An Erlang-Java Interop Demo - executable summary

erlang-java-interop-demo.sh

#!/bin/bash -x
#######################################################################
#
# Demo of Erlang IDL, as applied to property testing of Java code.

# We'll need Triq.
git clone git://github.com/krestenkrab/triq.git
(cd triq && ./rebar compile)

ERL_ROOT=`erl -noshell -eval 'io:format("~s\n", [code:root_dir()]), init:stop().'`


# Let's define an interface:
cat > foo.idl <<EOF
interface Foo {
  string quuxinate(in string s);
};
EOF

# Compile the interface:
erlc '+{be,java}' foo.idl

# Now for some implementation:
cat > FooImpl.java <<EOF
public class FooImpl extends _FooImplBase {
  public String quuxinate(String s) {
    int[] stats = new int[256];
    for (int i=0; i<s.length(); i++) {
      char c =  s.charAt(i);
      if (c<255 && ++stats[c] >= 3) throw new RuntimeException("WTF");//return s;
    }
    return new StringBuilder(s).reverse().toString();
  }

  /** The request environment is exposed for error handling reasons. */
  public com.ericsson.otp.ic.Environment getEnv() {
     return _env;
  }
}
EOF

cat > FooServer.java <<EOF
public class FooServer {
  // The following is based on the program in lib/ic/examples/java-client-server/server.java
  static java.lang.String snode = "javaserver";
  static java.lang.String cookie = "xyz";

  public static void main(String[] args) throws java.io.IOException, com.ericsson.otp.erlang.OtpAuthException {

    com.ericsson.otp.erlang.OtpServer self = new com.ericsson.otp.erlang.OtpServer(snode, cookie);

    System.err.print("Registering with EPMD...");
    boolean res = self.publishPort();
    if (!res) throw new RuntimeException("Node name was already taken.");
    System.err.println("done");

    do {
      try {
        com.ericsson.otp.erlang.OtpConnection connection = self.accept();
        System.err.println("Incoming connection.");
        try {
          handleConnection(connection);
        } catch (Exception e) {
          System.err.println("Server terminated: "+e);
        } finally {
          connection.close();
          System.err.println("Connection terminated.");
        }
      } catch (Exception e) {
        System.err.println("Error accepting connection: "+e);
      }
    } while (true);
  }

  static void handleConnection(com.ericsson.otp.erlang.OtpConnection connection) throws Exception {
    while (connection.isConnected() == true) {
      FooImpl srv = new FooImpl();
      com.ericsson.otp.erlang.OtpInputStream request= connection.receiveBuf();
      try {
        com.ericsson.otp.erlang.OtpOutputStream reply = srv.invoke(request);
        if (reply != null) {
          connection.sendBuf(srv.__getCallerPid(), reply);
        }
      } catch (Exception e) {
	System.err.println("Server exception: "+e);
	e.printStackTrace(System.err);
        handleException(e, connection, srv.getEnv());
      }
    }
  }

  static void handleException(Exception e, com.ericsson.otp.erlang.OtpConnection connection, com.ericsson.otp.ic.Environment env) throws Exception {
    // Write exception reply:
    com.ericsson.otp.erlang.OtpOutputStream err_reply = new com.ericsson.otp.erlang.OtpOutputStream();
    err_reply.write_tuple_head(2);
    err_reply.write_any(env.getSref());
    err_reply.write_tuple_head(2);  // Construct return value {error, ErrorText}
    err_reply.write_atom("error");
    err_reply.write_string(e.toString());
    connection.sendBuf(env.getScaller(), err_reply);
  }

}
EOF

# Compile Java parts:
echo "ERL_ROOT is $ERL_ROOT"
IC_JAR=`ls -1 $ERL_ROOT/lib/ic-*/priv/ic.jar`
JI_JAR=`ls -1 $ERL_ROOT/lib/jinterface-*/priv/OtpErlang.jar`
CLASSPATH=".:$IC_JAR:$JI_JAR"
javac -classpath "$CLASSPATH" *.java
echo "CLASSPATH is $CLASSPATH"

# Run the server:
echo "Starting the server..."

# To run manual tests, use these lines:
#java -classpath "$CLASSPATH" FooServer ; read
#exit 0

# To run automatic tests, use these lines:
java -classpath "$CLASSPATH" FooServer 2>> server.log &
JAVAPID=$!
echo "JAVAPID=$JAVAPID"

# The server should now be registered with epmd:
sleep 1; echo; epmd -names ; echo

# On the Erlang side, first a simple test:
cat <<EOF | erl -sname tester -setcookie xyz
{ok,Host}=inet:gethostname(),
JavaServer = {dummy, list_to_atom("javaserver@"++Host)},
gen_server:call(JavaServer, {quuxinate, "Testing, 1-2-3"}).
init:stop().
EOF

# Then a real property test:
cat > test.erl <<EOF
-module(test).
-include_lib("triq/include/triq.hrl").
-export([main/0]).

prop_reverse(JavaServer) ->                  % The property
  ?FORALL(S, ascii_string(),
      gen_server:call(JavaServer, {quuxinate, S})
      == lists:reverse(S)).

ascii_string() ->                            % A data generator
  list(choose(0,127)).

main() ->
  {ok,Host}=inet:gethostname(),
  JavaServer = {dummy, list_to_atom("javaserver@"++Host)},

  triq:check(prop_reverse(JavaServer), 100), % Do the magic
  init:stop().                               % Shut down cleanly
EOF

erlc -I triq/include -pa triq/ebin test.erl

# Run it:
erl -noshell -sname tester -setcookie xyz -pa triq/ebin -run test main



#----------
# Cleanup:
kill $JAVAPID