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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 gnu.java.lang.CPStringBuilder; 41: 42: import java.io.Serializable; 43: 44: /** 45: * This class is the abstract superclass of all classes that implement 46: * the concept of a permission. A permission consists of a permission name 47: * and optionally a list of actions that relate to the permission. The 48: * actual meaning of the name of the permission is defined only in the 49: * context of a subclass. It may name a resource to which access permissions 50: * are granted (for example, the name of a file) or it might represent 51: * something else entirely. Similarly, the action list only has meaning 52: * within the context of a subclass. Some permission names may have no 53: * actions associated with them. That is, you either have the permission 54: * or you don't. 55: * 56: * <p>The most important method in this class is <code>implies</code>. This 57: * checks whether if one has this permission, then the specified 58: * permission is also implied. As a conceptual example, consider the 59: * permissions "Read All Files" and "Read File foo". The permission 60: * "Read All Files" implies that the caller has permission to read the 61: * file foo. 62: * 63: * <p><code>Permission</code>'s must be immutable - do not change their 64: * state after creation. 65: * 66: * @author Aaron M. Renn (arenn@urbanophile.com) 67: * @see Permissions 68: * @see PermissionCollection 69: * @since 1.1 70: * @status updated to 1.4 71: */ 72: public abstract class Permission implements Guard, Serializable 73: { 74: /** 75: * Compatible with JDK 1.1+. 76: */ 77: private static final long serialVersionUID = -5636570222231596674L; 78: 79: /** 80: * This is the name assigned to this permission object. 81: * 82: * @serial the name of the permission 83: */ 84: private String name; 85: 86: /** 87: * Create an instance with the specified name. 88: * 89: * @param name the permission name 90: */ 91: public Permission(String name) 92: { 93: this.name = name; 94: } 95: 96: /** 97: * This method implements the <code>Guard</code> interface for this class. 98: * It calls the <code>checkPermission</code> method in 99: * <code>SecurityManager</code> with this <code>Permission</code> as its 100: * argument. This method returns silently if the security check succeeds 101: * or throws an exception if it fails. 102: * 103: * @param obj the <code>Object</code> being guarded - ignored by this class 104: * @throws SecurityException if the security check fails 105: * @see GuardedObject 106: * @see SecurityManager#checkPermission(Permission) 107: */ 108: public void checkGuard(Object obj) 109: { 110: SecurityManager sm = System.getSecurityManager(); 111: if (sm != null) 112: sm.checkPermission(this); 113: } 114: 115: /** 116: * This method tests whether this <code>Permission</code> implies that the 117: * specified <code>Permission</code> is also granted. 118: * 119: * @param perm the <code>Permission</code> to test against 120: * @return true if perm is implied by this 121: */ 122: public abstract boolean implies(Permission perm); 123: 124: /** 125: * Check to see if this object equals obj. Use <code>implies</code>, rather 126: * than <code>equals</code>, when making access control decisions. 127: * 128: * @param obj the object to compare to 129: */ 130: public abstract boolean equals(Object obj); 131: 132: /** 133: * This method returns a hash code for this <code>Permission</code>. It 134: * must satisfy the contract of <code>Object.hashCode</code>: it must be 135: * the same for all objects that equals considers to be the same. 136: * 137: * @return a hash value 138: */ 139: public abstract int hashCode(); 140: 141: /** 142: * Get the name of this <code>Permission</code>. 143: * 144: * @return the name 145: */ 146: public final String getName() 147: { 148: return name; 149: } 150: 151: /** 152: * This method returns the list of actions for this <code>Permission</code> 153: * as a <code>String</code>. The string should be in canonical order, for 154: * example, both <code>new FilePermission(f, "write,read")</code> and 155: * <code>new FilePermission(f, "read,write")</code> have the action list 156: * "read,write". 157: * 158: * @return the action list for this <code>Permission</code> 159: */ 160: public abstract String getActions(); 161: 162: /** 163: * This method returns an empty <code>PermissionCollection</code> object 164: * that can store permissions of this type, or <code>null</code> if no 165: * such collection is defined. Subclasses must override this to provide 166: * an appropriate collection when one is needed to accurately calculate 167: * <code>implies</code>. 168: * 169: * @return a new <code>PermissionCollection</code> 170: */ 171: public PermissionCollection newPermissionCollection() 172: { 173: return null; 174: } 175: 176: /** 177: * This method returns a <code>String</code> representation of this 178: * <code>Permission</code> object. This is in the format: 179: * <code>'(' + getClass().getName() + ' ' + getName() + ' ' + getActions 180: * + ')'</code>. 181: * 182: * @return this object as a <code>String</code> 183: */ 184: public String toString() 185: { 186: CPStringBuilder string = new CPStringBuilder(); 187: 188: string = string.append('('); 189: string = string.append(getClass().getName()); 190: string = string.append(' '); 191: string = string.append(getName()); 192: 193: if (!(getActions().equals(""))) 194: { 195: string = string.append(' '); 196: string = string.append(getActions()); 197: } 198: 199: string = string.append(')'); 200: return string.toString(); 201: } 202: } // class Permission