Package org.apache.lucene.store

Class Directory

java.lang.Object
org.apache.lucene.store.Directory
All Implemented Interfaces:
Closeable, AutoCloseable
Direct Known Subclasses:
BaseDirectory, CompoundDirectory, FileSwitchDirectory, FilterDirectory
public abstract class Directory extends Object implements Closeable
A Directory provides an abstraction layer for storing a list of files. A directory contains only files (no sub-folder hierarchy).

Implementing classes must comply with the following:

See Also:

  • Constructor Details

    • Directory

      public Directory()

  • Method Details

    • listAll

      public abstract String[] listAll() throws IOException
      Returns names of all files stored in this directory. The output must be in sorted (UTF-16, java's String.compareTo(java.lang.String)) order.
      Throws:
      IOException - in case of I/O error

    • deleteFile

      public abstract void deleteFile(String name) throws IOException
      Removes an existing file in the directory.

      This method must throw either NoSuchFileException or FileNotFoundException if name points to a non-existing file.

      Parameters:
      name - the name of an existing file.
      Throws:
      IOException - in case of I/O error

    • fileLength

      public abstract long fileLength(String name) throws IOException
      Returns the byte length of a file in the directory.

      This method must throw either NoSuchFileException or FileNotFoundException if name points to a non-existing file.

      Parameters:
      name - the name of an existing file.
      Throws:
      IOException - in case of I/O error

    • createOutput

      public abstract IndexOutput createOutput(String name, IOContext context) throws IOException
      Creates a new, empty file in the directory and returns an IndexOutput instance for appending data to this file.

      This method must throw FileAlreadyExistsException if the file already exists.

      Parameters:
      name - the name of the file to create.
      Throws:
      IOException - in case of I/O error

    • createTempOutput

      public abstract IndexOutput createTempOutput(String prefix, String suffix, IOContext context) throws IOException
      Creates a new, empty, temporary file in the directory and returns an IndexOutput instance for appending data to this file.

      The temporary file name (accessible via IndexOutput.getName()) will start with prefix, end with suffix and have a reserved file extension .tmp.

      Throws:
      IOException

    • sync

      public abstract void sync(Collection<String> names) throws IOException
      Ensures that any writes to these files are moved to stable storage (made durable).

      Lucene uses this to properly commit changes to the index, to prevent a machine/OS crash from corrupting the index.

      Throws:
      IOException
      See Also:

    • syncMetaData

      public abstract void syncMetaData() throws IOException
      Ensures that directory metadata, such as recent file renames, are moved to stable storage.
      Throws:
      IOException
      See Also:

    • rename

      public abstract void rename(String source, String dest) throws IOException
      Renames source file to dest file where dest must not already exist in the directory.

      It is permitted for this operation to not be truly atomic, for example both source and dest can be visible temporarily in listAll(). However, the implementation of this method must ensure the content of dest appears as the entire source atomically. So once dest is visible for readers, the entire content of previous source is visible.

      This method is used by IndexWriter to publish commits.

      Throws:
      IOException

    • openInput

      public abstract IndexInput openInput(String name, IOContext context) throws IOException
      Opens a stream for reading an existing file.

      This method must throw either NoSuchFileException or FileNotFoundException if name points to a non-existing file.

      Parameters:
      name - the name of an existing file.
      Throws:
      IOException - in case of I/O error

    • openChecksumInput

      public ChecksumIndexInput openChecksumInput(String name, IOContext context) throws IOException
      Opens a checksum-computing stream for reading an existing file.

      This method must throw either NoSuchFileException or FileNotFoundException if name points to a non-existing file.

      Parameters:
      name - the name of an existing file.
      Throws:
      IOException - in case of I/O error

    • obtainLock

      public abstract Lock obtainLock(String name) throws IOException
      Acquires and returns a Lock for a file with the given name.
      Parameters:
      name - the name of the lock file
      Throws:
      LockObtainFailedException - (optional specific exception) if the lock could not be obtained because it is currently held elsewhere.
      IOException - if any i/o error occurs attempting to gain the lock

    • close

      public abstract void close() throws IOException
      Closes the directory.
      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable
      Throws:
      IOException

    • copyFrom

      public void copyFrom(Directory from, String src, String dest, IOContext context) throws IOException
      Copies an existing src file from directory from to a non-existent file dest in this directory.
      Throws:
      IOException

    • toString

      public String toString()
      Overrides:
      toString in class Object

    • ensureOpen

      protected void ensureOpen() throws AlreadyClosedException
      Ensures this directory is still open.
      Throws:
      AlreadyClosedException - if this directory is closed.

    • getPendingDeletions

      public abstract Set<String> getPendingDeletions() throws IOException
      Returns a set of files currently pending deletion in this directory.
      Throws:
      IOException
      NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

    • getTempFileName

      protected static String getTempFileName(String prefix, String suffix, long counter)
      Creates a file name for a temporary file. The name will start with prefix, end with suffix and have a reserved file extension .tmp.
      See Also: