如何从私有静态内部类访问变量

Question

我有一个这样的类结构:

public class Outer{
    private Outer.Inner personal;
    public Outer(){
        //processing.
        //personal assigned value
    }
    ........
    private static class Inner {
        private final Set<String> innerPersonal;
        Inner(){
             innerPersonal=new HashSet<>();
             //populate innerPersonal
        }
    }
}

我在程序中得到一个Outer对象，我如何提取innerPersonal在我的程序，使用反射。

Answer 1

当你想在Outer之外执行代码时，你不能使用Outer.Inner.class来引用你的static inner class，因为它是private，所以在这里我提出一种方法，它将简单地首先获得字段personal的值，然后在字段的返回值上调用getClass()(假设它不是null)最终访问这个inner class，它允许访问它的字段innerPersonal。

Outer outer = ...
// Get the declared (private) field personal from the public class Outer
Field  personalField = Outer.class.getDeclaredField("personal");
// Make it accessible otherwise you won't be able to get the value as it is private
personalField.setAccessible(true);
// Get the value of the field in case of the instance outer
Object personal =  personalField.get(outer);
// Get the declared (private) field innerPersonal from the private static class Inner
Field  innerPersonalField = personal.getClass().getDeclaredField("innerPersonal");
// Make it accessible otherwise you won't be able to get the value as it is private
innerPersonalField.setAccessible(true);
// Get the value of the field in case of the instance personal
Set<String> innerPersonal = (Set<String>)innerPersonalField.get(personal);

Answer 2

@Retention(RetentionPolicy.RUNTIME)
    public @interface Factory {
            Class<?> value();
    }

---

public class Outer{
    private Outer.Inner personal;
    public Outer(){
        //processing.
        //personal assigned value
    }
    @Factory(SomeType.class)
    private static class Inner {
        public final Set<String> innerPersonal;
        Inner(){
             innerPersonal=new HashSet<>();
             //populate innerPersonal
        }
    }    

 }

---

Outer o = new Outer();
Object r = o.getClass().getAnnotationsByType(Factory.class);

---