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java.io
public final class: FilePermission [javadoc | source]
java.lang.Object
   java.security.Permission
      java.io.FilePermission

All Implemented Interfaces:
    Serializable, Guard

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", "delete", and "readlink". 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.
readlink
read link permission. Allows the target of a symbolic link to be read by invoking the readSymbolicLink method.

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.

Constructor:
 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", "delete", and "readlink".

    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.
 FilePermission(String path,
    int mask) 
    Creates a new FilePermission object using an action mask. More efficient than the FilePermission(String, String) constructor. Can be used from within code that needs to create a FilePermission object to pass into the implies method.
    Parameters:
    path - the pathname of the file/directory.
    mask - the action mask to use.
Method from java.io.FilePermission Summary:
equals,   getActions,   getMask,   hashCode,   implies,   impliesIgnoreMask,   newPermissionCollection
Methods from java.security.Permission:
checkGuard,   equals,   getActions,   getName,   hashCode,   implies,   newPermissionCollection,   toString
Methods from java.lang.Object:
clone,   equals,   finalize,   getClass,   hashCode,   notify,   notifyAll,   toString,   wait,   wait,   wait
Method from java.io.FilePermission Detail:
 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.

 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, readlink. For example, if this FilePermission object allows both write and read actions, a call to getActions will return the string "read,write".
 int getMask() 
    Return the current action mask. Used by the FilePermissionCollection.
 public int hashCode() 
    Returns the 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".
 boolean impliesIgnoreMask(FilePermission that) 
    Checks if the Permission's actions are a proper subset of the this object's actions. Returns the effective mask iff the this FilePermission's path also implies that FilePermission's path.
 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.