有什么方法可以调用私有方法? [英] Any way to Invoke a private method?

问题描述

我有一个类，它使用 XML 和反射将 Object 返回给另一个类.

I have a class that uses XML and reflection to return Objects to another class.

通常这些对象是外部对象的子字段，但有时我想即时生成它.我试过这样的事情，但无济于事.我相信这是因为 Java 不允许您访问 private 反射方法.

Normally these objects are sub fields of an external object, but occasionally it's something I want to generate on the fly. I've tried something like this but to no avail. I believe that's because Java won't allow you to access private methods for reflection.

Element node = outerNode.item(0);
String methodName = node.getAttribute("method");
String objectName = node.getAttribute("object");

if ("SomeObject".equals(objectName))
    object = someObject;
else
    object = this;

method = object.getClass().getMethod(methodName, (Class[]) null);

如果提供的方法是private，它会失败并返回NoSuchMethodException.我可以通过使方法 public 或创建另一个类来派生它来解决它.

If the method provided is private, it fails with a NoSuchMethodException. I could solve it by making the method public, or making another class to derive it from.

长话短说，我只是想知道是否有办法通过反射访问 private 方法.

Long story short, I was just wondering if there was a way to access a private method via reflection.

推荐答案

您可以使用反射调用私有方法.修改贴出代码的最后一位:

You can invoke private method with reflection. Modifying the last bit of the posted code:

Method method = object.getClass().getDeclaredMethod(methodName);
method.setAccessible(true);
Object r = method.invoke(object);

有几个警告.首先，getDeclaredMethod 只会查找当前Class 中声明的方法，而不是从超类型继承的.因此，如有必要，请向上遍历具体的类层次结构.其次，SecurityManager 可以防止使用 setAccessible 方法.因此，它可能需要作为 PrivilegedAction 运行(使用 AccessController 或 Subject).

There are a couple of caveats. First, getDeclaredMethod will only find method declared in the current Class, not inherited from supertypes. So, traverse up the concrete class hierarchy if necessary. Second, a SecurityManager can prevent use of the setAccessible method. So, it may need to run as a PrivilegedAction (using AccessController or Subject).

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