jdk/src/share/classes/java/security/Permission.java
changeset 2 90ce3da70b43
child 2172 2e7377d894db
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/share/classes/java/security/Permission.java	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,231 @@
+/*
+ * Copyright 1997-2003 Sun Microsystems, Inc.  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.  Sun designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.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</code> 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</code>,
+ * 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</code> 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</code> 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</code> 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</code> 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</code> method for making access control
+     * decisions; use the <code>implies</code> 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</code> behavior for Permission Objects is
+     * the following: <p>
+     * <ul>
+     * <li>Whenever it is invoked on the same Permission object more than
+     *     once during an execution of a Java application, the
+     *     <code>hashCode</code> 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. <p>
+     * <li>If two Permission objects are equal according to the
+     *     <code>equals</code>
+     *     method, then calling the <code>hashCode</code> 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</code>,
+     * 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</code> 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</code> 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")'.
+     *
+     * @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 + ")";
+        }
+    }
+}