File read permission in java

File read permission in java

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File read permission in java

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 «<>» 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 «<>» 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 Summary

Method Summary

Methods inherited from class java.security.Permission

Methods inherited from class java.lang.Object

Constructor Detail

FilePermission

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 «>» 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.

Method Detail

implies

• 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».

equals

Checks two FilePermission objects for equality. Checks that obj is a FilePermission, and has the same pathname and actions as this object.

hashCode

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».

newPermissionCollection

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.

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