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*
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package java.security;
/**
* Abstract class for representing access to a system resource.
* All permissions have a name (whose interpretation depends on the subclass),
* as well as abstract functions for defining the semantics of the
* particular Permission subclass.
*
* Most Permission objects also include an "actions" list that tells the actions
* that are permitted for the object. For example,
* for a java.io.FilePermission object, the permission name is
* the pathname of a file (or directory), and the actions list
* (such as "read, write") specifies which actions are granted for the
* specified file (or for files in the specified directory).
* The actions list is optional for Permission objects, such as
* java.lang.RuntimePermission,
* that don't need such a list; you either have the named permission (such
* as "system.exit") or you don't.
*
*
An important method that must be implemented by each subclass is
* the implies method to compare Permissions. Basically,
* "permission p1 implies permission p2" means that
* if one is granted permission p1, one is naturally granted permission p2.
* Thus, this is not an equality test, but rather more of a
* subset test.
*
*
Permission objects are similar to String objects in that they
* are immutable once they have been created. Subclasses should not
* provide methods that can change the state of a permission
* once it has been created.
*
* @see Permissions
* @see PermissionCollection
*
*
* @author Marianne Mueller
* @author Roland Schemers
*/
public abstract class Permission
{
private static final long serialVersionUID= -5636570222231596674L;
private String name;
/**
* Constructs a permission with the specified name.
*
* @param name name of the Permission object being created.
*
*/
public Permission(String name)
{
this.name= name;
}
/**
* Implements the guard interface for a permission. The
* SecurityManager.checkPermission method is called,
* passing this permission object as the permission to check.
* Returns silently if access is granted. Otherwise, throws
* a SecurityException.
*
* @param object the object being guarded (currently ignored).
*
* @throws SecurityException
* if a security manager exists and its
* checkPermission method doesn't allow access.
*
* @see Guard
* @see GuardedObject
* @see SecurityManager#checkPermission
*
*/
public void checkGuard(Object object) throws SecurityException
{
}
/**
* Checks if the specified permission's actions are "implied by"
* this object's actions.
*
* This must be implemented by subclasses of Permission, as they are the
* only ones that can impose semantics on a Permission object.
*
*
The implies method is used by the AccessController to determine
* whether or not a requested permission is implied by another permission that
* is known to be valid in the current execution context.
*
* @param permission the permission to check against.
*
* @return true if the specified permission is implied by this object,
* false if not.
*/
public abstract boolean implies(Permission permission);
/**
* Checks two Permission objects for equality.
*
* Do not use the equals method for making access control
* decisions; use the implies method.
*
* @param obj the object we are testing for equality with this object.
*
* @return true if both Permission objects are equivalent.
*/
public abstract boolean equals(Object obj);
/**
* Returns the hash code value for this Permission object.
*
* The required hashCode behavior for Permission Objects is
* the following:
*
* - Whenever it is invoked on the same Permission object more than
* once during an execution of a Java application, the
*
hashCode method
* must consistently return the same integer. This integer need not
* remain consistent from one execution of an application to another
* execution of the same application.
*
- If two Permission objects are equal according to the
*
equals
* method, then calling the hashCode method on each of the
* two Permission objects must produce the same integer result.
*
*
* @return a hash code value for this object.
*/
public abstract int hashCode();
/**
* Returns the name of this Permission.
* For example, in the case of a java.io.FilePermission,
* the name will be a pathname.
*
* @return the name of this Permission.
*
*/
public final String getName()
{
return name;
}
/**
* Returns the actions as a String. This is abstract
* so subclasses can defer creating a String representation until
* one is needed. Subclasses should always return actions in what they
* consider to be their
* canonical form. For example, two FilePermission objects created via
* the following:
*
*
* perm1 = new FilePermission(p1,"read,write");
* perm2 = new FilePermission(p2,"write,read");
*
*
* both return
* "read,write" when the getActions method is invoked.
*
* @return the actions of this Permission.
*
*/
public abstract String getActions();
/**
* Returns an empty PermissionCollection for a given Permission object, or null if
* one is not defined. Subclasses of class Permission should
* override this if they need to store their permissions in a particular
* PermissionCollection object in order to provide the correct semantics
* when the PermissionCollection.implies method is called.
* If null is returned,
* then the caller of this method is free to store permissions of this
* type in any PermissionCollection they choose (one that uses a Hashtable,
* one that uses a Vector, etc).
*
* @return a new PermissionCollection object for this type of Permission, or
* null if one is not defined.
*/
/**
* Returns a string describing this Permission. The convention is to
* specify the class name, the permission name, and the actions in
* the following format: '("ClassName" "name" "actions")', or
* '("ClassName" "name")' if actions list is null or empty.
*
* @return information about this Permission.
*/
public String toString()
{
String actions= getActions();
if ((actions == null) || (actions.length() == 0))
{ // OPTIONAL
return "(\"" + getClass().getName() + "\" \"" + name + "\")";
}
else
{
return "(\"" + getClass().getName() + "\" \"" + name + "\" \"" + actions + "\")";
}
}
}