The AccessController class is used for access control operations
 and decisions.
 
 More specifically, the AccessController class is used for
 three purposes:
 
- to decide whether an access to a critical system resource is to be allowed or denied, based on the security policy currently in effect,
- to mark code as being "privileged", thus affecting subsequent access determinations, and
- to obtain a "snapshot" of the current calling context so access-control decisions from a different context can be made with respect to the saved context.
 The checkPermission method
 determines whether the access request indicated by a specified
 permission should be granted or denied. A sample call appears
 below. In this example, checkPermission will determine
 whether or not to grant "read" access to the file named "testFile" in
 the "/temp" directory.
 
 FilePermission perm = new FilePermission("/temp/testFile", "read");
 AccessController.checkPermission(perm);
 
  If a requested access is allowed,
 checkPermission returns quietly. If denied, an
 AccessControlException is
 thrown. AccessControlException can also be thrown if the requested
 permission is of an incorrect type or contains an invalid value.
 Such information is given whenever possible.
 Suppose the current thread traversed m callers, in the order of caller 1
 to caller 2 to caller m. Then caller m invoked the
 checkPermission method.
 The checkPermission method determines whether access
 is granted or denied based on the following algorithm:
  
 
 for (int i = m; i > 0; i--) {
     if (caller i's domain does not have the permission)
         throw AccessControlException
     else if (caller i is marked as privileged) {
         if (a context was specified in the call to doPrivileged)
             context.checkPermission(permission)
         if (limited permissions were specified in the call to doPrivileged) {
             for (each limited permission) {
                 if (the limited permission implies the requested permission)
                     return;
             }
         } else
             return;
     }
 }
 // Next, check the context inherited when the thread was created.
 // Whenever a new thread is created, the AccessControlContext at
 // that time is stored and associated with the new thread, as the
 // "inherited" context.
 inheritedContext.checkPermission(permission);
 
  A caller can be marked as being "privileged"
 (see doPrivileged and below).
 When making access control decisions, the checkPermission
 method stops checking if it reaches a caller that
 was marked as "privileged" via a doPrivileged
 call without a context argument (see below for information about a
 context argument). If that caller's domain has the
 specified permission and at least one limiting permission argument (if any)
 implies the requested permission, no further checking is done and
 checkPermission
 returns quietly, indicating that the requested access is allowed.
 If that domain does not have the specified permission, an exception
 is thrown, as usual. If the caller's domain had the specified permission
 but it was not implied by any limiting permission arguments given in the call
 to doPrivileged then the permission checking continues
 until there are no more callers or another doPrivileged
 call matches the requested permission and returns normally.
 
The normal use of the "privileged" feature is as follows. If you don't need to return a value from within the "privileged" block, do the following:
 
 somemethod() {
     ...normal code here...
     AccessController.doPrivileged(new PrivilegedAction<Void>() {
         public Void run() {
             // privileged code goes here, for example:
             System.loadLibrary("awt");
             return null; // nothing to return
         }
     });
     ...normal code here...
 }
 
 PrivilegedAction is an interface with a single method, named
 run.
 The above example shows creation of an implementation
 of that interface; a concrete implementation of the
 run method is supplied.
 When the call to doPrivileged is made, an
 instance of the PrivilegedAction implementation is passed
 to it. The doPrivileged method calls the
 run method from the PrivilegedAction
 implementation after enabling privileges, and returns the
 run method's return value as the
 doPrivileged return value (which is
 ignored in this example).
 
If you need to return a value, you can do something like the following:
 
 somemethod() {
     ...normal code here...
     String user = AccessController.doPrivileged(
         new PrivilegedAction<String>() {
         public String run() {
             return System.getProperty("user.name");
             }
         });
     ...normal code here...
 }
 If the action performed in your run method could
 throw a "checked" exception (those listed in the throws clause
 of a method), then you need to use the
 PrivilegedExceptionAction interface instead of the
 PrivilegedAction interface:
  
 
 somemethod() throws FileNotFoundException {
     ...normal code here...
     try {
         FileInputStream fis = AccessController.doPrivileged(
         new PrivilegedExceptionAction<FileInputStream>() {
             public FileInputStream run() throws FileNotFoundException {
                 return new FileInputStream("someFile");
             }
         });
     } catch (PrivilegedActionException e) {
         // e.getException() should be an instance of FileNotFoundException,
         // as only "checked" exceptions will be "wrapped" in a
         // PrivilegedActionException.
         throw (FileNotFoundException) e.getException();
     }
     ...normal code here...
  }
  Be *very* careful in your use of the "privileged" construct, and
 always remember to make the privileged code section as small as possible.
 You can pass Permission arguments to further limit the
 scope of the "privilege" (see below).
 
