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Trail: Security Features in Java SE
Lesson: Quick Tour of Controlling Applets
Quick Tour of Controlling Applets
Observe Applet Restrictions
Set up a Policy File to Grant the Required Permission
Start Policy Tool
Grant the Required Permission
Save the Policy File
See the Policy File Effects
Home Page > Security Features in Java SE > Quick Tour of Controlling Applets
Observe Applet Restrictions

> The Java Plug-in uses a Security Manager to keep viruses from accessing your computer through an applet. No unsigned applet is allowed to access a resource unless the Security Manager finds that permission has been explicitly granted to access that system resource. That permission is granted by an entry in a policy file.

> `Here's the source code` for an applet named `WriteFile` that tries to create and to write to a file named `writetest` in the current directory. This applet will not be able to create the file unless it has explicit permission in a policy file.

> Type this command in your command window:

> >     appletviewer http://java.sun.com/docs/books/tutorial/security/tour1/examples/WriteFile.html

> Type this command on a single line, without spaces in the URL.

> You should see a message about a security exception, as shown in the following figure. This is the expected behavior; the system caught the applet trying to access a resource it does not have permission to access.

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