NPE when creating generic type

[pwfcurry]

public class TestClass {

  private final TestContainer<String> container;

  public TestClass(TestContainer<String> container) {
    this.container = container;
  }

  public class TestContainer<T> {

    private final T value;

    public TestContainer(T value) {
      this.value = value;
    }
  }

  public static void main(String[] args) {
    new JFixture().create(TestClass.class);
  }

}

Running the above code causes JFixture v2.5.1 to throw a NPE:

Exception in thread "main" java.lang.NullPointerException
    at com.flextrade.jfixture.utility.SpecimenType.<init>(SpecimenType.java:37)
    at com.flextrade.jfixture.utility.SpecimenType$3.<init>(SpecimenType.java:55)
    at com.flextrade.jfixture.utility.SpecimenType.withGenericContext(SpecimenType.java:55)
    at com.flextrade.jfixture.utility.ParameterUtils.convertPossibleGenericTypeToSpecimenType(ParameterUtils.java:50)

[richkeenan]

Java and generics. The bane of my life. Thanks @pwfcurry I'll take a look

[richkeenan]

Interestingly this works fine if TestContainer isn't an inner class

[richkeenan]

As suspected, this isn't an issue with Generics, it's an issue with the inner type. Your definition would cause a circular reference as TestClass requires TestContainer in the constructor but TestContainer implicitly takes an instance of TestClass because it's an inner class not marked as static.

You can't create an instance of TestClass whether you're using JFixture or not (unless you pass a null TestContainer in). If you modify TestContainer to be static JFixture will handle this correctly.

Maybe your simplified example is missing something else that your actual code has? I'm closing this issue but if you can reproduce it (and be able to create the class in 'regular' Java) please raise a new issue and I'll love to look into it.

[pwfcurry]

Oops, bad example. I still see the same problem when TestContainer is static, also when it's not an inner class.