Connecting java with erlang using JInterface

Question

I am trying to connect to a erlang node with java but I get an error. To start erlang I used this command erl -sname db -setcookie erlang.

This is my java code:

import com.ericsson.otp.erlang.OtpConnection;
import com.ericsson.otp.erlang.OtpErlangObject;
import com.ericsson.otp.erlang.OtpPeer;
import com.ericsson.otp.erlang.OtpSelf;


public class ErlConnection {

    private static OtpConnection conn;
     public OtpErlangObject received;
     private final String peer;
     private final String cookie;

     public static void main(String []args){
         new ErlConnection("db","erlang");
     }

      public ErlConnection(String _peer, String _cookie) {
          peer = _peer;
          cookie = _cookie;
          connect();

           /*Do Calls to Rpc methods and then close the connection*/
          disconnect();

      }

      private void connect() {
       System.out.print("Please wait, connecting to "+peer+"....\n");

       String javaClient ="java";
       try {
         OtpSelf self = new OtpSelf(javaClient, cookie.trim());
         OtpPeer other = new OtpPeer(peer.trim());
         conn = self.connect(other);
         System.out.println("Connection Established with "+peer+"\n");
       }
       catch (Exception exp) {
         System.out.println("connection error is :" + exp.toString());
         exp.printStackTrace();
       }

     }

     public void disconnect() {
       System.out.println("Disconnecting....");
       if(conn != null){
         conn.close();
       }
       System.out.println("Successfuly Disconnected");
     }

}

It compiles fine but then I get a runtime error and I have no idea what it means

mirt@ubuntu:~/erlang/projekt$ javac -classpath "/usr/lib/erlang/lib/jinterface-1.6.1/priv/OtpErlang.jar:." ErlConnection.java 
mirt@ubuntu:~/erlang/projekt$ java ErlConnection
Please wait, connecting to db....
Exception in thread "main" java.lang.NoClassDefFoundError: com/ericsson/otp/erlang/OtpSelf
    at ErlConnection.connect(ErlConnection.java:33)
    at ErlConnection.<init>(ErlConnection.java:21)
    at ErlConnection.main(ErlConnection.java:15)
Caused by: java.lang.ClassNotFoundException: com.ericsson.otp.erlang.OtpSelf
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:335)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    ... 3 more

Please, can anyone give me a solution to my problem.

Answer 1

I believe the issue is that you need to include the Jinterface libraries when you run java to run your program with the -cp option again. Consider writing a shell script or batch file to handle launching everything.

I would also recommend using a build system like Maven or Gradle to manage dependencies like Jinterface and to handle building the Java program.