Interface StorageFile

All Known Implementing Classes:
CPFile, DirFile, InputStreamFile, JarDBFile, URLFile, VirtualFile

public interface StorageFile
This interface abstracts file naming. Any method in this interface that also appears in the java.io.File class should behave as the java.io.File method does.

When used by the database engine all files will be under either the database directory, specified by the databaseName argument of the StorageFactory.init method, or under the temporary file directory returned by the StorageFactory.getTempDir method. All relative path names are relative to the database directory.

The database engine will call this interface's methods from its own privilege blocks.

Different threads may operate on the same underlying file at the same time, either through the same or different StorageFile objects. The StiFile implementation must be capable of handling this.

See Also:
  • Field Details

  • Method Details

    • list

      String[] list()
      Get the names of all files and sub-directories in the directory named by this path name. This method is only used in a writable database.
      Returns:
      An array of the names of the files and directories in this directory denoted by this abstract pathname. The returned array will have length 0 if this directory is empty. Returns null if this StorageFile is not a directory, or if an I/O error occurs. The return value is undefined if the database is read-only.
    • canWrite

      boolean canWrite()
      Determine whether the named file is writable.
      Returns:
      true if the file exists and is writable, false if not.
    • exists

      boolean exists()
      Tests whether the named file exists.
      Returns:
      true if the named file exists, false if not.
    • isDirectory

      boolean isDirectory()
      Tests whether the named file is a directory, or not. This is only called in writable storage factories.
      Returns:
      true if named file exists and is a directory, false if not. The return value is undefined if the storage is read-only.
    • delete

      boolean delete()
      Deletes the named file or empty directory. This method does not delete non-empty directories.
      Returns:
      true if the named file or directory is successfully deleted, false if not
    • deleteAll

      boolean deleteAll()
      Deletes the named file and, if it is a directory, all the files and directories it contains.
      Returns:
      true if the named file or directory is successfully deleted, false if not
    • getPath

      String getPath()
      Converts this StorageFile into a pathname string. The character returned by StorageFactory.getSeparator() is used to separate the directory and file names in the sequence.

      The returned path may include the database directory. Therefore it cannot be directly used to make an StorageFile equivalent to this one.

      Returns:
      The pathname as a string.
      See Also:
    • getCanonicalPath

      String getCanonicalPath() throws IOException
      Converts this StorageFile into a canonical pathname string. The form of the canonical path is system dependent.
      Returns:
      The pathname as a string.
      Throws:
      IOException - if an I/O error occurred while finding the canonical name
    • getName

      String getName()
      Returns:
      The last segment in the path name, "" if the path name sequence is empty.
    • createNewFile

      boolean createNewFile() throws IOException
      If the named file does not already exist then create it as an empty normal file. The implementation must synchronize with other threads accessing the same file (in the same or a different process). If two threads both attempt to create a file with the same name at the same time then at most one should succeed.
      Returns:
      true if this thread's invocation of createNewFile successfully created the named file; false if not, i.e. false if the named file already exists or if another concurrent thread created it.
      Throws:
      IOException - - If the directory does not exist or some other I/O error occurred
    • renameTo

      boolean renameTo(StorageFile newName)
      Rename the file denoted by this name. Note that StorageFile objects are immutable. This method renames the underlying file, it does not change this StorageFile object. The StorageFile object denotes the same name as before, however the exists() method will return false after the renameTo method executes successfully.

      It is not specified whether this method will succeed if a file already exists under the new name.

