Fields from type T

Question

I want to get all the fields and it's values from an object of type T. Say I have:

public class Start {

    public void startMethod(){
        Main<GenericType> main = new Main<>();
        main.work(new GenericType());
    }

}

Then there's class Main, where I want the fields of GenericType:

public class Main<T> {

    public void work(T t){
        // Is there a way to get t's fields and values?
    }

}

Reflection. Try http://stackoverflow.com/questions/2989560/how-to-get-the-fields-in-an-object-via-reflection — Balwinder Singh, Oct 08 '15 at 05:12
T can be of any type ? ... or can't you declare an interface `` so that you can access getter methods from that interface ? — Pras, Oct 08 '15 at 05:13
You need to explain the background of what you are trying to do. In many situations you can avoid reflection, and you should if at all possible. — Paul Boddington, Oct 08 '15 at 05:17
@BalwinderSingh's answer helped me with my problem. I posted as minimal code as possible because the main problem is a *bit* bigger than the one I posted. Thank you all for your help. — Washington A. Ramos, Oct 08 '15 at 05:32

score 0 · Answer 1 · answered Oct 08 '15 at 05:17

0

First,you need to get Class of T,then through reflection ,you can get all fields.

abstract class A<T> {  
    Class<T> clazz;  
    void doGetClass() {  
        Type genType = this.getClass().getGenericSuperclass();  
        Type[] params = ((ParameterizedType) genType).getActualTypeArguments();  
        this.clazz = (Class<T>) params[0];  
    }
}

but you must instantiate the generic type ,like this,instantiate T to String:

class B extends A<String>{  
}

then

B b = new B();  
b.doGetClass();// b.clazz is String.class

answered Oct 08 '15 at 05:17

BlackJoker

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You seem to be complicating things a bit... Just doing `t.getClass()` will give the class object in OP's case... – Codebender Oct 08 '15 at 05:23
You cannot create an instance of generic type using `new T()`,so the object `t` cannot be instantiated – BlackJoker Oct 08 '15 at 05:38
He is passing the `t` parameter to the method... So you will already have an object of type `T` – Codebender Oct 08 '15 at 05:39
`t` is created by `new GenericType()` which will not work. – BlackJoker Oct 08 '15 at 06:06

score 0 · Accepted Answer · answered Oct 08 '15 at 05:39

Following @BalwinderSingh's answer I came to this:

public void work(T t){
    for(Field f : t.getClass().getDeclaredFields()){
        try {
            f.setAccessible(true);

            String name = f.getName();
            Object value = f.get(object);


        }catch(Exception e){
            e.printStackTrace();
        }
    }
}

It was simpler than I though at the beginning. Thank you all.

Fields from type T

2 Answers2