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[/] [scarts/] [trunk/] [toolchain/] [scarts-gcc/] [gcc-4.1.1/] [libjava/] [classpath/] [java/] [security/] [Permission.java] - Blame information for rev 14

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1 14 jlechner 
/* Permission.java -- The superclass for all permission objects
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   Copyright (C) 1998, 2001, 2002, 2005  Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING.  If not, write to the
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library.  Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module.  An independent module is a module which is not derived from
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or based on this library.  If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so.  If you do not wish to do so, delete this
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exception statement from your version. */
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package java.security;
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import java.io.Serializable;
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/**
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 * This class is the abstract superclass of all classes that implement
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 * the concept of a permission.  A permission consists of a permission name
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 * and optionally a list of actions that relate to the permission.  The
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 * actual meaning of the name of the permission is defined only in the
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 * context of a subclass.  It may name a resource to which access permissions
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 * are granted (for example, the name of a file) or it might represent
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 * something else entirely.  Similarly, the action list only has meaning
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 * within the context of a subclass.  Some permission names may have no
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 * actions associated with them.  That is, you either have the permission
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 * or you don't.
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 *
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 * <p>The most important method in this class is <code>implies</code>.  This
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 * checks whether if one has this permission, then the specified
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 * permission is also implied.  As a conceptual example, consider the
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 * permissions "Read All Files" and "Read File foo".  The permission
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 * "Read All Files" implies that the caller has permission to read the
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 * file foo.
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 *
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 * <p><code>Permission</code>'s must be immutable - do not change their
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 * state after creation.
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 *
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 * @author Aaron M. Renn (arenn@urbanophile.com)
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 * @see Permissions
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 * @see PermissionCollection
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 * @since 1.1
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 * @status updated to 1.4
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 */
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public abstract class Permission implements Guard, Serializable
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{
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  /**
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   * Compatible with JDK 1.1+.
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   */
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  private static final long serialVersionUID = -5636570222231596674L;
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  /**
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   * This is the name assigned to this permission object.
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   *
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   * @serial the name of the permission
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   */
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  private String name;
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  /**
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   * Create an instance with the specified name.
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   *
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   * @param name the permission name
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   */
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  public Permission(String name)
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  {
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    this.name = name;
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  }
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  /**
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   * This method implements the <code>Guard</code> interface for this class.
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   * It calls the <code>checkPermission</code> method in
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   * <code>SecurityManager</code> with this <code>Permission</code> as its
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   * argument.  This method returns silently if the security check succeeds
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   * or throws an exception if it fails.
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   *
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   * @param obj the <code>Object</code> being guarded - ignored by this class
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   * @throws SecurityException if the security check fails
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   * @see GuardedObject
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   * @see SecurityManager#checkPermission(Permission)
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   */
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  public void checkGuard(Object obj)
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  {
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    SecurityManager sm = System.getSecurityManager();
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    if (sm != null)
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      sm.checkPermission(this);
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  }
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  /**
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   * This method tests whether this <code>Permission</code> implies that the
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   * specified <code>Permission</code> is also granted.
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   *
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   * @param perm the <code>Permission</code> to test against
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   * @return true if perm is implied by this
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   */
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  public abstract boolean implies(Permission perm);
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  /**
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   * Check to see if this object equals obj. Use <code>implies</code>, rather
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   * than <code>equals</code>, when making access control decisions.
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   *
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   * @param obj the object to compare to
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   */
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  public abstract boolean equals(Object obj);
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  /**
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   * This method returns a hash code for this <code>Permission</code>. It
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   * must satisfy the contract of <code>Object.hashCode</code>: it must be
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   * the same for all objects that equals considers to be the same.
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   *
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   * @return a hash value
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   */
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  public abstract int hashCode();
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  /**
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   * Get the name of this <code>Permission</code>.
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   *
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   * @return the name
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   */
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  public final String getName()
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  {
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    return name;
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  }
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  /**
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   * This method returns the list of actions for this <code>Permission</code>
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   * as a <code>String</code>. The string should be in canonical order, for
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   * example, both <code>new FilePermission(f, "write,read")</code> and
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   * <code>new FilePermission(f, "read,write")</code> have the action list
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   * "read,write".
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   *
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   * @return the action list for this <code>Permission</code>
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   */
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  public abstract String getActions();
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  /**
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   * This method returns an empty <code>PermissionCollection</code> object
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   * that can store permissions of this type, or <code>null</code> if no
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   * such collection is defined. Subclasses must override this to provide
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   * an appropriate collection when one is needed to accurately calculate
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   * <code>implies</code>.
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   *
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   * @return a new <code>PermissionCollection</code>
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   */
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  public PermissionCollection newPermissionCollection()
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  {
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    return null;
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  }
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  /**
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   * This method returns a <code>String</code> representation of this
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   * <code>Permission</code> object. This is in the format:
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   * <code>'(' + getClass().getName() + ' ' + getName() + ' ' + getActions
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   * + ')'</code>.
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   *
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   * @return this object as a <code>String</code>
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   */
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  public String toString()
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  {
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    return '(' + getClass().getName() + ' ' + getName() + ' '
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      + getActions() + ')';
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  }
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} // class Permission

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