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33
34 package edu.rice.cs.util;
35
36 import java.security.*;
37
38 /** Not used anymore. <p>
39  * A security manager to prevent exiting the slaveVM indiscriminately. This manager disallows System.exit
40  * (unless you call {@link #exitVM}). It also disallows setting a security manager, since this would override
41  * the exit prevention! If this security manager is enabled and an exit is attempted, either via System.exit
42  * or via {@link #exitVM} when exiting is blocked, a {@link ExitingNotAllowedException} will be thrown.
43  *
44  * @version $Id: PreventExitSecurityManager.java 3901 2006-06-30 05:28:11Z rcartwright $
45  */
46 public class PreventExitSecurityManager extends SecurityManager JavaDoc {
47   
48   private static final Permission SET_MANAGER_PERM = new RuntimePermission JavaDoc("setSecurityManager");
49
50   private final SecurityManager JavaDoc _parent;
51
52   /** Has an unauthorized exit been attempted? */
53   private boolean _exitAttempted = false;
54
55   /** Is it time to exit, for real? */
56   private boolean _timeToExit = false;
57
58   /** Are we in exit blocking mode? */
59   private boolean _blockExit = false;
60
61   /** Is it time to unset this security manager? */
62   private boolean _timeToDeactivate = false;
63
64   /** Creates a PreventExitSecurityManager, delegating all permission checks except for exiting to the given parent
65    * manager.
66    * @param parent SecurityManager to delegate permission to. This may be null, signifying to allow all.
67    */
68   private PreventExitSecurityManager(final SecurityManager JavaDoc parent) { _parent = parent; }
69
70   /** Creates a new exit-preventing security manager, using the previous security manager to delegate to.
71    */
72   public static PreventExitSecurityManager activate() {
73     SecurityManager JavaDoc currentMgr = System.getSecurityManager();
74     if (currentMgr instanceof PreventExitSecurityManager) return (PreventExitSecurityManager) currentMgr;
75     
76     PreventExitSecurityManager mgr = new PreventExitSecurityManager(System.getSecurityManager());
77     System.setSecurityManager(mgr);
78     return mgr;
79   }
80
81   /** Removes this security manager. */
82   public void deactivate() {
83     _timeToDeactivate = true;
84     System.setSecurityManager(_parent);
85   }
86
87   /** Exits the VM unless exiting is presently blocked. Blocking exit is used in test cases that want to see if we
88    * try to exit.
89    */
90   public void exitVM(int status) {
91 // Utilities.showDebug("exitVm(" + status + ") called");
92 if (! _blockExit) _timeToExit = true;
93     System.exit(status);
94   }
95
96   /** Sets whether exiting the VM is unconditionally blocked or not. It's useful to block exiting to allow test cases
97    * to pretend to exit, just to make sure it would have exited under certain conditions.
98    * @param b If true, exiting will never be allowed until set false.
99    */
100   public void setBlockExit(boolean b) { _blockExit = b; }
101
102   /** Returns whether a System.exit was attempted since the last time this method was called. */
103   public boolean exitAttempted() {
104     boolean old = _exitAttempted;
105     _exitAttempted = false;
106     return old;
107   }
108
109   /** Disallow setting security manager, but otherwise delegate to parent. */
110   public void checkPermission(Permission perm) {
111     if (perm.equals(SET_MANAGER_PERM)) {
112       if (! _timeToDeactivate) throw new SecurityException JavaDoc("Can not reset security manager!");
113     }
114     else {
115       if (_parent != null) _parent.checkPermission(perm);
116     }
117   }
118
119   public void checkExit(int status) {
120     if (! _timeToExit) {
121       _exitAttempted = true;
122       throw new ExitingNotAllowedException();
123     }
124   }
125 }
126
127
128
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