Two Web App communicating problem

[Garg Divya]

Hi All,

Here i am using Apache Tomcat 6.0.16. I have 2 Web App Hello1 and Hello2 each having 2 servlet. The relevent content of first servlet is:

   
 public void init() throws ServletException {
       
    System.out.print("----------------This has to be print on start up-----------");

    this.getServletContext().setAttribute("AppAtt", "This is attribute for application");
    System.out.println("----------------Att has been set-----------");
     ServletContext con=this.getServletContext().getContext("/Hello1");
        System.out.println("This is First context"+con);
    }
 

And for secondnd servet is:

  
  public void init() throws ServletException {
        System.out.println("\nThis is 2ndservlet");
        ServletContext con=this.getServletContext().getContext("/Hello1");
        System.out.println("This is First context"+con);
    }
  

I had put load on start up value 1 and 2 for both servlets repectively. Here is relevent content of server.xml

  <!-- Access log processes all example.
             Documentation at: /docs/config/valve.html -->
        <!--
        <Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs"  
               prefix="localhost_access_log." suffix=".txt" pattern="common" resolveHosts="false"/>
        -->
	<Context antiJARLocking="true" 
docBase="C:\Documents and Settings\db2admin.SERVERDGFT1\My Documents\NetBeansProjects\Hello1\build\web" path="/Hello1"/>
      <Context antiJARLocking="true" 
docBase="C:\Documents and Settings\db2admin.SERVERDGFT1\My Documents\NetBeansProjects\Hello2\build\web" path="/Hello2"/>

</Host>
    </Engine>
  </Service>
</Server>
  

And here is output consol:

  Using CATALINA_BASE:   C:\tomcat\apache-tomcat-6.0.16
Using CATALINA_HOME:   C:\tomcat\apache-tomcat-6.0.16
Using CATALINA_TMPDIR: C:\tomcat\apache-tomcat-6.0.16\temp
Using JRE_HOME:        C:\Program Files\Java\jdk1.6.0_14
Feb 19, 2010 11:58:47 AM org.apache.catalina.core.AprLifecycleListener init
Feb 19, 2010 11:58:47 AM org.apache.coyote.http11.Http11Protocol init
INFO: Initializing Coyote HTTP/1.1 on http-8080
Feb 19, 2010 11:58:47 AM org.apache.catalina.startup.Catalina load
INFO: Initialization processed in 455 ms
Feb 19, 2010 11:58:48 AM org.apache.catalina.core.StandardService start
INFO: Starting service Catalina
Feb 19, 2010 11:58:48 AM org.apache.catalina.core.StandardEngine start
INFO: Starting Servlet Engine: Apache Tomcat/6.0.16
----------------This has to be print on start up---------------------------Att has been set-----------
This is First contextorg.apache.catalina.core.ApplicationContextFacade@641e9a

This is 2ndservlet
This is First contextnull
Feb 19, 2010 11:58:48 AM org.apache.catalina.core.StandardContext addApplicationListener
INFO: The listener "listeners.ContextListener" is already configured for this context. 
The duplicate definition has been ignored.
Feb 19, 2010 11:58:48 AM org.apache.catalina.core.StandardContext addApplicationListener
INFO: The listener "listeners.SessionListener" is already configured for this context. 
The duplicate definition has been ignored.
Feb 19, 2010 11:58:49 AM org.apache.coyote.http11.Http11Protocol start
INFO: Starting Coyote HTTP/1.1 on http-8080
Feb 19, 2010 11:58:49 AM org.apache.jk.common.ChannelSocket init
INFO: JK: ajp13 listening on /0.0.0.0:8009
Feb 19, 2010 11:58:49 AM org.apache.jk.server.JkMain start
INFO: Jk running ID=0 time=0/31  config=null
Feb 19, 2010 11:58:49 AM org.apache.catalina.startup.Catalina start
INFO: Server startup in 1125 ms  

Now please can anybody help me in finding out the reason of why i am not getting the context of first app(Hello1) in second app(Hello2)

This is 2ndservlet
This is First contextnull

It is coming as null. Any suggestion most welcome. Thanks in advance.

