How Can I Invoke Private Methods Using Reflection in Java Despite Access Restrictions?

Utilizing Reflection to Invoke Private Methods

Despite Java's restriction on accessing private methods through reflection, there exists a solution to overcome this limitation. To invoke a private method via reflection, one can leverage the following approach:

Firstly, obtain the private method using getDeclaredMethod(String methodName) instead of getMethod(String methodName). This method allows access to both public and private methods declared within the current class.

Then, to circumvent the default access restriction on private methods, employ the setAccessible(boolean accessible) method to grant accessibility. By setting accessible to true, you override the protection settings and allow invocation of the private method.

Finally, invoke the private method using invoke(Object object, Object... args) with the desired object and any required arguments.

Here's an updated version of the code provided in the original question:

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

Caveats:

• getDeclaredMethod restricts access to methods declared within the current class, not inherited methods. Inherited methods require traversing the concrete class hierarchy.
• SecurityManager can potentially prevent the use of setAccessible. In such cases, consider running the code as a PrivilegedAction utilizing AccessController or Subject.

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