      Parameters:
      newName - the new name.
      Returns:
      true if the rename succeeded, false if not.
    • mkdir

      boolean mkdir()
      Creates the named directory.
      Returns:
      true if the directory was created; false if not.
    • mkdirs

      boolean mkdirs()
      Creates the named directory, and all nonexistent parent directories.
      Returns:
      true if the directory was created, false if not
    • getParentDir

      StorageFile getParentDir()
      Get the name of the parent directory if this name includes a parent.
      Returns:
      An StorageFile denoting the parent directory of this StorageFile, if it has a parent, null if it does not have a parent.
    • setReadOnly

      boolean setReadOnly()
      Make the named file or directory read-only. This interface does not specify whether this also makes the file undeletable.
      Returns:
      true if the named file or directory was made read-only, or it already was read-only; false if not.
    • getOutputStream

      OutputStream getOutputStream() throws FileNotFoundException
      Creates an output stream from a file name. If a normal file already exists with this name it will first be truncated to zero length.
      Returns:
      an output stream suitable for writing to the file.
      Throws:
      FileNotFoundException - if the file exists but is a directory rather than a regular file, does not exist but cannot be created, or cannot be opened for any other reason.
    • getOutputStream

      OutputStream getOutputStream(boolean append) throws FileNotFoundException
      Creates an output stream from a file name.
      Parameters:
      append - If true then data will be appended to the end of the file, if it already exists. If false and a normal file already exists with this name the file will first be truncated to zero length.
      Returns:
      an output stream suitable for writing to the file.
      Throws:
      FileNotFoundException - if the file exists but is a directory rather than a regular file, does not exist but cannot be created, or cannot be opened for any other reason.
    • getInputStream

      InputStream getInputStream() throws FileNotFoundException
      Creates an input stream from a file name.
      Returns:
      an input stream suitable for reading from the file.
      Throws:
      FileNotFoundException - if the file is not found.
    • getExclusiveFileLock

      int getExclusiveFileLock() throws StandardException
      Get an exclusive lock with this name. This is used to ensure that two or more JVMs do not open the same database at the same time. ny StorageFile that has getExclusiveFileLock() called on it is not intended to be read from or written to. It's sole purpose is to provide a locked entity to avoid multiple instances of Derby accessing the same database. getExclusiveFileLock() may delete or overwrite any existing file.
      Returns:
      EXCLUSIVE_FILE_LOCK_NOT_AVAILABLE if the lock cannot be acquired because it is already held.
      EXCLUSIVE_FILE_LOCK if the lock was successfully acquired.
      NO_FILE_LOCK_SUPPORT if the system does not support exclusive locks.
      Throws:
      StandardException
    • releaseExclusiveFileLock

      void releaseExclusiveFileLock()
      Release the resource associated with an earlier acquired exclusive lock releaseExclusiveFileLock() may delete the file
      See Also:
    • getRandomAccessFile

      StorageRandomAccessFile getRandomAccessFile(String mode) throws FileNotFoundException
      Get a random access file. This method is not called if the StorageFactory is read only. It is unspecified if the StorageFactory that created it is not a WritableStorageFactory.
      Parameters:
      mode - "r", "rw", "rws", or "rwd". The "rws" and "rwd" modes specify that the data is to be written to persistent store, consistent with the java.io.RandomAccessFile class ("synchronized" with the persistent storage, in the file system meaning of the word "synchronized"). However the implementation is not required to implement the "rws" or "rwd" modes. If the "rws" andr "rwd" modes are supported then the supportsRws() method of the StorageFactory returns true. If supportsRws() returns false then the implementation may treat "rws" and "rwd" as "rw". It is up to the user of this interface to call the StorageRandomAccessFile.sync method if necessary. However, if the "rws" or "rwd" modes are supported and the RandomAccessFile was opened in "rws" or "rwd" mode then the implementation of StorageRandomAccessFile.sync need not do anything.
      Returns:
      an object that can be used for random access to the file.
      Throws:
      IllegalArgumentException - if the mode argument is not equal to one of "r", "rw", "rws", or "rwd".
      FileNotFoundException - if the file exists but is a directory rather than a regular file, or cannot be opened or created for any other reason .
      See Also:
    • limitAccessToOwner

      void limitAccessToOwner() throws IOException
      Use when creating a new file. By default, a file created in an underlying file system, if applicable, will have read and write access for the file owner unless the property derby.useDefaultFilePermissions is set to true.
      Throws:
      IOException