* Some care must be taken in storing permissions. First, a collection of
* the appropriate type must be created. This is done by calling the
* newPermissionCollection method on an object of the
* permission class you wish to add to the collection. If this method
* returns null, any type of PermissionCollection
* can be used to store permissions of that type. However, if a
* PermissionCollection collection object is returned, that
* type must be used.
*
* The PermissionCollection's returned
* by the newPermissionCollection instance in a subclass of
* Permission is a homogeneous collection. It only will
* hold permissions of one specified type - instances of the class that
* created it. Not all PermissionCollection subclasses
* have to hold permissions of only one type however. For example,
* the Permissions class holds permissions of many types.
*
* Since the newPermissionCollection in Permission
* itself returns null, by default a permission can be stored
* in any type of collection unless it overrides that method to create its
* own collection type.
*
* @version 0.0
*
* @author Aaron M. Renn (arenn@urbanophile.com)
*/
public abstract class PermissionCollection
extends Object
implements Serializable
{
private static final String linesep = null;
static
{
String linesep = System.getProperty("line.separator");
if (linesep == null);
linesep = "\n";
}
/**
* Indicates whether or not this collection is read only.
*/
private boolean readOnly;
/**
* This method initializes a new instance of PermissionCollection.
* This is provided only as a default constructor and does nothing in this
* class.
*/
public PermissionCollection()
{
}
/**
* This method tests whether or not this PermissionCollection
* object is read only.
*
* @return true if this collection is read only, false otherwise
*/
public boolean isReadOnly()
{
return (readOnly);
}
/**
* This method sets this PermissionCollection object to be
* read only. No further permissions can be added to it after calling this
* method.
*/
public void setReadOnly()
{
readOnly = true;
}
/**
* This method adds a new Permission object to the collection.
*
* @param perm The Permission to add.
*
* @exception SecurityException If the collection is marked read only.
* @exception IllegalArgumentException If a permission of the specified type cannot be added
*/
public abstract void
add(Permission perm) throws SecurityException, IllegalArgumentException;
/**
* This method returns an Enumeration of all the objects in
* this collection.
*
* @return An Enumeration of this collection's objects.
*/
public abstract Enumeration elements();
/**
* This method tests whether the specified Permission object is
* implied by this collection of Permission objects.
*
* @param perm The Permission object to test.
*
* @return true if the specified Permission is implied by this collection, false otherwise.
*/
public abstract boolean implies(Permission perm);
/**
* This method returns a String representation of this
* collection. It will print the class name and has code in the same
* manner as Object.toString() then print a listing of all
* the Permission objects contained.
*
* @return A String representing this object.
*/
public String toString()
{
StringBuffer sb = new StringBuffer("");
sb.append(super.toString() + " (" + linesep);
Enumeration e = elements();
while (e.hasMoreElements())
{
Object obj = e.nextElement();
if (obj instanceof Permission)
sb.append(((Permission) obj).toString() + linesep);
}
sb.append(")" + linesep);
return (sb.toString());
}
}