lucene4.7源码研究之索引建立过程(1)

Directory整体流程还是比较简单的，图片借用

Directory directory = FSDirectory.open(file);

/** Creates an FSDirectory instance, trying to pick the
*  best implementation given the current environment.
*  The directory returned uses the {@link NativeFSLockFactory}.
*
*  <p>Currently this returns {@link MMapDirectory} for most Solaris
*  and Windows 64-bit JREs, {@link NIOFSDirectory} for other
*  non-Windows JREs, and {@link SimpleFSDirectory} for other
*  JREs on Windows. It is highly recommended that you consult the
*  implementation's documentation for your platform before
*  using this method.
*
* <p><b>NOTE</b>: this method may suddenly change which
* implementation is returned from release to release, in
* the event that higher performance defaults become
* possible; if the precise implementation is important to
* your application, please instantiate it directly,
* instead. For optimal performance you should consider using
* {@link MMapDirectory} on 64 bit JVMs.
*
* <p>See <a href="#subclasses">above</a> */
public static FSDirectory open(File path) throws IOException {
return open(path, null);//使用默认锁工厂
}

/** Just like {@link #open(File)}, but allows you to
*  also specify a custom {@link LockFactory}. */
public static FSDirectory open(File path, LockFactory lockFactory) throws IOException {
if ((Constants.WINDOWS || Constants.SUN_OS || Constants.LINUX)
&& Constants.JRE_IS_64BIT && MMapDirectory.UNMAP_SUPPORTED) {
return new MMapDirectory(path, lockFactory);
} else if (Constants.WINDOWS) {
return new SimpleFSDirectory(path, lockFactory);
} else {
return new NIOFSDirectory(path, lockFactory);
}
}

以NIOFSDirectory为例

/** Create a new NIOFSDirectory for the named location.
*
* @param path the path of the directory
* @param lockFactory the lock factory to use, or null for the default
* ({@link NativeFSLockFactory});
* @throws IOException if there is a low-level I/O error
*/
public NIOFSDirectory(File path, LockFactory lockFactory) throws IOException {
super(path, lockFactory);
}

/** Create a new FSDirectory for the named location (ctor for subclasses).
* @param path the path of the directory
* @param lockFactory the lock factory to use, or null for the default
* ({@link NativeFSLockFactory});
* @throws IOException if there is a low-level I/O error
*/
protected FSDirectory(File path, LockFactory lockFactory) throws IOException {
// new ctors use always NativeFSLockFactory as default:
if (lockFactory == null) {
lockFactory = new NativeFSLockFactory();
}
directory = getCanonicalPath(path);//获取path绝对路径

if (directory.exists() && !directory.isDirectory())
throw new NoSuchDirectoryException("file '" + directory + "' exists but is not a directory");

setLockFactory(lockFactory);//设置锁工厂

}

/**
* Create a NativeFSLockFactory instance, with null (unset)
* lock directory. When you pass this factory to a {@link FSDirectory}
* subclass, the lock directory is automatically set to the
* directory itself. Be sure to create one instance for each directory
* your create!
*/
public NativeFSLockFactory() {
this((File) null);//工厂没有设置路径
}

@Override
public void setLockFactory(LockFactory lockFactory) throws IOException {
super.setLockFactory(lockFactory);

// for filesystem based LockFactory, delete the lockPrefix, if the locks are placed
// in index dir. If no index dir is given, set ourselves
if (lockFactory instanceof FSLockFactory) {
final FSLockFactory lf = (FSLockFactory) lockFactory;
final File dir = lf.getLockDir();//因为（File）null，所以dir为null
// if the lock factory has no lockDir set, use the this directory as lockDir
if (dir == null) {
lf.setLockDir(directory);//使用我们设置的directory
lf.setLockPrefix(null);
} else if (dir.getCanonicalPath().equals(directory.getCanonicalPath())) {
lf.setLockPrefix(null);
}
}

}

整个open的过程其实就是在简单的定位lockFactory中setLockDir()，并且设置lockID

BaseDirectory

@Override
public String toString() {
return getClass().getSimpleName() + '@' + Integer.toHexString(hashCode()) + " lockFactory=" + getLockFactory();
}