Re: Yet another generics question: Needs unchecked conversion to conform to ...

From:
"Daniel Pitts" <googlegroupie@coloraura.com>
Newsgroups:
comp.lang.java.programmer
Date:
29 Dec 2006 23:22:45 -0800
Message-ID:
<1167463365.159629.211460@a3g2000cwd.googlegroups.com>
Michel T. wrote:

My first suggestion is not to use reflection.


I have to use reflection. This example is a very-reduced sample that
does not reflect the reality where this is required. I created this
simple class to show the warning.

If not, does BeanFactory<? extends Bean> work for you? (There is no
guarantee that the T in a subclass of BeanFactory is exactly Bean.)


I would not mind changing the return value of createFactory2 to

  BeanFactory<? extends Bean> createFactory2(String beanClass)

but I get the same warning.

Also, I tried the following but it does not compile (thus it must not
make sense either):

  public BeanFactory<? extends Bean> createFactory2(String beanClass)
throws Exception{

    Class<?> bc = Class.forName(beanClass);

    Class<? extends BeanFactory<? extends Bean>> bfc =
       bc.asSubclass(BeanFactory.class);

    Constructor<? extends BeanFactory<? extends Bean>> cstr =
      bfc.getConstructor(new Class[]{});

    return cstr.newInstance(new Object[]{});
  }

Alternatively, create a bean factory factory. (But stick with using a
Constructor rather than evil Class.newInstance.)


I must use reflection to instantiate the factory. Otherwise, I would
not be posting that question ;)

--
Michel T.


*Why* do you need to use reflection? I've found that in most
circumstances, you don't need to use it, even if you *think* you do.

Moving forward, assuming that you do indeed need to do it this way...
what is the exact warning you get? Can you post an sscce
<http://physci.org/codes/sscce/> that allows us to reproduce the
problem?

Anyway, good luck.

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