public final class

FilePermission

extends Permission
implements Serializable
java.lang.Object
   ↳ java.security.Permission
     ↳ java.io.FilePermission

Class Overview

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:

read
read permission
write
write permission
execute
execute permission. Allows Runtime.exec to be called. Corresponds to SecurityManager.checkExec.
delete
delete permission. Allows File.delete to be called. Corresponds to SecurityManager.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.

See Also

Summary

Public Constructors
FilePermission(String path, String actions)
Creates a new FilePermission object with the specified actions.
Public Methods
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.
[Expand]
Inherited Methods
From class java.security.Permission
From class java.lang.Object
From interface java.security.Guard

Public Constructors

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 all the files and directories contained in that directory. A pathname that ends with "/-" indicates (recursively) all files and subdirectories contained in that directory. The special pathname "<<ALL FILES>>" matches any file.

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.

A pathname containing an empty string represents an empty path.

Parameters
path the pathname of the file/directory.
actions the action string.
Throws
IllegalArgumentException If actions is null, empty or contains an action other than the specified possible actions.

Public Methods

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.

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, false otherwise.

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".

Returns
  • the canonical string representation of the actions.

public int hashCode ()

Returns the hash code value for this object.

Returns
  • a hash code value for this object.

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 all files in the "/tmp" directory, including the one named "foo".

Parameters
p the permission to check against.
Returns
  • true if the specified permission is not null and is implied by this object, false otherwise.

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.

Returns
  • a new PermissionCollection object suitable for storing FilePermissions.