Why do I receive an error when connecting to a Java RMI Registry if it was created in a class which was called in MATLAB?

I have written a Java class that either uses an existing RMI registry, or creates one. See the following Java code snippet:

 try {

reg = LocateRegistry.getRegistry(1099);

reg.list();

 } catch (Exception e1) {

reg = LocateRegistry.createRegistry(1099);

 }

See the files RMIExample.java and IRMIExample.java below for full source code.

When I instantiate the first object of this class in MATLAB:

>> a = tmw.dta.RMIExample

a =

RMIExample[UnicastServerRef [liveRef: [endpoint:[172.16.59.161:4086](local),objID:[-212c6059:11db4762d8e:-7fff, 4536923814734999922]]]]

the RMI registry is created, but then when I create a second object (which should thus connect to the registry created by the first instantiation) I receive a Java exception:

>> b = tmw.dta.RMIExample

 java.rmi.ServerException: RemoteException occurred in server thread; nested exception is: 

 java.rmi.UnmarshalException: error unmarshalling arguments; nested exception is: 

 java.lang.ClassNotFoundException: tmw.dta.IRMIExample (no security manager: RMI class loader disabled)

b =

RMIExample[UnicastServerRef [liveRef: [endpoint:[172.16.59.161:4086](local),objID:[-212c6059:11db4762d8e:-7ffe, -8406764515259456100]]]]

When I create two instances of this class outside MATLAB, or when I first manually start the RMI registry, I do not receive this Java exception.

Answer 1

[MathWorks Support Team]

You need to start a security manager before creating the RMI registry:

URL url = getClass().getResource("client.policy");

System.setProperty("java.security.policy", url.toString()); 

if (System.getSecurityManager() == null) {

      System.setSecurityManager(new RMISecurityManager());

}

It is very important that the file client.policy can be found (otherwise MATLAB will crash), therefore in this example we assume that you include it in your JAR-file (or Java classpath). This ensures that it can be found using getClass().getResource. The contents of client.policy should resemble:

 grant {

   permission java.security.AllPermission;

 };

You can apply stricter policies if your application requires it.

The attached file RMIExampleWithSecMan.java shows a fully working example class.