13:22:11 -0800

I've just notice that you are using 3.2beta ?

Try in 3.0.4 - if it doesn't work there, we have a problem. If it does, you should wait for the next 3.2 release - out very soon, I believe

Jules

Barlow, Dustin wrote:

I tried what you suggested, but it still doesn't function right.

Below is test.jsp which sets up the initial session object:
<%@ page import="java.util.*"%>
<html>
<head>
<title>Test Page</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
</head>
<body leftmargin="4" topmargin="4">
<jsp:useBean id="sessionInfo" scope="session"
class="org.foo.session.SessionInfo"/>
<%
 sessionInfo.setInfo("Info was set on the test.jsp page");

 session.setAttribute("sessionInfo", session.getAttribute("sessionInfo"));

 // This was added just to see if "sessionInfo" was stored in the session
object, and it was
 Enumeration enum = session.getAttributeNames();
 while(enum.hasMoreElements()) {
 out.println(enum.nextElement().toString());
 }
 out.println("" + sessionInfo.getInfo() + "");
%>
</body>
</html>

Below is test2.jsp which should display the information stored in the
SessionInfo bean:

<html>
<head>
<title>Test Page</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
</head>
<body leftmargin="4" topmargin="4">
<jsp:useBean id="sessionInfo" scope="session"
class="org.foo.ntarget.session.SessionInfo"/>
We are on test page 2
<%out.println(sessionInfo.getInfo());%>
</body>
</html>


If I remove <distributable/> from web.xml, then test2.jsp will show "Info
was set on the test.jsp page" as expected. So something else still isn't
right.

Dustin
-----Original Message-----
From: Jules Gosnell [mailto:jules@;mortbay.com]
Sent: Thursday, November 14, 2002 11:25 AM
To: [EMAIL PROTECTED]
Subject: Re: [JBoss-user] Jetty <jsp:useBean> and Clustering ..

Here is a reply I wrote to the same problem recently - the guy came back and told me it worked fine:

Bernie,

I haven't had time to run the app, but I think that I know what is happening.

Imagine you are talking to a remote object (e.g. an EJB).
you create a HashTable - ht
you call bean.setHashTable(ht);
you call ht.put("test", "123");
you call bean.getHashTable();

would you expect the returned HashTable to contain "test" - NO, because when talking to a remote/distributed object your semantics shift from REFERENCE to VALUE. Thus with a local session you can put in an object and maintain a reference to that object, however with my (current) distributable impl, you can only COPY an object into it.

To update an object that is already in the session, you just put it in again. This tells Jetty to redistribute this attribute. Without this kick we have no idea when you may have changed an object and have no option other than to periodically redistribute the entire session - expensive.

As soon as I find the time, I shall adapt my current impl to be a hybrid of the two strategies outlined above.

Now to specifics.

All you need to do is ensure that if you mess with anything kept in the session in your JSPs, you then call setAttibute() again with them. This will copy the new value into the session and force immediate distribution.

I'm no JSP expert, but I believe that you can declare beans as being within session scope, then act upon them by name ?, In this case you will need to figure out where in the session Jasper is keeping the bean and call session.setAttribute(<bean-name?>, session.getAttribute(<bean-name>)); afterwards, or something similar.

Done this way your code will still work in non-distributable mode, since we have not extended the spec.

Hope this makes sense.

Try it out and come back to me with any problems - I am off air until monday.

Jules

Barlow, Dustin wrote:

Has anyone gotten <jsp:useBean> style session's to propagate
across clusters
in 3.x (3.2.0beta2 in my case)?

For example:

<jsp:useBean id="userInfo" scope="session"
class="org.foo.session.UserInfo"/>

I have found that if I include the <distributable/> tag in
my web.xml file,
that any session scoped classes no longer work between pages
on the _same_
server instance. If I set a String member variable in the
UserInfo object
on one jsp page and then try to reference it from a second
jsp page, it is
always null. If I remove <distributable/> from web.xml,
then the object's
member values do survive across multiple jsp calls. The
UserInfo object is
also not being propagated to any of the cluster nodes
either. (I am running
the "All" target with all default settings).

Dustin Barlow

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Re: [JBoss-user] Jetty and Clustering ..

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