Source for java.security.Permission

   1: /* Permission.java -- The superclass for all permission objects
   2:    Copyright (C) 1998, 2001, 2002, 2005  Free Software Foundation, Inc.
   3: 
   4: This file is part of GNU Classpath.
   5: 
   6: GNU Classpath is free software; you can redistribute it and/or modify
   7: it under the terms of the GNU General Public License as published by
   8: the Free Software Foundation; either version 2, or (at your option)
   9: any later version.
  10: 
  11: GNU Classpath is distributed in the hope that it will be useful, but
  12: WITHOUT ANY WARRANTY; without even the implied warranty of
  13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14: General Public License for more details.
  15: 
  16: You should have received a copy of the GNU General Public License
  17: along with GNU Classpath; see the file COPYING.  If not, write to the
  18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 USA.
  20: 
  21: Linking this library statically or dynamically with other modules is
  22: making a combined work based on this library.  Thus, the terms and
  23: conditions of the GNU General Public License cover the whole
  24: combination.
  25: 
  26: As a special exception, the copyright holders of this library give you
  27: permission to link this library with independent modules to produce an
  28: executable, regardless of the license terms of these independent
  29: modules, and to copy and distribute the resulting executable under
  30: terms of your choice, provided that you also meet, for each linked
  31: independent module, the terms and conditions of the license of that
  32: module.  An independent module is a module which is not derived from
  33: or based on this library.  If you modify this library, you may extend
  34: this exception to your version of the library, but you are not
  35: obligated to do so.  If you do not wish to do so, delete this
  36: exception statement from your version. */
  37: 
  38: package java.security;
  39: 
  40: import java.io.Serializable;
  41: 
  42: /**
  43:  * This class is the abstract superclass of all classes that implement
  44:  * the concept of a permission.  A permission consists of a permission name
  45:  * and optionally a list of actions that relate to the permission.  The
  46:  * actual meaning of the name of the permission is defined only in the
  47:  * context of a subclass.  It may name a resource to which access permissions
  48:  * are granted (for example, the name of a file) or it might represent
  49:  * something else entirely.  Similarly, the action list only has meaning
  50:  * within the context of a subclass.  Some permission names may have no
  51:  * actions associated with them.  That is, you either have the permission
  52:  * or you don't.
  53:  *
  54:  * <p>The most important method in this class is <code>implies</code>.  This
  55:  * checks whether if one has this permission, then the specified
  56:  * permission is also implied.  As a conceptual example, consider the
  57:  * permissions "Read All Files" and "Read File foo".  The permission
  58:  * "Read All Files" implies that the caller has permission to read the
  59:  * file foo.
  60:  *
  61:  * <p><code>Permission</code>'s must be immutable - do not change their
  62:  * state after creation.
  63:  *
  64:  * @author Aaron M. Renn (arenn@urbanophile.com)
  65:  * @see Permissions
  66:  * @see PermissionCollection
  67:  * @since 1.1
  68:  * @status updated to 1.4
  69:  */
  70: public abstract class Permission implements Guard, Serializable
  71: {
  72:   /**
  73:    * Compatible with JDK 1.1+.
  74:    */
  75:   private static final long serialVersionUID = -5636570222231596674L;
  76: 
  77:   /**
  78:    * This is the name assigned to this permission object.
  79:    *
  80:    * @serial the name of the permission
  81:    */
  82:   private String name;
  83: 
  84:   /**
  85:    * Create an instance with the specified name.
  86:    *
  87:    * @param name the permission name
  88:    */
  89:   public Permission(String name)
  90:   {
  91:     this.name = name;
  92:   }
  93: 
  94:   /**
  95:    * This method implements the <code>Guard</code> interface for this class.
  96:    * It calls the <code>checkPermission</code> method in
  97:    * <code>SecurityManager</code> with this <code>Permission</code> as its
  98:    * argument.  This method returns silently if the security check succeeds
  99:    * or throws an exception if it fails.
 100:    *
 101:    * @param obj the <code>Object</code> being guarded - ignored by this class
 102:    * @throws SecurityException if the security check fails
 103:    * @see GuardedObject
 104:    * @see SecurityManager#checkPermission(Permission)
 105:    */
 106:   public void checkGuard(Object obj)
 107:   {
 108:     SecurityManager sm = System.getSecurityManager();
 109:     if (sm != null)
 110:       sm.checkPermission(this);
 111:   }
 112: 
 113:   /**
 114:    * This method tests whether this <code>Permission</code> implies that the
 115:    * specified <code>Permission</code> is also granted.
 116:    *
 117:    * @param perm the <code>Permission</code> to test against
 118:    * @return true if perm is implied by this
 119:    */
 120:   public abstract boolean implies(Permission perm);
 121: 
 122:   /**
 123:    * Check to see if this object equals obj. Use <code>implies</code>, rather
 124:    * than <code>equals</code>, when making access control decisions.
 125:    *
 126:    * @param obj the object to compare to
 127:    */
 128:   public abstract boolean equals(Object obj);
 129: 
 130:   /**
 131:    * This method returns a hash code for this <code>Permission</code>. It
 132:    * must satisfy the contract of <code>Object.hashCode</code>: it must be
 133:    * the same for all objects that equals considers to be the same.
 134:    *
 135:    * @return a hash value
 136:    */
 137:   public abstract int hashCode();
 138: 
 139:   /**
 140:    * Get the name of this <code>Permission</code>.
 141:    *
 142:    * @return the name
 143:    */
 144:   public final String getName()
 145:   {
 146:     return name;
 147:   }
 148: 
 149:   /**
 150:    * This method returns the list of actions for this <code>Permission</code>
 151:    * as a <code>String</code>. The string should be in canonical order, for
 152:    * example, both <code>new FilePermission(f, "write,read")</code> and
 153:    * <code>new FilePermission(f, "read,write")</code> have the action list
 154:    * "read,write".
 155:    *
 156:    * @return the action list for this <code>Permission</code>
 157:    */
 158:   public abstract String getActions();
 159: 
 160:   /**
 161:    * This method returns an empty <code>PermissionCollection</code> object
 162:    * that can store permissions of this type, or <code>null</code> if no
 163:    * such collection is defined. Subclasses must override this to provide
 164:    * an appropriate collection when one is needed to accurately calculate
 165:    * <code>implies</code>.
 166:    *
 167:    * @return a new <code>PermissionCollection</code>
 168:    */
 169:   public PermissionCollection newPermissionCollection()
 170:   {
 171:     return null;
 172:   }
 173: 
 174:   /**
 175:    * This method returns a <code>String</code> representation of this
 176:    * <code>Permission</code> object. This is in the format:
 177:    * <code>'(' + getClass().getName() + ' ' + getName() + ' ' + getActions
 178:    * + ')'</code>.
 179:    *
 180:    * @return this object as a <code>String</code>
 181:    */
 182:   public String toString()
 183:   {
 184:     StringBuffer string = new StringBuffer(); 
 185:     
 186:     string = string.append('(');
 187:     string = string.append(getClass().getName());
 188:     string = string.append(' ');
 189:     string = string.append(getName());
 190:     
 191:     if (!(getActions().equals("")))
 192:       {
 193:         string = string.append(' ');
 194:         string = string.append(getActions());
 195:       }
 196:    
 197:     string = string.append(')');
 198:     return string.toString();     
 199:   }
 200: } // class Permission