 Note that checkPermission always performs security checks
 within the context of the currently executing thread.
 Sometimes a security check that should be made within a given context
 will actually need to be done from within a
 different context (for example, from within a worker thread).
 The getContext method and
 AccessControlContext class are provided
 for this situation. The getContext method takes a "snapshot"
 of the current calling context, and places
 it in an AccessControlContext object, which it returns. A sample call is
 the following:
 
AccessControlContext acc = AccessController.getContext()
 AccessControlContext itself has a checkPermission method
 that makes access decisions based on the context it encapsulates,
 rather than that of the current execution thread.
 Code within a different context can thus call that method on the
 previously-saved AccessControlContext object. A sample call is the
 following:
 
acc.checkPermission(permission)
 There are also times where you don't know a priori which permissions
 to check the context against. In these cases you can use the
 doPrivileged method that takes a context. You can also limit the
 scope of the privileged code by passing additional Permission
 parameters.
  
 
 somemethod() {
     AccessController.doPrivileged(new PrivilegedAction<Object>() {
         public Object run() {
             // Code goes here. Any permission checks within this
             // run method will require that the intersection of the
             // caller's protection domain and the snapshot's
             // context have the desired permission. If a requested
             // permission is not implied by the limiting FilePermission
             // argument then checking of the thread continues beyond the
             // caller of doPrivileged.
         }
     }, acc, new FilePermission("/temp/*", read));
     ...normal code here...
 }
  Passing a limiting Permission argument of an instance of
 AllPermission is equivalent to calling the equivalent
 doPrivileged method without limiting Permission
 arguments. Passing a zero length array of Permission disables
 the code privileges so that checking always continues beyond the caller of
 that doPrivileged method.
- Since:
- 1.2
- See Also:
- 
Method SummaryModifier and TypeMethodDescriptionstatic voidcheckPermission(Permission perm) Deprecated, for removal: This API element is subject to removal in a future version.Determines whether the access request indicated by the specified permission should be allowed or denied, based on the currentAccessControlContextand security policy.static <T> TdoPrivileged(PrivilegedAction<T> action) Deprecated, for removal: This API element is subject to removal in a future version.Performs the specifiedPrivilegedActionwith privileges enabled.static <T> TdoPrivileged(PrivilegedAction<T> action, AccessControlContext context) Deprecated, for removal: This API element is subject to removal in a future version.Performs the specifiedPrivilegedActionwith privileges enabled and restricted by the specifiedAccessControlContext.static <T> TdoPrivileged(PrivilegedAction<T> action, AccessControlContext context, Permission... perms) Deprecated, for removal: This API element is subject to removal in a future version.Performs the specifiedPrivilegedActionwith privileges enabled and restricted by the specifiedAccessControlContextand with a privilege scope limited by specifiedPermissionarguments.static <T> TdoPrivileged(PrivilegedExceptionAction<T> action) Deprecated, for removal: This API element is subject to removal in a future version.Performs the specifiedPrivilegedExceptionActionwith privileges enabled.static <T> TdoPrivileged(PrivilegedExceptionAction<T> action, AccessControlContext context) Deprecated, for removal: This API element is subject to removal in a future version.Performs the specifiedPrivilegedExceptionActionwith privileges enabled and restricted by the specifiedAccessControlContext.static <T> TdoPrivileged(PrivilegedExceptionAction<T> action, AccessControlContext context, Permission... perms) Deprecated, for removal: This API element is subject to removal in a future version.Performs the specifiedPrivilegedExceptionActionwith privileges enabled and restricted by the specifiedAccessControlContextand with a privilege scope limited by specifiedPermissionarguments.static <T> TdoPrivilegedWithCombiner(PrivilegedAction<T> action) Deprecated, for removal: This API element is subject to removal in a future version.Performs the specifiedPrivilegedActionwith privileges enabled.static <T> TdoPrivilegedWithCombiner(PrivilegedAction<T> action, AccessControlContext context, Permission... perms) Deprecated, for removal: This API element is subject to removal in a future version.Performs the specifiedPrivilegedActionwith privileges enabled and restricted by the specifiedAccessControlContextand with a privilege scope limited by specifiedPermissionarguments.static <T> TDeprecated, for removal: This API element is subject to removal in a future version.Performs the specifiedPrivilegedExceptionActionwith privileges enabled.static <T> TdoPrivilegedWithCombiner(PrivilegedExceptionAction<T> action, AccessControlContext context, Permission... perms) Deprecated, for removal: This API element is subject to removal in a future version.Performs the specifiedPrivilegedExceptionActionwith privileges enabled and restricted by the specifiedAccessControlContextand with a privilege scope limited by specifiedPermissionarguments.static AccessControlContextDeprecated, for removal: This API element is subject to removal in a future version.This method takes a "snapshot" of the current calling context, which includes the current thread's inheritedAccessControlContextand any limited privilege scope, and places it in anAccessControlContextobject.
- 
Method Details- 
doPrivilegedDeprecated, for removal: This API element is subject to removal in a future version.Performs the specifiedPrivilegedActionwith privileges enabled. The action is performed with all of the permissions possessed by the caller's protection domain.If the action's runmethod throws an (unchecked) exception, it will propagate through this method.Note that any DomainCombinerassociated with the currentAccessControlContextwill be ignored while the action is performed.- Type Parameters:
- T- the type of the value returned by the PrivilegedAction's- runmethod.
- Parameters:
- action- the action to be performed.
- Returns:
- the value returned by the action's runmethod.
- Throws:
- NullPointerException- if the action is- null
- See Also:
 
