how to load class dynamically from another location In RMI

FIRST I START WEB SERVER in (download directory) first window
1) ---> java NanoHTTPD 8080


then i start rmi registry ( second window)(RMIDIR Directory)
2) ---->RMIREGISTRY

then i start Server (Third window) (Server Directory)
3) ---->java -Djava.rmi.server.codebase=http://localhost:8080/ CalcServer
In serever directory

three file
calc.java(interface)
calcimpl.java
calcserver.java


4)In client directory......
javac -cp (path of server ) CalcClient.java
AND Run
java CalcClient

public class CalcClient { public static void main(String args[])throws RemoteException,NamingException { System.setProperty("java.security.policy","client.policy"); System.setSecurityManager(new SecurityManager()); Context nc=new InitialContext(); try { [b]Calc c = (Calc)nc.lookup("rmi://localhost/Calc_Service");[/b] System.out.println("3"); System.out.println("addition-->"+ c.add(10,10)); System.out.println("Subtraction-->"+ c.sub(5,6)); System.out.println("Multiplication-->"+ c.mul(5,3)); System.out.println("Division-->"+ c.div(10,5)); } catch(Exception e) { System.out.println("Error" + e ); } } }

it will give Exception class not found.....
If i manually copy Calc.class file in client directory....then program success fully run...........
so any body know HOW THE DYNAMIC DOWNLOADING is done.......

Howdy, Dashang!

Champion, I myself have never done this, but it looks like it is not complicated. Please take a look at Dynamic code downloading using RMI tutorial, which I think might be helpful.

Another tip I'd like to ask you, whenever you post code, please post it between the Code tags. It makes the post more readable!

You can edit your post to include these tags by clicking on the button.

Sir....thank you for reply.......
i have already...seen rmi dynamic class loading.............


but i am not finding the solution, .......please tell me how to do..........

Dashang,

Can you let me know the contents fetched from location http://localhost:8080/ CalcServer.

3) ---->java -Djava.rmi.server.codebase=http://localhost:8080/ CalcServer

The codebase property should return the jars/classes files which are downloaded to client system on remote object lookup.

CalcServer.java file..........

import java.rmi.*; import javax.naming.*; public class CalcServer { public static void main(String args[])throws RemoteException,NamingException { try { System.setProperty("java.security.policy","server.policy"); System.setSecurityManager(new SecurityManager()); System.out.println("Server Implemention"); CalcImpl c=new CalcImpl(); System.out.println("binding Server Implementation to naming registry "); Context nc=new InitialContext(); nc.bind("rmi:Calc_Service",c); System.out.println("Waiting for invocation from clients....."); } catch(Exception e) { System.out.println("Error" + e); } } }

The posted code shows:

Calc c = (Calc)nc.lookup("rmi://localhost/Calc_Service");

But the server was started as:
1) ---> java NanoHTTPD 8080

So which is it - default port 80 or changed port 8080

Bill

for RMI i need A WEB SERVER .......
so web server(java NanoHTTPD 8080 ) is started on 8080 port.......

Now from server machine codebase pass to WEBSERVER.....and it will BIND TO RMI REGISTRY.......

So my port is 8080.........

Dashang,

Can you implement small modification to class CalcSever

//Code to Replace
Context nc = new InitialContext(); nc.bind("rmi:Calc_Service", c);
//New Code
Naming.rebind("Calc_Service", c);
I tried the same locally it worked, hope the same is the case with you too.