Regards
Divya garg.

[Ankit Garg]

Divyyyyy please check your private messages for some administrative matter...

[Ulf Dittmer]

From the javadocs of ServletContext.getContext:

In a security conscious environment, the servlet container may return null for a given URL.

In Tomcat you can get around this by setting the Context's crossContext attribute to true.

[Garg Divya]

Hi,

Thanks for your reply. It was quite helpful. But my requirement is little changed now. Using Servlet context i can not get the session synchronization between two app because of some security issues. Please can you suggest me the best way of getting session synchronization between two app.

Thanks,
Divya Garg

[Ulf Dittmer]

What do you mean by "session synchronization"?

[Garg Divya]

ok let me elaborate.

I have a link in my page. As i click on that link my application get an attribute from from other app running on same server. But that attribute is set on application level on other application. so now the problem is if a user(same session) try to access my application on different timing, he will get different value of attribute because that attribute is dynamic with time. But i want a unique value for a user.

So now i have decided that i will use a Map or Hashtable to store a session id as key and attribute as value. So that every user would get a unique attribute. This is my idea. Can you suggest me is there any drawback in my approach related to seurity or performance something.

Thanks,
Divya garg

[Ulf Dittmer]

So there will be one value for each user, and that value should be unique across different web apps running on the same server? Where does this value come from, and how often does it change? Could it be stored in the DB along with all the other user information, so that all web apps can get at it?

[Garg Divya]

Yes there will be a unique for every user, this is primary requirement and that value will be like timestamps which will change every second. It will finally be stored in database.

Thanks,
Divya Garg

[Garg Divya]

Hi,

Sorry for late reply. Actually today i have discussed things with my PM. My task is little extended. I can not work on session ids. What i have to perform now is if a user log in from another browser then he or she should be in same session as he was in previous browser on the same application.

I mean to say is that a user is access the page and that page have an attribute value which is dynamic with time. Now problem is if the same user access the same page(after some time) by typing URL path of that page on different browser then he should be getting the same attribute value as it was previously.

By default we we log in our application from another browser then it logged in other session. So is there any technique to perform it?. Any suggestion regarding this? Thanks in advance.

Regards,
Divya Garg

[William Brogden]

Sounds like you will have to implement your own "session" object that tracks the user state. Make it serializable and write it to a common file space or database using the user's unique key.

Bill

[Garg Divya]

Hi all,

Thanks to all for your reply. My previous task is finished. Now my task is little more extended. Now i have been instructed that one of my application is deployed on one machine and i have to access its context in another app deployed on another server. So i think now i will have to use JNDI.

Since i had done some work on EJB with JBoss where we use JNDI and we bind HomeInterface to JNDI logical name and by that name we access that Home Interface in the code.

Here is that JNDI Code:

   

java.naming.factory.initial=org.jnp.interfaces.NamingContextFactory
java.naming.factory.url.pkgs=org.jboss.naming:org.jnp.interfaces
java.naming.provider.url=[quote]localhost[/quote]


and client code is:

Context jndiContext = getInitialContext();
Object ref = jndiContext.lookup("CabinHomeRemote");
CabinHomeRemote home = (CabinHomeRemote)

 

Here we can give the ip(in place of localhost) of web server.

In the same way now i will have to bind the servlet context of on application to JNDI Logical name. And through that name i will access the servlet context in another app deployed on another server. But now the problem is I m not getting sufficient coding based help from anywhere. Please can anybody provide me any of type help on this topic. Thanks in advance.

Regards,
Divya Garg

[Ben Souther]

Out of curiosity..
Why are you spreading things out over multiple web applications?

This is one area where the servlet spec (I haven't finished the spec for 3.0 so this might have changed) is not very specific.
Not specific means that behavior tends to be different from app server to app server, meaning that your app is not going to be very portable.