- 
doPrivilegedWithCombinerDeprecated, for removal: This API element is subject to removal in a future version.Performs the specifiedPrivilegedActionwith privileges enabled. The action is performed with all of the permissions possessed by the caller's protection domain.If the action's runmethod throws an (unchecked) exception, it will propagate through this method.This method preserves the current AccessControlContext's DomainCombiner(which may be null) while the action is performed.- Type Parameters:
- T- the type of the value returned by the PrivilegedAction's- runmethod.
- Parameters:
- action- the action to be performed.
- Returns:
- the value returned by the action's runmethod.
- Throws:
- NullPointerException- if the action is- null
- Since:
- 1.6
- See Also:
 
- 
doPrivilegedDeprecated, for removal: This API element is subject to removal in a future version.Performs the specifiedPrivilegedActionwith privileges enabled and restricted by the specifiedAccessControlContext. The action is performed with the intersection of the permissions possessed by the caller's protection domain, and those possessed by the domains represented by the specifiedAccessControlContext.If the action's runmethod throws an (unchecked) exception, it will propagate through this method.If a security manager is installed and the specified AccessControlContextwas not created by system code and the caller'sProtectionDomainhas not been granted the "createAccessControlContext"SecurityPermission, then the action is performed with no permissions.- Type Parameters:
- T- the type of the value returned by the PrivilegedAction's- runmethod.
- Parameters:
- action- the action to be performed.
- context- an access control context representing the restriction to be applied to the caller's domain's privileges before performing the specified action. If the context is- null, then no additional restriction is applied.
- Returns:
- the value returned by the action's runmethod.
- Throws:
- NullPointerException- if the action is- null
- See Also:
 
- 
doPrivilegedpublic static <T> T doPrivileged(PrivilegedAction<T> action, AccessControlContext context, Permission... perms) Deprecated, for removal: This API element is subject to removal in a future version.Performs the specifiedPrivilegedActionwith privileges enabled and restricted by the specifiedAccessControlContextand with a privilege scope limited by specifiedPermissionarguments. The action is performed with the intersection of the permissions possessed by the caller's protection domain, and those possessed by the domains represented by the specifiedAccessControlContext.If the action's runmethod throws an (unchecked) exception, it will propagate through this method.If a security manager is installed and the specified AccessControlContextwas not created by system code and the caller'sProtectionDomainhas not been granted the "createAccessControlContext"SecurityPermission, then the action is performed with no permissions.- Type Parameters:
- T- the type of the value returned by the PrivilegedAction's- runmethod.
- Parameters:
- action- the action to be performed.
- context- an access control context representing the restriction to be applied to the caller's domain's privileges before performing the specified action. If the context is- null, then no additional restriction is applied.
- perms- the- Permissionarguments which limit the scope of the caller's privileges. The number of arguments is variable.
- Returns:
- the value returned by the action's runmethod.
- Throws:
- NullPointerException- if action or perms or any element of perms is- null
- Since:
- 1.8
- See Also:
 
