Java在公共抽象超类上反映了非法访问异常

Question

I have been given an abstract class:

public abstract FooPACImpl {
    ...
}

And two autogenerated subclasses:

public replyTypeFooPAC extends FooPACImpl {
    ...
}
public requestTypeFooPAC extends FooPACImpl {
    ...
}

And an API for creating a network pattern (request/reply) that uses a request Type and a reply Type (A and B are expected to be auto-generated sub-classes of FooPACImpl like the above):

Replier<A, B> get_simple_replier (
    String topic, 
    Object<A> requestType, 
    Object<B> replyType) {...}

Requester<A, B> get_simple_requester (
    String topic, 
    Object<A> requestType, 
    Object<B> replyType) {...}

I pull the topic string, and the string names of the two types A and B from an XML stub:

<rr>
    <topic>MyReqRepTopic</topic>
    <reqtype>foo.bar.baz.myReqTypeFooPAC</reqtype>
    <replytype>foo.bar.baz.myReplyTypeFooPAC</replytype>
</rr>

Apparently, reflection in Java can't handle directly a "public abstract" super class?

FooPACImpl foopa = (FooPACImpl) Class.forName(reqtypeName).newInstance();

results in

java.lang.IllegalAccessException: Class foo.bar.fnorb.ServiceSupport \
    can not access a member of class foo.bar.baz.myReqTypeFooPAC with \
    modifiers "protected"

1) Why "with modifiers 'protected'"? FooPACImpl.getClass().getModifiers returns "public abstract"

2) Is this exception thrown because the class is abstract? or does it have to do with a possible constructor 'protected FooPACImpl () { };'?

3) And, is this even achievable? My understanding is that if you subclass AA with BB, you can use AA where a BB is expected, since BB will have anything that AA is expected to have (methods, fields, etc). Although, it's been awhile. I may be a bit hazy on the particulars of inheritance in java.

Thanks for any points/pointers, and a yes/no answer for #3 is sufficient. In the case of a 'no', hints to how it could be implemented without reflection. I do have access to the code generator templates for the autogenerated stuff, if that helps.

Answer 1

In the auto-generated sub-classes of FooPACImpl, there were two protected constructors:

protected myReqTypeFooPAC() {
    super(...);
}

protected myReqTypeFooPAC(boolean b) {
    super(..., b, ...); 
}

I was looking for the problem in the parent class, but it turned out to be the constructor thing. Changing those to public allowed the code to run as expected, which I can do either using reflection? or by changing the codegen templates...