Thanks for all the reply and discussion on the question I asked. I am very interested in doing some proof-of-concept work by sharing the ClassLoader on two web apps.
Can someone show me some sample code on how to specify a common class loader for two different web apps? I am running WebLogic 6.1. Thanks... -----Original Message----- From: Joseph Barefoot [mailto:[EMAIL PROTECTED]] Sent: Thursday, June 13, 2002 2:50 PM To: Struts Users Mailing List Subject: RE: Please help clarify or confirm -- HttpSession > The container makes sure that Session ID's are unique. It sets the cookie > as well - nothing in the webapp has to do this. This is just how the > containers work. Of course. > > Regarding storing "objects from webapp A in a shared classloader class > keyed by the sessionID and retrieve them from > webapp B". > > First, you can't physically store an object in another webapp because the > memory spaces are isolated from each other. Second, having common > directories on the two CLASSPATHS for the two webapps allows you to load > CLASSES to create new objects, but not to share the objects once they are > created. True, but not what I suggested at all. Two webapps sharing a common CLASSPATH is far different from them having access to a common (shared,parent) CLASSLOADER. In the former two different classloaders are loading the same class into two different "memory spaces", as you say. In the latter, a parent classloader is loading a class into a "memory space" accessible by either of the two child classloaders for the webapps. So I fail to see why a static class with static resources loaded by this parent classloader will not enable objects to be shared between the two child classloaders, so long as the objects themselves are also created from classes loaded by the shared classloader. Note that I am also not claiming that this will 100% work, I just don't see why it wouldn't. > > But there are ways to share objects (in addition to classes) between > webapps. And at times there may be good reasons to do so. > > For example, imagine you have an object representing a transaction to be > executed on your system (maybe a stock trade). What if: > > - The user who entered the transaction wants to see its real-time status. > - A trader who is going to execute the transaction needs to see it, and > - An auditor needs to monitor all trades currently in the system. > > Imagine also you want them to use three seperate webapps (or non-servlet > applications) to do their work. While not the only approach, it > is possible > to have all access the same physical Java object. Here are some ways: > > 1. Implement the Object as an Entity EJB in an EJB container such > as JBOSS. > Have all the webapps (or whatever) connect to the same EJB Container > instance and manipulate the data in the object. The EJB container will > manage locking and transactional integrity for you as well. > > 2. Create the object as a singleton in some JVM somewhere and wrap an RMI > server around it. This is basically a hack, but I saw it done > once to allow > clustered applications to share Properties objects between them (ensuring > they were all using the same Properties). (And, yes - it was a pain.) > > 3. Put the object behind a web service and access it via SOAP. This allows > some of the clients to be non-Java. > > All these solutions are based on putting the object in some place OUTSIDE > any of the individual webapps. Putting an object into a shared classloader DOES put it OUTSIDE of any of the individual webapps, in that that object's existence is not dependent on the existence of any webapp. If this were not true, then the classloader hierarchy employed by app. servers would be meaningless. peace, joe > > > > > > > > > > > > > > > > > > > > "Joseph Barefoot" <[EMAIL PROTECTED]> on 06/13/2002 02:09:43 PM > > Please respond to "Struts Users Mailing List" > <[EMAIL PROTECTED]> > > To: "Struts Users Mailing List" <[EMAIL PROTECTED]> > cc: (bcc: Kevin Bedell/Systems/USHO/SunLife) > Subject: RE: Please help clarify or confirm -- HttpSession > > > hmmm...but the sessionIDs have to be unique, even across web apps., > correct? > If there weren't unique, URL rewriting would not work correctly if two > users > using two webapps on the same app. server happened to get the same session > ID. Therefore, one *should* be able to store objects from webapp A in a > shared classloader class keyed by the sessionID and retrieve them from > webapp B. > > Am I missing something here? (besides why the hell you would want to do > this) > :) > > > joe > > > -----Original Message----- > > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] > > Sent: Thursday, June 13, 2002 10:46 AM > > To: Struts Users Mailing List > > Subject: RE: Please help clarify or confirm -- HttpSession > > > > > > > > In general, there is no way session info from one webapp can be made > > visible to other webapps. Some details of this may vary > depending on your > > app server. > > > > Sessions are controlled by cookies being set on the client. The > "cookies" > > that are set by each webapp are scoped for that webapp only. As > > an example, > > create the following .jsp file and name it session.jsp. Put it in > > "webapp1" > > > > <html> > > <head> > > <title>Testing Session Management</title> > > </head> > > <body> > > <% out.print("Session ID = " + request.getSession().getId() ); %> > > </body> > > </html> > > > > > > > > Then, if you were to do a low-level http request from the server, > > you'd see > > something like: > > > > > > bash-2.05$ ./telnet -E localhost 8080 [ <-- I type ] > > Trying 127.0.0.1... > > Connected to localhost. > > Escape character is 'off'. > > > > GET /webapp1/session.jsp HTTP/1.0 [ <-- I type ] > > > > HTTP/1.1 200 OK > > Content-Type: text/html;charset=ISO-8859-1 > > Date: Wed, 12 Jun 2002 00:39:49 GMT > > Server: Apache Tomcat/4.0.3 (HTTP/1.1 Connector) > > Connection: close > > Set-Cookie: JSESSIONID=AC75B22FD1D283D1CEF0136928110679;Path=/webapp1 > > > > <html> > > <head> > > <title>Testing Session Management</title> > > </head> > > <body> > > Session ID = AC75B22FD1D283D1CEF0136928110679 > > </body> > > </html> > > > > Connection closed by foreign host. > > bash-2.05$ > > > > > > The JSESSIONID cookie is used by the servlet container to > manage the user > > session. > > > > > > Notice that the the scope of the JSESSIONID Cookie in this example is > > limited to the '/webapp1' web application. So even if you have many web > > applications (or Struts applications) deployed in a servlet container, > > session tracking is isolated between them. > > > > > > > > <ShamelessPlug> > > I'll be covering topics such as this and others in my upcoming book > > "Struts: Rapid Working Knowledge" to be published by SAMS later this > year. > > </ShamelessPlug> > > > > > > HTH, > > > > Kevin > > > > > > > > > > > > "Jerry Jalenak" <[EMAIL PROTECTED]> on 06/13/2002 01:43:50 PM > > > > Please respond to "Struts Users Mailing List" > > <[EMAIL PROTECTED]> > > > > To: "'Struts Users Mailing List'" <[EMAIL PROTECTED]> > > cc: (bcc: Kevin Bedell/Systems/USHO/SunLife) > > Subject: RE: Please help clarify or confirm -- HttpSession > > > > > > This is something I've wondered about, especially in a team development > > environment where there are several programmers working on different > > webapps > > that need to share a common framework - in other words, something like > > this: > > > > Tomcat\webapps > > framework-application > > WEB-INF > > ... > > webapplication_1 > > WEB-INF > > ... > > webapplication_2 > > WEB-INF > > ... > > etc etc etc > > > > Can the classes in webapplication_1 'see' session data that was > > created and > > stored in the session by the framework-application? > > > > Jerry > > > > -----Original Message----- > > From: emmanuel.boudrant [mailto:[EMAIL PROTECTED]] > > Sent: Thursday, June 13, 2002 12:39 PM > > To: Struts Users Mailing List > > Subject: Re: Please help clarify or confirm -- HttpSession > > > > > > > > At my knowledge, under tomcat each webapp have his own > > "memory space" so you can't share HttpSession between > > 2 webapp. You can share object between 2 webapp with > > one condition, the class to be shared must be loaded > > in same ClassLoader. > > > > > > Did you understand my english ;) > > > > -Emmanuel > > > > > > > > --- "Yuan, Tony" <[EMAIL PROTECTED]> a écrit : > > > Hi Guys, > > > Can anyone help clarify or confirm the relationship > > > between an HttpSession > > > and a web application? I mean, can two WAR (two > > > application) share one > > > common HttpSession and whatever resource this > > > HttpSession contains? > > > > > > My understanding is that if WARs are deployed > > > separately, then there will be > > > different HttpSessions and therefore you can not > > > share resources among them. > > > Can anyone help confirm this? or correct if I am > > > wrong? > > > > > > Thanks! > > > > > > > > > -- > > > To unsubscribe, e-mail: > > > <mailto:[EMAIL PROTECTED]> > > > For additional commands, e-mail: > > > <mailto:[EMAIL PROTECTED]> > > > > > > > ___________________________________________________________ > > Do You Yahoo!? -- Une adresse @yahoo.fr gratuite et en français ! > > Yahoo! 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