- 
doPrivilegedWithCombinerpublic static <T> T doPrivilegedWithCombiner(PrivilegedAction<T> action, AccessControlContext context, Permission... perms) Deprecated, for removal: This API element is subject to removal in a future version.Performs the specifiedPrivilegedActionwith privileges enabled and restricted by the specifiedAccessControlContextand with a privilege scope limited by specifiedPermissionarguments. The action is performed with the intersection of the permissions possessed by the caller's protection domain, and those possessed by the domains represented by the specifiedAccessControlContext.If the action's runmethod throws an (unchecked) exception, it will propagate through this method.This method preserves the current AccessControlContext's DomainCombiner(which may be null) while the action is performed.If a security manager is installed and the specified AccessControlContextwas not created by system code and the caller'sProtectionDomainhas not been granted the "createAccessControlContext"SecurityPermission, then the action is performed with no permissions.- Type Parameters:
- T- the type of the value returned by the PrivilegedAction's- runmethod.
- Parameters:
- action- the action to be performed.
- context- an access control context representing the restriction to be applied to the caller's domain's privileges before performing the specified action. If the context is- null, then no additional restriction is applied.
- perms- the- Permissionarguments which limit the scope of the caller's privileges. The number of arguments is variable.
- Returns:
- the value returned by the action's runmethod.
- Throws:
- NullPointerException- if action or perms or any element of perms is- null
- Since:
- 1.8
- See Also:
 
- 
doPrivilegedpublic static <T> T doPrivileged(PrivilegedExceptionAction<T> action) throws PrivilegedActionException Deprecated, for removal: This API element is subject to removal in a future version.Performs the specifiedPrivilegedExceptionActionwith privileges enabled. The action is performed with all of the permissions possessed by the caller's protection domain.If the action's runmethod throws an unchecked exception, it will propagate through this method.Note that any DomainCombinerassociated with the currentAccessControlContextwill be ignored while the action is performed.- Type Parameters:
- T- the type of the value returned by the PrivilegedExceptionAction's- runmethod.
- Parameters:
- action- the action to be performed
- Returns:
- the value returned by the action's runmethod
- Throws:
- PrivilegedActionException- if the specified action's- runmethod threw a checked exception
- NullPointerException- if the action is- null
- See Also:
 
- 
doPrivilegedWithCombinerpublic static <T> T doPrivilegedWithCombiner(PrivilegedExceptionAction<T> action) throws PrivilegedActionException Deprecated, for removal: This API element is subject to removal in a future version.Performs the specifiedPrivilegedExceptionActionwith privileges enabled. The action is performed with all of the permissions possessed by the caller's protection domain.If the action's runmethod throws an unchecked exception, it will propagate through this method.This method preserves the current AccessControlContext's DomainCombiner(which may be null) while the action is performed.- Type Parameters:
- T- the type of the value returned by the PrivilegedExceptionAction's- runmethod.
- Parameters:
- action- the action to be performed.
- Returns:
- the value returned by the action's runmethod
- Throws:
- PrivilegedActionException- if the specified action's- runmethod threw a checked exception
- NullPointerException- if the action is- null
- Since:
- 1.6
- See Also:
 
- 
doPrivilegedpublic static <T> T doPrivileged(PrivilegedExceptionAction<T> action, AccessControlContext context) throws PrivilegedActionException Deprecated, for removal: This API element is subject to removal in a future version.Performs the specifiedPrivilegedExceptionActionwith privileges enabled and restricted by the specifiedAccessControlContext. The action is performed with the intersection of the permissions possessed by the caller's protection domain, and those possessed by the domains represented by the specifiedAccessControlContext.If the action's runmethod throws an unchecked exception, it will propagate through this method.If a security manager is installed and the specified AccessControlContextwas not created by system code and the caller'sProtectionDomainhas not been granted the "createAccessControlContext"SecurityPermission, then the action is performed with no permissions.- Type Parameters:
- T- the type of the value returned by the PrivilegedExceptionAction's- runmethod.
- Parameters:
- action- the action to be performed
- context- an access control context representing the restriction to be applied to the caller's domain's privileges before performing the specified action. If the context is- null, then no additional restriction is applied.
- Returns:
- the value returned by the action's runmethod
- Throws:
- PrivilegedActionException- if the specified action's- runmethod threw a checked exception
- NullPointerException- if the action is- null
- See Also:
 
