在JApplet中调用getParameter（）时发生InvocationTargetException

Question

我有一个Java 7中的JApplet，每次我想在浏览器中启动它时，我都会从JApplet的getParameter() InvocationTargetException中收到一个InvocationTargetException 。 这是我的堆栈跟踪：

java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
    at com.sun.deploy.uitoolkit.impl.awt.AWTAppletAdapter.runOnEDTAndWait(Unknown Source)
    at com.sun.deploy.uitoolkit.impl.awt.AWTAppletAdapter.instantiateApplet(Unknown Source)
    at sun.plugin2.applet.Plugin2Manager.initAppletAdapter(Unknown Source)
    at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.reflect.InvocationTargetException
    at com.sun.deploy.uitoolkit.impl.awt.OldPluginAWTUtil.invokeAndWait(Unknown Source)
    ... 5 more
Caused by: java.lang.NullPointerException
    at java.applet.Applet.getParameter(Unknown Source)
    at TicTacToe.TicTacToeAppletView.<init>(TicTacToeAppletView.java:34)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
    at java.lang.reflect.Constructor.newInstance(Unknown Source)
    at java.lang.Class.newInstance0(Unknown Source)
    at java.lang.Class.newInstance(Unknown Source)
    at com.sun.deploy.uitoolkit.impl.awt.AWTAppletAdapter$1.run(Unknown Source)
    at java.awt.event.InvocationEvent.dispatch(Unknown Source)
    at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
    at java.awt.EventQueue.access$000(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(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)

我的HTML文件如下所示：

<applet code="TicTacToe/TicTacToeAppletView.class" width="400" height="400">
<param name=Size value="4">
</applet>

在与HTML File相同的文件夹中，有一个名为TicTacToe的文件夹，其中包含所有必需的类文件（当然，否则，我会得到ClassNotFoundException ）。

如果我不使用getParameter（），它会很好地工作。 使用此方法的Java代码如下所示：

String s = getParameter("Size");

那么到底是什么造成了这么多麻烦呢？

Answer 1

参数名称Size不应该用引号引起来吗？

<param name="Size" value="4">

有关使用参数的更多信息，请查看“ 定义和使用Applet参数”教程