Using Groovy MetaClass to overwrite Methods

Question

I have a POJO that uses a service to do something:

public class PlainOldJavaObject {

    private IService service;

    public String publicMethod(String x) {
          


        

Answer 1

What you have looks fine. I ran a slightly modified version on it on the groovy console webapp and it ran without issue. See for yourself using this code at http://groovyconsole.appspot.com/.

public interface IService {
    String callX(Object o);
}

public class PlainOldJavaObject {

    private IService service;

    public String publicMethod(String x) {
        return doCallService(x);
    }

    public String doCallService(String x) {
        if(service == null) {
            throw new RuntimeException("Service must not be null");
        }
        return service.callX(x);
    }
}

def pojo = new PlainOldJavaObject()
pojo.metaClass.doCallService = { String s ->
    "no service"
}
println pojo.publicMethod("arg")

What version of Groovy are you using. It could very well be a bug in Groovy in the metaclass implementation. The groovy language moves pretty quickly and the metaclass implementation changes from version to version.

Edit - Feedback from Comment:

The version of the groovy console webapp is 1.7-rc-1. So it looks like that version may work as you want it to. They are currently in RC2 so I expect it would be released soon. Not sure if what you are seeing is a bug or just a difference in how it works in the 1.6.x version.