java - 如何从私有(private)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
        }
    }
}

我在程序中得到了一个 Outer 对象，如何使用反射在我的程序中提取innerPersonal。

Answer 1

由于您想要在 Outer 外部执行代码，因此不能使用 Outer.Inner.class 来引用您的 静态内部类它是 private，所以在这里我提出了一种方法，首先获取字段 personal 的值，然后调用 getClass()字段的返回值(假设它不是 null)，以最终访问此内部类，该内部类还允许访问其字段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);