Java安全管理器：如何指定“无权限”？

Question

The Java Security Manager allows to specify the permissions of some piece of code by defining clauses like:

... 
grant codebase http://foo.bar.com/test.jar {
   permission java.io.FilePermission "${user.dir}/*", "read,write"; }; 
...

in a policy file (default: <JRE_root>\\lib\\security . This grants code stemming from the given URL to read and write from/to the user's home directory (which is of course a no-no but that's another story).

But how do I define "NO permission", ie if that piece of code should NOT be allowed to read or write anywhere? I tried to specify:

...
  permission java.io.FilePermission "/-", ""; 
...

"/-" means the root directory and everything below it (ie everything) and the second argument "" was meant to signal "". But when I specify this like above I get a "token error". Apparently "" is not a valid "action". But how else does one then express "nothing" or "no permission" in these policy files?

Answer 1

Simply don't add any permissions lines. Classes will typically be given permissions to read their own code and resources. (See the API docs for java.io.FilePermission .)