首先,这是我第一次提出一个java问题所以我希望自己可以理解:-)提前感谢所有关注此事的人。
我有一个applet,我需要根据用户与applet的交互来加载类。我已经签署了applet,因此安全性不应成为问题(如果我理解正确的话)。我的所有文件都位于applet.jar中,其中包含一个名为p6applet的包,并且包中包含所有.class文件。 我使用以下代码来测试applet:
<APPLET
CODE="p6applet.Main.class"
ARCHIVE = applet.jar
WIDTH=0
HEIGHT=0>
</APPLET>
需要加载的类位于用户硬盘上。它需要导入一个接口,该接口位于包p6applet下的applet.jar文件中。此接口称为AlgorithmExecutable。
当我运行我的应用程序时,它执行以下代码,在发生错误后: 程序执行以下代码行时会发生错误:
className = ...;
try {
System.out.println("Test1");
URL[] urlClass = {new URL("file:/C:/.../")};
System.out.println("Test2");
ClassLoader cl = new URLClassLoader(urlClass);
System.out.println("Test3");
algorithmClass = cl.loadClass(className); //This is where the error occurs
System.out.println("Test4");
algorithm = (AlgorithmExecutable) algorithmClass.newInstance();
System.out.println("The " + className + " has been loaded.");
} catch (MalformedURLException ex) {
System.out.println("MalformedURLException: " + ex);
} catch (ClassNotFoundException ex) {
System.out.println("ClassNotFoundException: " + ex);
} catch (InstantiationException ex) {
System.out.println("InstantiationException: " + ex);
} catch (IllegalAccessException ex) {
System.out.println("IllegalAccessException: " + ex);
}
我收到以下错误:
Exception in thread "AWT-EventQueue-7" java.lang.NoClassDefFoundError: p6applet/AlgorithmExecutable
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClassCond(Unknown Source)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.access$000(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at p6applet.AlgorithmHandler.getAlgorithm(AlgorithmHandler.java:52)
at p6applet.AlgorithmInterface.actionPerformed(AlgorithmInterface.java:671)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(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.ClassNotFoundException: p6applet.AlgorithmExecutable
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
... 38 more
如果可以帮助查明问题,我的applet在netbeans applet viewer中运行正常。我怀疑问题是需要加载的文件无法成功导入AlgorithmExecutable接口。任何帮助将不胜感激。
答案 0 :(得分:2)
我认为主要问题是你没有安全权限来使用file://,即使applet已经签名并且给出了安全权限。据我所知,您需要访问本地服务器上的URL或类路径中的jar。这是一个复杂的问题。
http://www.securingjava.com/chapter-two/chapter-two-7.html