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/*
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* Copyright (c) 1997, 2006, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.security;
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import java.util.*;
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/**
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* Abstract class representing a collection of Permission objects.
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*
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* <p>With a PermissionCollection, you can:
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* <UL>
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* <LI> add a permission to the collection using the <code>add</code> method.
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* <LI> check to see if a particular permission is implied in the
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* collection, using the <code>implies</code> method.
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* <LI> enumerate all the permissions, using the <code>elements</code> method.
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* </UL>
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* <P>
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*
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* <p>When it is desirable to group together a number of Permission objects
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* of the same type, the <code>newPermissionCollection</code> method on that
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* particular type of Permission object should first be called. The default
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* behavior (from the Permission class) is to simply return null.
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* Subclasses of class Permission override the method if they need to store
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* their permissions in a particular PermissionCollection object in order
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* to provide the correct semantics when the
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* <code>PermissionCollection.implies</code> method is called.
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* If a non-null value is returned, that PermissionCollection must be used.
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* If null is returned, then the caller of <code>newPermissionCollection</code>
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* is free to store permissions of the
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* given type in any PermissionCollection they choose
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* (one that uses a Hashtable, one that uses a Vector, etc).
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*
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* <p>The PermissionCollection returned by the
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* <code>Permission.newPermissionCollection</code>
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* method is a homogeneous collection, which stores only Permission objects
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* for a given Permission type. A PermissionCollection may also be
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* heterogeneous. For example, Permissions is a PermissionCollection
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* subclass that represents a collection of PermissionCollections.
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* That is, its members are each a homogeneous PermissionCollection.
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* For example, a Permissions object might have a FilePermissionCollection
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* for all the FilePermission objects, a SocketPermissionCollection for all the
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* SocketPermission objects, and so on. Its <code>add</code> method adds a
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* permission to the appropriate collection.
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*
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* <p>Whenever a permission is added to a heterogeneous PermissionCollection
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* such as Permissions, and the PermissionCollection doesn't yet contain a
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* PermissionCollection of the specified permission's type, the
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* PermissionCollection should call
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* the <code>newPermissionCollection</code> method on the permission's class
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* to see if it requires a special PermissionCollection. If
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* <code>newPermissionCollection</code>
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* returns null, the PermissionCollection
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* is free to store the permission in any type of PermissionCollection it
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* desires (one using a Hashtable, one using a Vector, etc.). For example,
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* the Permissions object uses a default PermissionCollection implementation
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* that stores the permission objects in a Hashtable.
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*
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* <p> Subclass implementations of PermissionCollection should assume
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* that they may be called simultaneously from multiple threads,
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* and therefore should be synchronized properly. Furthermore,
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* Enumerations returned via the <code>elements</code> method are
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* not <em>fail-fast</em>. Modifications to a collection should not be
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* performed while enumerating over that collection.
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*
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* @see Permission
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* @see Permissions
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*
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*
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* @author Roland Schemers
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*/
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public abstract class PermissionCollection implements java.io.Serializable {
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private static final long serialVersionUID = -6727011328946861783L;
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// when set, add will throw an exception.
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private volatile boolean readOnly;
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/**
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* Adds a permission object to the current collection of permission objects.
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*
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* @param permission the Permission object to add.
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*
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* @exception SecurityException - if this PermissionCollection object
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* has been marked readonly
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* @exception IllegalArgumentException - if this PermissionCollection
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* object is a homogeneous collection and the permission
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* is not of the correct type.
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*/
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public abstract void add(Permission permission);
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/**
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* Checks to see if the specified permission is implied by
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* the collection of Permission objects held in this PermissionCollection.
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*
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* @param permission the Permission object to compare.
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*
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* @return true if "permission" is implied by the permissions in
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* the collection, false if not.
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*/
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public abstract boolean implies(Permission permission);
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/**
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* Returns an enumeration of all the Permission objects in the collection.
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*
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* @return an enumeration of all the Permissions.
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*/
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public abstract Enumeration<Permission> elements();
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/**
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* Marks this PermissionCollection object as "readonly". After
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* a PermissionCollection object
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* is marked as readonly, no new Permission objects can be added to it
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* using <code>add</code>.
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*/
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public void setReadOnly() {
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readOnly = true;
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}
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/**
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* Returns true if this PermissionCollection object is marked as readonly.
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* If it is readonly, no new Permission objects can be added to it
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* using <code>add</code>.
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*
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* <p>By default, the object is <i>not</i> readonly. It can be set to
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* readonly by a call to <code>setReadOnly</code>.
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*
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* @return true if this PermissionCollection object is marked as readonly,
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* false otherwise.
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*/
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public boolean isReadOnly() {
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return readOnly;
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}
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/**
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* Returns a string describing this PermissionCollection object,
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* providing information about all the permissions it contains.
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* The format is:
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* <pre>
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* super.toString() (
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* // enumerate all the Permission
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* // objects and call toString() on them,
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* // one per line..
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* )</pre>
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*
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* <code>super.toString</code> is a call to the <code>toString</code>
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* method of this
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* object's superclass, which is Object. The result is
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* this PermissionCollection's type name followed by this object's
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* hashcode, thus enabling clients to differentiate different
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* PermissionCollections object, even if they contain the same permissions.
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*
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* @return information about this PermissionCollection object,
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* as described above.
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*
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*/
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public String toString() {
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Enumeration<Permission> enum_ = elements();
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StringBuilder sb = new StringBuilder();
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sb.append(super.toString()+" (\n");
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while (enum_.hasMoreElements()) {
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try {
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sb.append(" ");
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sb.append(enum_.nextElement().toString());
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sb.append("\n");
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} catch (NoSuchElementException e){
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// ignore
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}
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}
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sb.append(")\n");
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return sb.toString();
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}
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}
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