带参数的Groovy模拟Java类

Question

I'm trying to use groovy's MockFor and proxyDelegateInstance to mock a java class with constructor parameters, but I can't seem to get it right. My Java class looks like:

class MyJavaClass {
   private MyObject myObj
   public MyJavaClass(MyObject myObj) {
      this.myObj = myObj;
   }
}

class MyGroovyTest {
    @Test
    void testMyJavaClass() {
        def mock = new MockFor(MyJavaClass)
        MyJavaClass mjc = new MyJavaClass()
        def mockProxy = mock.proxyDelegateInstance([mjc] as Object[])
        // if I pass mockProxy to anything, I get an error that a matching 
        // constructor could not be found. I've tried variations on the args 
        // to proxyDelegateInstance (such as using mjc as a single arg rather than 
        // an array of one element)
    }

}

Can I actually do this in groovy? And if so, how can I do it?

thanks, Jeff

Answer 1

The problem was that the class being mocked was a class and not an interface. In order to use the proxyDelegateInstance method, the an interface type needs to be used (or a groovy class). The proxy class is not actually of the MyJavaClass type but is a proxy and groovy's duck typing can handle that while Java cannot.

Answer 2

I can't tell you why your code above is not working, but there are several ways in Groovy to mock Java classes without using MockFor . For example, if you want to intercept all calls to the object, you can implement invokeMethod on the classes' metaClass, eg

class SomeJavaClass {
  // methods not shown
}

def instance = new SomeJavaClass()

instance.metaClass.invokeMethod = {String name, args ->
  // this will be called for all methods invoked on instance
}

Alternatively, if you simply want to provide an object that supports the method signatures of SomeJavaClass , you could use either a Map or an Expando with properties where:

• property names match method names
• proprerty values are closures that accept the same parameters as methods

If you can provide a bit more information about how the mock object is used, perhaps I can provide some more specific suggestions.