Implementing Your Own Permission

The HighScorePermission Class

The HighScorePermission class defines the permission that TerrysGame needs to update the user's high score.

All permission classes should subclass from either java.security.Permission or java.security.BasicPermission. The basic difference between the two is that java.security.Permission defines more complex permissions that require names and actions. For example, a java.io.FilePermission extends from java.security.Permission, and requires a name (a filename), and actions allowed for that file (read/write/delete).

In contrast, java.security.BasicPermission defines simpler permissions that only require a name. For example, java.lang.RuntimePermission extends from java.security.BasicPermission and simply needs a name (like "exitVM"), which allows programs to exit the Java Virtual Machine.

Our HighScorePermission is a simple permission, and hence can be extended from java.security.BasicPermission.

Often, the method implementations in the BasicPermission class itself do not need to be overridden by its subclasses. That is the case with our HighScorePermission, so all we need to implement are the constructors, which just invoke the superclass constructors, as shown in the following:

import java.security.*;

public final class HighScorePermission extends BasicPermission {

    public HighScorePermission(String name)
    {
	super(name);
    }

    // note that actions is ignored and not used, but this constructor is still needed
    public HighScorePermission(String name, String actions) 
    {
	super(name, actions);
    }
}

Implementing Your Own Permission