java.io

Class FilePermission

Implemented Interfaces:
Guard, Serializable

public final class FilePermission
extends Permission
implements Serializable

This class represents access to a file or directory. A FilePermission consists of a pathname and a set of actions valid for that pathname.

Pathname is the pathname of the file or directory granted the specified actions. A pathname that ends in "/*" (where "/" is the file separator character, File.separatorChar) indicates all the files and directories contained in that directory. A pathname that ends with "/-" indicates (recursively) all files and subdirectories contained in that directory. A pathname consisting of the special token "<<ALL FILES>>" matches any file.

Note: A pathname consisting of a single "*" indicates all the files in the current directory, while a pathname consisting of a single "-" indicates all the files in the current directory and (recursively) all files and subdirectories contained in the current directory.

The actions to be granted are passed to the constructor in a string containing a list of one or more comma-separated keywords. The possible keywords are "read", "write", "execute", and "delete". Their meaning is defined as follows:

Runtime.execSecurityManager.checkExec
File.deleteSecurityManager.checkDelete

The actions string is converted to lowercase before processing.

Be careful when granting FilePermissions. Think about the implications of granting read and especially write access to various files and directories. The "<<ALL FILES>>" permission with write action is especially dangerous. This grants permission to write to the entire file system. One thing this effectively allows is replacement of the system binary, including the JVM runtime environment.

Please note: Code can always read a file from the same directory it's in (or a subdirectory of that directory); it does not need explicit permission to do so.

Since:
1.2
See Also:
Permission, Permissions, PermissionCollection, Serialized Form

Constructor Summary

FilePermission(String path, String actions)
Creates a new FilePermission object with the specified actions.

Method Summary

boolean
equals(Object obj)
Checks two FilePermission objects for equality.
String
getActions()
Returns the "canonical string representation" of the actions.
int
hashCode()
Returns the hash code value for this object.
boolean
implies(Permission p)
Checks if this FilePermission object "implies" the specified permission.
PermissionCollection
newPermissionCollection()
Returns a new PermissionCollection object for storing FilePermission objects.

Methods inherited from class java.security.Permission

checkGuard, equals, getActions, getName, hashCode, implies, newPermissionCollection, toString

Methods inherited from class java.lang.Object

clone, equals, extends Object> getClass, finalize, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

FilePermission

public FilePermission(String path,
                      String actions)
Creates a new FilePermission object with the specified actions. path is the pathname of a file or directory, and actions contains a comma-separated list of the desired actions granted on the file or directory. Possible actions are "read", "write", "execute", and "delete".

A pathname that ends in "/*" (where "/" is the file separator character, File.separatorChar) indicates a directory and all the files contained in that directory. A pathname that ends with "/-" indicates a directory and (recursively) all files and subdirectories contained in that directory. The special pathname "<<ALL FILES>>" matches all files.

A pathname consisting of a single "*" indicates all the files in the current directory, while a pathname consisting of a single "-" indicates all the files in the current directory and (recursively) all files and subdirectories contained in the current directory.

Parameters:
path - the pathname of the file/directory.
actions - the action string.
Usages and Demos :

View More Examples of FilePermission(String path,String actions)
   1:     Permission perm1 = new FilePermission( "c:\\windows\\*", "read,write" );
   2:     Permission perm2 = new FilePermission( "c:\\windows\\fonts", "read" );
   3:     
   4:         ...
   5:     
   6:     if ( !perm2.implies( new FilePermission("c:\\windows\\fonts", "write") ) )
   7:       System.out.println( perm1 + " not implies " + perm2 );
   8:   }
   9: }

View Full Code Here
   1:         try {
   2:             collection.add(new FilePermission("file", "read"), false);
   3:             fail();
   4:         }
   5:         catch (IllegalArgumentException e) {

View Full Code Here
   1:         }
   2:         final Permission permission2 = new FilePermission("/toto","delete");
   3:         try{
   4:              Subject.doAsPrivileged(subject, new PrivilegedExceptionAction() {
   5:                  public Object run()  {

View Full Code Here

Method Details

equals

public boolean equals(Object obj)
Checks two FilePermission objects for equality. Checks that obj is a FilePermission, and has the same pathname and actions as this object.

Overrides:
equals in interface Permission
Parameters:
obj - the object we are testing for equality with this object.
Returns:
true if obj is a FilePermission, and has the same pathname and actions as this FilePermission object.

getActions

public String getActions()
Returns the "canonical string representation" of the actions. That is, this method always returns present actions in the following order: read, write, execute, delete. For example, if this FilePermission object allows both write and read actions, a call to getActions will return the string "read,write".
Overrides:
getActions in interface Permission
Returns:
the canonical string representation of the actions.

hashCode

public int hashCode()
Returns the hash code value for this object.
Overrides:
hashCode in interface Permission
Returns:
a hash code value for this object.

implies

public boolean implies(Permission p)
Checks if this FilePermission object "implies" the specified permission.

More specifically, this method returns true if:

  • p is an instanceof FilePermission,

  • p's actions are a proper subset of this object's actions, and

  • p's pathname is implied by this object's pathname. For example, "/tmp/*" implies "/tmp/foo", since "/tmp/*" encompasses the "/tmp" directory and all files in that directory, including the one named "foo".
Overrides:
implies in interface Permission
Parameters:
p - the permission to check against.
Returns:
true if the specified permission is implied by this object, false if not.
Usages and Demos :

View More Examples of implies(Permission p)
   1: 
   2: import java.io.FilePermission;
   3: import java.util.Dictionary;
   4:         ...
   5:     public BundleLocationCondition(Bundle bundle, String location) {
   6:         FilePermission locationPat = new FilePermission(location, "read");
   7:         FilePermission sourcePat = new FilePermission(bundle.getLocation()
   8:         ...
   9:                 .toString(), "read");
  10:         satisfied = locationPat.implies(sourcePat);
  11:     }

View Full Code Here

newPermissionCollection

public PermissionCollection newPermissionCollection()
Returns a new PermissionCollection object for storing FilePermission objects.

FilePermission objects must be stored in a manner that allows them to be inserted into the collection in any order, but that also enables the PermissionCollection implies method to be implemented in an efficient (and consistent) manner.

For example, if you have two FilePermissions:

  1. "/tmp/-", "read"
  2. "/tmp/scratch/foo", "write"

and you are calling the implies method with the FilePermission:

   "/tmp/scratch/foo", "read,write", 
 
then the implies function must take into account both the "/tmp/-" and "/tmp/scratch/foo" permissions, so the effective permission is "read,write", and implies returns true. The "implies" semantics for FilePermissions are handled properly by the PermissionCollection object returned by this newPermissionCollection method.
Overrides:
newPermissionCollection in interface Permission
Returns:
a new PermissionCollection object suitable for storing FilePermissions.