java.lang.reflect.InvocationTargetException：这是什么原因？

Question

I get the following exception when i try to run the applet :

java.lang.reflect.InvocationTargetException
at com.sun.deploy.util.DeployAWTUtil.invokeAndWait(Unknown Source)
at sun.plugin2.applet.Plugin2Manager.runOnEDT(Unknown Source)
at sun.plugin2.applet.Plugin2Manager.createApplet(Unknown Source)
at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.RuntimeException: java.lang.IllegalAccessException: Class sun.plugin2.applet.Plugin2Manager$12 can not access a member of class MyApplet with modifiers ""
at sun.plugin2.applet.Plugin2Manager$12.run(Unknown Source)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
    Caused by: java.lang.IllegalAccessException: Class sun.plugin2.applet.Plugin2Manager$12 can not access a member of class MyApplet with modifiers ""
at sun.reflect.Reflection.ensureMemberAccess(Unknown Source)
at java.lang.Class.newInstance0(Unknown Source)
at java.lang.Class.newInstance(Unknown Source)
... 9 more

Exception: java.lang.reflect.InvocationTargetException

Applet Code :

import javax.swing.*;
import java.awt.*;

class MyApplet extends JApplet {

public JFrame frame;
public JPanel panel;
public JButton button;

public void init() {
    frame = new JFrame();
    panel = new JPanel();
    button = new JButton("click me ");
    panel.setBackground(Color.RED);
    panel.add(button);
    frame.add(panel);
    frame.setSize(300,300);
    frame.setVisible(true);
}   
 }

HTML File :

<applet code="MyApplet" codebase="AppletPackage" archive="JAR.jar" height="800" width="800">

JAR.jar contains a package named AppletPackage that contains the class MyApplet. It also contains the automatically added manifest file.

what is the problem ?

Answer 1

An InvocationTargetException suggests that some reflective call failed. It appears that some Sun (Oracle) class is trying to use Reflection to access a class in your code.

Your class MyApplet has no public scope modifier. If you add it, I expect things will work, as this is what the exception is complaining about.

Caused by: java.lang.IllegalAccessException: Class sun.plugin2.applet.Plugin2Manager$12 can not access a member of class MyApplet with modifiers ""