Back to index...

	/*
	* Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	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.
	*
	* <p>Most Permission objects also include an "actions" list that tells the actions
	* that are permitted for the object. For example,
	* for a {@code 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
	* {@code java.lang.RuntimePermission},
	* that don't need such a list; you either have the named permission (such
	* as "system.exit") or you don't.
	*
	* <p>An important method that must be implemented by each subclass is
	* the {@code 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.
	*
	* <P> 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 implements Guard, java.io.Serializable {

	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
	* {@code 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
	* {@code checkPermission} method doesn't allow access.
	*
	* @see Guard
	* @see GuardedObject
	* @see SecurityManager#checkPermission
	*
	*/
	public void checkGuard(Object object) throws SecurityException {
	SecurityManager sm = System.getSecurityManager();
	if (sm != null) sm.checkPermission(this);
	}

	/**
	* Checks if the specified permission's actions are "implied by"
	* this object's actions.
	* <P>
	* This must be implemented by subclasses of Permission, as they are the
	* only ones that can impose semantics on a Permission object.
	*
	* <p>The {@code 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.
	* <P>
	* Do not use the {@code equals} method for making access control
	* decisions; use the {@code 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.
	* <P>
	* The required {@code hashCode} behavior for Permission Objects is
	* the following:
	* <ul>
	* <li>Whenever it is invoked on the same Permission object more than
	* once during an execution of a Java application, the
	* {@code 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.
	* <li>If two Permission objects are equal according to the
	* {@code equals}
	* method, then calling the {@code hashCode} method on each of the
	* two Permission objects must produce the same integer result.
	* </ul>
	*
	* @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 {@code 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:
	*
	* <pre>
	* perm1 = new FilePermission(p1,"read,write");
	* perm2 = new FilePermission(p2,"write,read");
	* </pre>
	*
	* both return
	* "read,write" when the {@code 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 {@code 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.
	*/

	public PermissionCollection newPermissionCollection() {
	return null;
	}

	/**
	* 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 + "\")";
	}
	}
	}

Back to index...