1. Example: RMI Program
How to write it

2. Program an ATM Machine
Allow the client to withdraw, deposit, transfer money to or from their account
Also allow to obtain the current balance
Some other stuff
ATM machine is the client
Bank with Account is the server

3. Write the code Write the Remote Interface, call it Account
Write the implementation: AccountImpl
Write the server: RegAccount
Write the client: AccountImpl
Stubs and skeletons will be generated

4. Account.java

5. Remarks Note that Account extends Remote
Every remote method in the interface throws a RemoteException
This interface is present on the server and on the client

6. AccountImpl.java

7. AccountImpl.java (ctd)

8. Remarks
Since this class is remote it must implement the UnicastRemote interface
The concrete methods from the remote interface all must throw a RemoteException
The rest is just POJ (Plain old Java)

9. Define the Server
Make an instance whose methods will be called by the client
Register this object with the registry
Note that it contains the main{} that defines the server
No remote exceptions here

10. RegAccount.java

11. Write the Client: AccountClient.java
Need a Security Manager (later)
Get a stub from the server by Naming.lookup()
Make the remote calls--here getName() and getBalance()
The URL parameter to the lookup routine returns the remote object it references
main(){} here is the client.

12. AccountClient.java

13. Running the Example ATM
Compile the java files: javac Account*.java
Create stub from AccountImpl: rmic AccountImpl
Start the registry: rmiregistry
Start the server: java RegAccount
Start the client: java AccountClient

14. What is Missing A Security Manager A Security Policy A Codebase
Compile and Execution commands that incorporate these
An appropriate deployment strategy

15. Security Manager
If your application only runs locally (sandbox) then there is no need for security
But RMI is designed to run on networks and the Internet
Hence the need for security
The Security Manager is a Java class that checks whether certain operations are permitted
Is available under java.lang.SecurityManager

16. Security Manager (ctd)
Checks permissions according to a security policy
Infractions of permissions cause a SecurityException
Set up by issuing:
System.setSecurityManager (new RMISecurityManager());
Enclose critical code in try block

17. Permissions Set by a security policy as written by the programmer
For purposes of testing a blanket granting of permissions can be issued:
permission java.security.AllPermission;
Then after deploying be a bit more restrictive:
grant{
permission java.net.SocketPermission “*: ”, “connect, accept, resolve”;
permission java.net.SocketPermission “*:80”, “connect”; };

18. Codebase
When starting the server indicate the download directory by means of a codebase property: For example
java -D Djava.rmi.server.codebase= xxxServ
This represents the URL location from which the stubs can be downloaded
Note the final slash “/” on the URL

19. Running the Client Need to include security with -D Start the Client:
java -Dsecurity.policy=sec.policy xxxClient
sec.policy needs a path
Do this for both server and client