[Jython-users] Java typecasts in Jython?

[Johannes E. <joh...@eb...>]

Hello community,

I would like to know how to handle Java typecasts in Jython. For example, I
have a Java class ProxyGenerator that I want to use in Python. It has (a.a.)
the method newInstance. From Java you would use the class as follows ( just
notice the typecast):

agencyProxy = (IAgentSystem)ProxyGenerator.newInstance(IAgentSystem.class,
                        agencyAddress.generateAgentSystemId(),
agencyAddress);

I can't just do

agencyProxy = ProxyGenerator.newInstance(IAgentSystem.class,
                        agencyAddress.generateAgentSystemId(),
agencyAddress)


in Jython because I get the error that None has no attribute 'newInstance'.
Instead, I have created a wrapper class GetAgency in Java

public class GetAgency {

  public static IAgentSystem getAgency(GrasshopperAddress agencyAddress) {
    return (IAgentSystem) ProxyGenerator.newInstance(IAgentSystem.class,
                        agencyAddress.generateAgentSystemId(),
agencyAddress);
  }
}

Now, it works if I do the following in Jython:

agencyProxy = GetAgency.getAgency(agencyAddress)


Does that mean that I always have to write a wrapper in Java to do the
typecast and call this wrapper from Jython?


Also, I have this problem when I want to write a class (an agent) in Jython
that is used by a Java system (an agency in my case): The init method of the
agent class is used for startup parameters. However, the parameters are
contained in an java.lang.Object array (Object[]) and must be casted back to
their original types. If I write the agent class in Java, it looks like
this:


  public void init(Object[] args){
    try{
      queryNr     = ((Integer)args[1]).intValue();
      path = new ArrayList();
      Object[] pathArray= (Object[])args[0];
      for (int i=0;i<pathArray.length;i++) path.add(pathArray[i]);
      finalDestination= (String)args[2];
    }catch(Exception exc){
      System.out.println("Exception in agent creation: "+exc.toString());
    }


  }


How do I do this in Jython? Do I also have to write Java wrapper
classes/methods for each type cast? I suppose that I have to bother about
the casts because I don't think that Jythonc will get the things right
automatically and it will probably confuse the JRE running the agency.



Any help would be great :)


Regards

Johannes