privateaccesstest.java

《透视Java》的源码

package covertjava.visibility;

import java.awt.*;
import java.lang.reflect.Method;

import covertjava.chat.MainFrame;

/**
 * <p>Gives public access to private class members</p>
 * <p>Copyright: Copyright (c) 2004 Sams Publishing</p>
 * @author Alex Kalinovsky
 * @version 1.0
 */
public class PrivateAccessTest {

    public static void main(String[] args) throws Exception {
        System.out.println("Testing private access");
        Container container = createTestContainer();
        if (container.getLayout() instanceof BorderLayout) {
            BorderLayout layout = (BorderLayout)container.getLayout();
            Component center = getChild(layout, BorderLayout.CENTER);
            System.out.println("Center component = " + center);
        }
        else
            System.out.println("Container does not use BorderLayout");

    }

    public static Component getChild(BorderLayout layout, String key) throws Exception {
        Class[] paramTypes = new Class[]{String.class, boolean.class};
        Method method = layout.getClass().getDeclaredMethod("getChild", paramTypes);
        // Private methods are not accessible by default
        method.setAccessible(true);
        Object[] params = new Object[] {key, new Boolean(true)};
        Object result = method.invoke(layout, params);
        return (Component)result;
    }

    public static Container createTestContainer() throws Exception {
        MainFrame frame = new MainFrame(false);
        return frame.getContentPane();
    }
}