org.h2.store

Class FileLock

java.lang.Object

org.h2.store.FileLock

All Implemented Interfaces:

Runnable

public class FileLock
extends Object
implements Runnable

The file lock is used to lock a database so that only one process can write to it. It uses a cooperative locking protocol. Usually a .lock.db file is used, but locking by creating a socket is supported as well.

Field Summary

Fields

Modifier and Type	Field and Description
static int	LOCK_FILE This locking method means the cooperative file locking protocol should be used.
static int	LOCK_FS Use the file system to lock the file; don't use a separate lock file.
static int	LOCK_NO This locking method means no locking is used at all.
static int	LOCK_SERIALIZED This locking method means multiple writers are allowed, and they synchronize themselves.
static int	LOCK_SOCKET This locking method means a socket is created on the given machine.

Constructor Summary

Constructors

Constructor and Description
FileLock(TraceSystem traceSystem, String fileName, int sleep) Create a new file locking object.

Method Summary

Methods

Modifier and Type	Method and Description
static int	getFileLockMethod(String method) Get the file locking method type given a method name.
String	getUniqueId()
Properties	load() Load the properties file.
void	lock(int fileLockMethod) Lock the file if possible.
void	run()
Properties	save() Save the lock file.
void	setProperty(String key, String value) Add or change a setting to the properties.
void	unlock() Unlock the file.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

LOCK_NO

public static final int LOCK_NO

This locking method means no locking is used at all.

See Also:

Constant Field Values

LOCK_FILE

public static final int LOCK_FILE

This locking method means the cooperative file locking protocol should be used.

See Also:

Constant Field Values

LOCK_SOCKET

public static final int LOCK_SOCKET

This locking method means a socket is created on the given machine.

See Also:

Constant Field Values

LOCK_SERIALIZED

public static final int LOCK_SERIALIZED

This locking method means multiple writers are allowed, and they synchronize themselves.

See Also:

Constant Field Values

LOCK_FS

public static final int LOCK_FS

Use the file system to lock the file; don't use a separate lock file.

See Also:

Constant Field Values

Constructor Detail

FileLock

public FileLock(TraceSystem traceSystem,
        String fileName,
        int sleep)

Create a new file locking object.

Parameters:

traceSystem - the trace system to use

fileName - the file name

sleep - the number of milliseconds to sleep

Method Detail

lock

public void lock(int fileLockMethod)

Lock the file if possible. A file may only be locked once.

Parameters:

fileLockMethod - the file locking method to use

Throws:

DbException - if locking was not successful

unlock

public void unlock()

Unlock the file. The watchdog thread is stopped. This method does nothing if the file is already unlocked.

setProperty

public void setProperty(String key,
               String value)

Add or change a setting to the properties. This call does not save the file.

Parameters:

key - the key

value - the value

save

public Properties save()

Save the lock file.

Returns:

the saved properties

load

public Properties load()

Load the properties file.

Returns:

the properties

getFileLockMethod

public static int getFileLockMethod(String method)

Get the file locking method type given a method name.

Parameters:

method - the method name

Returns:

the method type

Throws:

DbException - if the method name is unknown

getUniqueId

public String getUniqueId()

run

public void run()

Specified by:

run in interface Runnable