- 
doPrivilegedpublic static <T> T doPrivileged(PrivilegedExceptionAction<T> action, AccessControlContext context, Permission... perms) throws PrivilegedActionException Deprecated, for removal: This API element is subject to removal in a future version.Performs the specifiedPrivilegedExceptionActionwith privileges enabled and restricted by the specifiedAccessControlContextand with a privilege scope limited by specifiedPermissionarguments. The action is performed with the intersection of the permissions possessed by the caller's protection domain, and those possessed by the domains represented by the specifiedAccessControlContext.If the action's runmethod throws an (unchecked) exception, it will propagate through this method.If a security manager is installed and the specified AccessControlContextwas not created by system code and the caller'sProtectionDomainhas not been granted the "createAccessControlContext"SecurityPermission, then the action is performed with no permissions.- Type Parameters:
- T- the type of the value returned by the PrivilegedExceptionAction's- runmethod.
- Parameters:
- action- the action to be performed.
- context- an access control context representing the restriction to be applied to the caller's domain's privileges before performing the specified action. If the context is- null, then no additional restriction is applied.
- perms- the- Permissionarguments which limit the scope of the caller's privileges. The number of arguments is variable.
- Returns:
- the value returned by the action's runmethod.
- Throws:
- PrivilegedActionException- if the specified action's- runmethod threw a checked exception
- NullPointerException- if action or perms or any element of perms is- null
- Since:
- 1.8
- See Also:
 
- 
doPrivilegedWithCombinerpublic static <T> T doPrivilegedWithCombiner(PrivilegedExceptionAction<T> action, AccessControlContext context, Permission... perms) throws PrivilegedActionException Deprecated, for removal: This API element is subject to removal in a future version.Performs the specifiedPrivilegedExceptionActionwith privileges enabled and restricted by the specifiedAccessControlContextand with a privilege scope limited by specifiedPermissionarguments. The action is performed with the intersection of the permissions possessed by the caller's protection domain, and those possessed by the domains represented by the specifiedAccessControlContext.If the action's runmethod throws an (unchecked) exception, it will propagate through this method.This method preserves the current AccessControlContext's DomainCombiner(which may be null) while the action is performed.If a security manager is installed and the specified AccessControlContextwas not created by system code and the caller'sProtectionDomainhas not been granted the "createAccessControlContext"SecurityPermission, then the action is performed with no permissions.- Type Parameters:
- T- the type of the value returned by the PrivilegedExceptionAction's- runmethod.
- Parameters:
- action- the action to be performed.
- context- an access control context representing the restriction to be applied to the caller's domain's privileges before performing the specified action. If the context is- null, then no additional restriction is applied.
- perms- the- Permissionarguments which limit the scope of the caller's privileges. The number of arguments is variable.
- Returns:
- the value returned by the action's runmethod.
- Throws:
- PrivilegedActionException- if the specified action's- runmethod threw a checked exception
- NullPointerException- if action or perms or any element of perms is- null
- Since:
- 1.8
- See Also:
 
- 
getContextDeprecated, for removal: This API element is subject to removal in a future version.This method takes a "snapshot" of the current calling context, which includes the current thread's inheritedAccessControlContextand any limited privilege scope, and places it in anAccessControlContextobject. This context may then be checked at a later point, possibly in another thread.- Returns:
- the AccessControlContextbased on the current context.
- See Also:
 
- 
checkPermissionDeprecated, for removal: This API element is subject to removal in a future version.Determines whether the access request indicated by the specified permission should be allowed or denied, based on the currentAccessControlContextand security policy. This method quietly returns if the access request is permitted, or throws anAccessControlExceptionotherwise. ThegetPermissionmethod of theAccessControlExceptionreturns thePermissionobject instance (perm}.- Parameters:
- perm- the requested permission.
- Throws:
- AccessControlException- if the specified permission is not permitted, based on the current security policy.
- NullPointerException- if the specified permission is- nulland is checked based on the security policy currently in effect.
 
 
-