AccessControlException in Java Applet

Question

I have created an applet within a web page, but whenever I run it, I get this:

Exception in thread "Thread-13" java.security.AccessControlException: access denied ("java.io.FilePermission" "defensebg.png" "read")
    at java.security.AccessControlContext.checkPermission(Unknown Source)
    at java.security.AccessController.checkPermission(Unknown Source)
    at java.lang.SecurityManager.checkPermission(Unknown Source)
    at java.lang.SecurityManager.checkRead(Unknown Source)
    at java.io.File.canRead(Unknown Source)
    at javax.imageio.ImageIO.read(Unknown Source)
    at Defense.run(Defense.java:63)
    at java.lang.Thread.run(Unknown Source)

How do I fix this?

Answer 1

Since I know a little about your applet and am convinced these images are an inherent part of the application, I will take a different tack to paulms4.

Forget the File instances. They are neither workable for this, nor necessary. Only a trusted applet can access a File, but even then, the only place that an applet can establish a File is one that points to locations on the file-system of the user's PC. Obviously the images for your applet are not available that way (OK - they might be in a browser cache, but that is no use to us).

It would be more typical (& easier) to access applet resource by URL. An URL can be established relative to the code-base or document-base of the applet. If the images are actually inside a Jar, they become an embedded resource - see the info. page as to how to gain an URL.

Most of the methods in the J2SE that load a 'read only' resource will accept File, URL or InputStream. I use URL most often for the generic utility of it. An URL can represent a web resource, a file on the local file system, or a resource buried deep inside a Jar file (whether or on the web or the local file-system).

Answer 2

Q: How do I fix this?

A: Uh - don't try to read files on the client PC from an applet?

Or read about "Policy files":

• http://docs.oracle.com/javase/tutorial/security/tour1/wstep2.html

Java applets run in a secure "sandbox". This is by design - for the end-user's safety:

• http://docs.oracle.com/javase/tutorial/security/tour1/step1.html