Groovy特性支持Java联合编译吗？

Question

I am quite excited about traits in Groovy, but I can't get them to work at all with joint compilation. Example:

Bird.groovy:

trait FlyingAbility {
  String fly() { "I'm flying!" }
}

class Bird implements FlyingAbility {}

JavaClass.java:

public class JavaClass {
  public static void main(String[] args) {
    Bird b = new Bird();
    // FlyingAbility f = new Bird();
  }
}

The generated stub is:

public class Bird
  extends java.lang.Object  implements
    FlyingAbility {
;
public  groovy.lang.MetaClass getMetaClass() { return (groovy.lang.MetaClass)null;}
public  void setMetaClass(groovy.lang.MetaClass mc) { }
public  java.lang.Object invokeMethod(java.lang.String method, java.lang.Object arguments) { return null;}
public  java.lang.Object getProperty(java.lang.String property) { return null;}
public  void setProperty(java.lang.String property, java.lang.Object value) { }
}

This results in the java compiler complaining that FlyingAbility is not defined (and is not an interface). I find it hard to believe this is not supported: am I missing something?

Answer 1

I find it hard to believe this is not supported: am I missing something?

You haven't indicated which version of Groovy you are using and there may have been a bug at some point, but the answer to your question is that it is supported.

See the project at https://github.com/jeffbrown/traitandjava . The relevant files are:

https://github.com/jeffbrown/traitandjava/blob/master/src/main/groovy/demo/FlyingAbility.groovy

https://github.com/jeffbrown/traitandjava/blob/master/src/main/groovy/demo/Bird.groovy

https://github.com/jeffbrown/traitandjava/blob/master/src/main/groovy/demo/BirdKeeper.java

https://github.com/jeffbrown/traitandjava/blob/master/src/test/groovy/demo/BirdKeeperSpec.groovy

That project is using Groovy 2.4.4 and it all works.

I hope that helps.