为什么我的小程序会抛出 AccessControlException? [英] Why is my applet throwing an AccessControlException?
问题描述
我正在尝试构建一个名为 game 的 Java 小程序，这是我以前从未做过的事情(我一直只是构建独立的应用程序).我的小程序在 Eclipse 中测试时运行良好，但是当我尝试将它放在我的网站上时，我在控制台中收到以下错误:
I am trying to build a Java applet, called game, which is something I have never done before (I've always just built standalone applications). My applet works fine when I test it in Eclipse, but when I try putting it on my website, I get the following error in the console:
java.lang.reflect.InvocationTargetException
at com.sun.deploy.util.DeployAWTUtil.invokeAndWait(DeployAWTUtil.java:116)
at sun.plugin2.applet.Plugin2Manager.runOnEDT(Plugin2Manager.java:3541)
at sun.plugin2.applet.Plugin2Manager.createApplet(Plugin2Manager.java:3072)
at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Plugin2Manager.java:1497)
at java.lang.Thread.run(Thread.java:680)
Caused by: java.security.AccessControlException: access denied (java.util.PropertyPermission user.dir read)
at java.security.AccessControlContext.checkPermission(AccessControlContext.java:374)
at java.security.AccessController.checkPermission(AccessController.java:546)
at java.lang.SecurityManager.checkPermission(SecurityManager.java:532)
at java.lang.SecurityManager.checkPropertyAccess(SecurityManager.java:1285)
at java.lang.System.getProperty(System.java:667)
at java.io.UnixFileSystem.resolve(UnixFileSystem.java:118)
at java.io.File.getAbsolutePath(File.java:501)
at game.<init>(game.java:117)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at java.lang.Class.newInstance0(Class.java:355)
at java.lang.Class.newInstance(Class.java:308)
at sun.plugin2.applet.Plugin2Manager$13.run(Plugin2Manager.java:3060)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:199)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:682)
at java.awt.EventQueue.access$000(EventQueue.java:85)
at java.awt.EventQueue$1.run(EventQueue.java:643)
at java.awt.EventQueue$1.run(EventQueue.java:641)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:652)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:296)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:211)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:196)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:188)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
Exception: java.lang.reflect.InvocationTargetException
它说 access denied (java.util.PropertyPermission user.dir read)，但我不知道它试图从用户的文件系统中读取某些内容.
It says access denied (java.util.PropertyPermission user.dir read), but I can't figure out where it's trying to read something off the user's file system.
它还说at game.，但我进入我的文件并在第114行向控制台输出了一条消息，但它从未被写入.然后我想可能它正在查看 public game() 中的第 117 行，所以我寻找它，它是鼠标事件侦听器的开始.对我来说，这将是 Java 需要获得读取权限的内容，所以我删除了所有内容，然后删除了所有导入以进行良好衡量.然后我清除了 Chrome 和 Java 的缓存并重试.同样的错误.
It also says at game.<init>(game.java:117), but I went into my file and made a message output to the console on line 114 and it never got written. I then figured that maybe it was looking at line 117 inside public game(), so I looked for that and it was the start of a listener for a Mouse event. It made sense to me that this would be something that Java would need permission to read, so I deleted all of it and then deleted all the imports for good measure. Then I cleared both Chrome and Java's caches and retried. Same error.
- 这是什么意思，我是否理解错误?
- 当它说第 117 行时，第 117 行是什么?
- 为什么会发生这种情况?
- 我该如何解决?
- 我如何才能防止将来发生这种情况?
作为参考，这里是public game()的代码:
For reference, here is the code for public game():
public game() throws MalformedURLException{
JPanel board = new chessboard();
board.setSize(320, 320);
board.setLocation(0, 0);
System.out.println("Got this far");
Piece wp1 = new Piece(wpawn, a2);
...
Piece bk = new Piece(bking, e8);
board.add(wp1);
...
board.add(bk);
wp1.setLocation(wp1.square.getPoint());
...
bk.setLocation(bk.square.getPoint());
add(board);
repaint();
addMouseListener(new MouseAdapter(){
public void mousePressed(MouseEvent evt){
for (int i = 0; i < 8; i++){
for (int j = 0; j < 8; j++){
if (squares[i][j].piece != null)
System.out.println(squares[i][j].getPointString() + ": " + squares[i][j].piece.type);
}
}
Point p = evt.getPoint();
if (0 < p.x && p.x < 319 && 0 < p.y && p.y < 319){
Square clicked = getSquare(p);
System.out.println("up: " + clicked.getPointString());
if (clicked.piece != null){
pickedUp = true;
pickedUpPiece = clicked.piece;
}
}
}
public void mouseReleased(MouseEvent evt){
if (pickedUp){
Point p = evt.getPoint();
if (0 < p.x && p.x < 319 && 0 < p.y && p.y < 319){
System.out.println("down: " + getSquare(p).getPointString());
movePiece(pickedUpPiece, getSquare(p).getColumn(), getSquare(p).getRow());
}
pickedUp = false;
}
else System.out.println("Not picked up");
}
});
}
推荐答案
堆栈跟踪的关键输出是:
The key output of the stack trace is:
at java.io.File.getAbsolutePath(File.java:501)
at game.<init>(game.java:117)
这意味着您的 game.java 文件，在第 117 行，正在对某些东西调用 getAbsolutePath().嵌入在浏览器中的 Java 小程序不允许访问本地文件系统.
This means that your game.java file, at line 117, is calling getAbsolutePath() on something. Java applets embedded in a browser are not permitted to access the local filesystem.
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