Extend a generic class dynamically in Java

问题

I need to extend on runtime a class with a generic signature.

For example, the class to be extended is:

public class A<T> {}

I need to get this dynamically:

public class B extends A<String> {}

I cannot use Proxy because I need to add the obtained class to the ClassLoader. I'm trying with javassist but I have no idea of how make it in the correct way.

回答1:

If you know type only at runtime, then you will have to use casting. Like:

 class TokenCounterMapper 
    extends Mapper<Object, Object, Object, Object>{
     public void map(Object key, Object value, Context context){
    if (value instanceOf String){    
String castedString = (String)value;
        ...
        }
        }
        }

来源：https://stackoverflow.com/questions/16894571/extend-a-generic-class-dynamically-in-java