package org.apache.lucene.store;
/**
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.Closeable;
import java.util.Collection; // for javadocs
import org.apache.lucene.util.IOUtils;
/** A Directory is a flat list of files. Files may be written once, when they
* are created. Once a file is created it may only be opened for read, or
* deleted. Random access is permitted both when reading and writing.
*
* <p> Java's i/o APIs not used directly, but rather all i/o is
* through this API. This permits things such as: <ul>
* <li> implementation of RAM-based indices;
* <li> implementation indices stored in a database, via JDBC;
* <li> implementation of an index as a single file;
* </ul>
*
* Directory locking is implemented by an instance of {@link
* LockFactory}, and can be changed for each Directory
* instance using {@link #setLockFactory}.
*
*/
public abstract class Directory implements Closeable {
volatile protected boolean isOpen = true;
/** Holds the LockFactory instance (implements locking for
* this Directory instance). */
protected LockFactory lockFactory;
/**
* Returns an array of strings, one for each file in the directory.
*
* @throws NoSuchDirectoryException if the directory is not prepared for any
* write operations (such as {@link #createOutput(String)}).
* @throws IOException in case of other IO errors
*/
public abstract String[] listAll() throws IOException;
/** Returns true iff a file with the given name exists. */
public abstract boolean fileExists(String name)
throws IOException;
/** Returns the time the named file was last modified. */
public abstract long fileModified(String name)
throws IOException;
/** Set the modified time of an existing file to now. */
public abstract void touchFile(String name)
throws IOException;
/** Removes an existing file in the directory. */
public abstract void deleteFile(String name)
throws IOException;
/**
* Returns the length of a file in the directory. This method follows the
* following contract:
* <ul>
* <li>Throws {@link FileNotFoundException} if the file does not exist
* <li>Returns a value ≥0 if the file exists, which specifies its length.
* </ul>
*
* @param name the name of the file for which to return the length.
* @throws FileNotFoundException if the file does not exist.
* @throws IOException if there was an IO error while retrieving the file's
* length.
*/
public abstract long fileLength(String name) throws IOException;
/** Creates a new, empty file in the directory with the given name.
Returns a stream writing this file. */
public abstract IndexOutput createOutput(String name)
throws IOException;
/**
* Ensure that any writes to this file are moved to
* stable storage. Lucene uses this to properly commit
* changes to the index, to prevent a machine/OS crash
* from corrupting the index.
* @deprecated use {@link #sync(Collection)} instead.
* For easy migration you can change your code to call
* sync(Collections.singleton(name))
*/
@Deprecated
public void sync(String name) throws IOException { // TODO 4.0 kill me
}
/**
* Ensure that any writes to these files are moved to
* stable storage. Lucene uses this to properly commit
* changes to the index, to prevent a machine/OS crash
* from corrupting the index.<br/>
* <br/>
* NOTE: Clients may call this method for same files over
* and over again, so some impls might optimize for that.
* For other impls the operation can be a noop, for various
* reasons.
*/
public void sync(Collection<String> names) throws IOException { // TODO 4.0 make me abstract
for (String name : names)
sync(name);
}
/** Returns a stream reading an existing file. */
public abstract IndexInput openInput(String name)
throws IOException;
/** Returns a stream reading an existing file, with the
* specified read buffer size. The particular Directory
* implementation may ignore the buffer size. Currently
* the only Directory implementations that respect this
* parameter are {@link FSDirectory} and {@link
* org.apache.lucene.index.CompoundFileReader}.
*/
public IndexInput openInput(String name, int bufferSize) throws IOException {
return openInput(name);
}
/** Construct a {@link Lock}.
* @param name the name of the lock file
*/
public Lock makeLock(String name) {
return lockFactory.makeLock(name);
}
/**
* Attempt to clear (forcefully unlock and remove) the
* specified lock. Only call this at a time when you are
* certain this lock is no longer in use.
* @param name name of the lock to be cleared.
*/
public void clearLock(String name) throws IOException {
if (lockFactory != null) {
lockFactory.clearLock(name);
}
}
/** Closes the store. */
public abstract void close()
throws IOException;
/**
* Set the LockFactory that this Directory instance should
* use for its locking implementation. Each * instance of
* LockFactory should only be used for one directory (ie,
* do not share a single instance across multiple
* Directories).
*
* @param lockFactory instance of {@link LockFactory}.
*/
public void setLockFactory(LockFactory lockFactory) {
assert lockFactory != null;
this.lockFactory = lockFactory;
lockFactory.setLockPrefix(this.getLockID());
}
/**
* Get the LockFactory that this Directory instance is
* using for its locking implementation. Note that this
* may be null for Directory implementations that provide
* their own locking implementation.
*/
public LockFactory getLockFactory() {
return this.lockFactory;
}
/**
* Return a string identifier that uniquely differentiates
* this Directory instance from other Directory instances.
* This ID should be the same if two Directory instances
* (even in different JVMs and/or on different machines)
* are considered "the same index". This is how locking
* "scopes" to the right index.
*/
public String getLockID() {
return this.toString();
}
/**
* Copies the file <i>src</i> to {@link Directory} <i>to</i> under the new
* file name <i>dest</i>.
* <p>
* If you want to copy the entire source directory to the destination one, you
* can do so like this:
*
* <pre>
* Directory to; // the directory to copy to
* for (String file : dir.listAll()) {
* dir.copy(to, file, newFile); // newFile can be either file, or a new name
* }
* </pre>
* <p>
* <b>NOTE:</b> this method does not check whether <i>dest<i> exist and will
* overwrite it if it does.
*/
public void copy(Directory to, String src, String dest) throws IOException {
IndexOutput os = to.createOutput(dest);
IndexInput is = openInput(src);
IOException priorException = null;
try {
is.copyBytes(os, is.length());
} catch (IOException ioe) {
priorException = ioe;
} finally {
IOUtils.closeSafely(priorException, os, is);
}
}
/**
* Copy contents of a directory src to a directory dest. If a file in src
* already exists in dest then the one in dest will be blindly overwritten.
* <p>
* <b>NOTE:</b> the source directory cannot change while this method is
* running. Otherwise the results are undefined and you could easily hit a
* FileNotFoundException.
* <p>
* <b>NOTE:</b> this method only copies files that look like index files (ie,
* have extensions matching the known extensions of index files).
*
* @param src source directory
* @param dest destination directory
* @param closeDirSrc if <code>true</code>, call {@link #close()} method on
* source directory
* @deprecated should be replaced with calls to
* {@link #copy(Directory, String, String)} for every file that
* needs copying. You can use the following code:
*
* <pre>
* for (String file : src.listAll()) {
* src.copy(dest, file, file);
* }
* </pre>
*/
public static void copy(Directory src, Directory dest, boolean closeDirSrc) throws IOException {
for (String file : src.listAll()) {
src.copy(dest, file, file);
}
if (closeDirSrc) {
src.close();
}
}
/**
* @throws AlreadyClosedException if this Directory is closed
*/
protected final void ensureOpen() throws AlreadyClosedException {
if (!isOpen)
throw new AlreadyClosedException("this Directory is closed");
}
}