Package org.apache.commons.io.output

Class LockableFileWriter

java.lang.Object

java.io.Writer

org.apache.commons.io.output.LockableFileWriter

All Implemented Interfaces:

Closeable, Flushable, Appendable, AutoCloseable

public class LockableFileWriter
extends Writer

FileWriter that will create and honor lock files to allow simple cross thread file lock handling.

This class provides a simple alternative to FileWriter that will use a lock file to prevent duplicate writes.

Note: The lock file is deleted when close() is called - or if the main file cannot be opened initially. In the (unlikely) event that the lock file cannot be deleted, an exception is thrown.

By default, the file will be overwritten, but this may be changed to append. The lock directory may be specified, but defaults to the system property java.io.tmpdir. The encoding may also be specified, and defaults to the platform default.

To build an instance, use LockableFileWriter.Builder.

See Also:

• LockableFileWriter.Builder

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	LockableFileWriter.Builder	Builds a new LockableFileWriter.

Field Summary

Fields

Modifier and Type	Field	Description
private static final String	LCK	The extension for the lock file.
private final File	lockFile	The lock file.
private final Writer	out	The writer to decorate.

Fields inherited from class java.io.Writer

lock

Constructor Summary

Constructors

Constructor	Description
LockableFileWriter(File file)	Deprecated. Use builder(), LockableFileWriter.Builder, and LockableFileWriter.Builder.get()
LockableFileWriter(File file, boolean append)	Deprecated. Use builder(), LockableFileWriter.Builder, and LockableFileWriter.Builder.get()
LockableFileWriter(File file, boolean append, String lockDir)	Deprecated. Use LockableFileWriter(File, Charset, boolean, String) instead
LockableFileWriter(File file, String charsetName)	Deprecated. Use builder(), LockableFileWriter.Builder, and LockableFileWriter.Builder.get()
LockableFileWriter(File file, String charsetName, boolean append, String lockDir)	Deprecated. Use builder(), LockableFileWriter.Builder, and LockableFileWriter.Builder.get()
LockableFileWriter(File file, Charset charset)	Deprecated. Use builder(), LockableFileWriter.Builder, and LockableFileWriter.Builder.get()
LockableFileWriter(File file, Charset charset, boolean append, String lockDir)	Deprecated. Use builder(), LockableFileWriter.Builder, and LockableFileWriter.Builder.get()
LockableFileWriter(String fileName)	Deprecated. Use builder(), LockableFileWriter.Builder, and LockableFileWriter.Builder.get()
LockableFileWriter(String fileName, boolean append)	Deprecated. Use builder(), LockableFileWriter.Builder, and LockableFileWriter.Builder.get()
LockableFileWriter(String fileName, boolean append, String lockDir)	Deprecated. Use builder(), LockableFileWriter.Builder, and LockableFileWriter.Builder.get()

Method Summary

Modifier and Type	Method	Description
static LockableFileWriter.Builder	builder()	Constructs a new LockableFileWriter.Builder.
void	close()	Closes the file writer and deletes the lock file.
private void	createLock()	Creates the lock file.
void	flush()	Flushes the stream.
private Writer	initWriter(File file, Charset charset, boolean append)	Initializes the wrapped file writer.
private void	testLockDir(File lockDir)	Tests that we can write to the lock directory.
void	write(char[] cbuf)	Writes the characters from an array.
void	write(char[] cbuf, int off, int len)	Writes the specified characters from an array.
void	write(int c)	Writes a character.
void	write(String str)	Writes the characters from a string.
void	write(String str, int off, int len)	Writes the specified characters from a string.

Methods inherited from class java.io.Writer

append, append, append

Methods inherited from class java.lang.Object

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

Field Details

LCK

private static final String LCK

The extension for the lock file.

See Also:

• Constant Field Values

out

private final Writer out

The writer to decorate.

lockFile

private final File lockFile

The lock file.

Constructor Details

LockableFileWriter

@Deprecated
public LockableFileWriter(File file)
                   throws IOException

Deprecated.

Use builder(), LockableFileWriter.Builder, and LockableFileWriter.Builder.get()

Constructs a LockableFileWriter. If the file exists, it is overwritten.

Parameters:

file - the file to write to, not null

Throws:

NullPointerException - if the file is null

IOException - in case of an I/O error

LockableFileWriter

@Deprecated
public LockableFileWriter(File file,
 boolean append)
                   throws IOException

Deprecated.

Use builder(), LockableFileWriter.Builder, and LockableFileWriter.Builder.get()

Constructs a LockableFileWriter.

Parameters:

file - the file to write to, not null

append - true if content should be appended, false to overwrite

Throws:

NullPointerException - if the file is null

IOException - in case of an I/O error

LockableFileWriter

@Deprecated
public LockableFileWriter(File file,
 boolean append,
 String lockDir)
                   throws IOException

Deprecated.

Use LockableFileWriter(File, Charset, boolean, String) instead

Constructs a LockableFileWriter.

Parameters:

file - the file to write to, not null

append - true if content should be appended, false to overwrite

lockDir - the directory in which the lock file should be held

Throws:

NullPointerException - if the file is null

IOException - in case of an I/O error

LockableFileWriter

@Deprecated
public LockableFileWriter(File file,
 Charset charset)
                   throws IOException

Deprecated.

Use builder(), LockableFileWriter.Builder, and LockableFileWriter.Builder.get()

Constructs a LockableFileWriter with a file encoding.

Parameters:

file - the file to write to, not null

charset - the charset to use, null means platform default

Throws:

NullPointerException - if the file is null

IOException - in case of an I/O error

Since:

2.3

LockableFileWriter

@Deprecated
public LockableFileWriter(File file,
 Charset charset,
 boolean append,
 String lockDir)
                   throws IOException

Deprecated.

Use builder(), LockableFileWriter.Builder, and LockableFileWriter.Builder.get()

Constructs a LockableFileWriter with a file encoding.

Parameters:

file - the file to write to, not null

charset - the name of the requested charset, null means platform default

append - true if content should be appended, false to overwrite

lockDir - the directory in which the lock file should be held

Throws:

NullPointerException - if the file is null

IOException - in case of an I/O error

Since:

2.3

LockableFileWriter

@Deprecated
public LockableFileWriter(File file,
 String charsetName)
                   throws IOException

Deprecated.

Use builder(), LockableFileWriter.Builder, and LockableFileWriter.Builder.get()

Constructs a LockableFileWriter with a file encoding.

Parameters:

file - the file to write to, not null

charsetName - the name of the requested charset, null means platform default

Throws:

NullPointerException - if the file is null

IOException - in case of an I/O error

UnsupportedCharsetException - thrown instead of UnsupportedEncodingException in version 2.2 if the encoding is not supported.

LockableFileWriter

@Deprecated
public LockableFileWriter(File file,
 String charsetName,
 boolean append,
 String lockDir)
                   throws IOException

Deprecated.

Use builder(), LockableFileWriter.Builder, and LockableFileWriter.Builder.get()

Constructs a LockableFileWriter with a file encoding.

Parameters:

file - the file to write to, not null

charsetName - the encoding to use, null means platform default

append - true if content should be appended, false to overwrite

lockDir - the directory in which the lock file should be held

Throws:

NullPointerException - if the file is null

IOException - in case of an I/O error

UnsupportedCharsetException - thrown instead of UnsupportedEncodingException in version 2.2 if the encoding is not supported.

LockableFileWriter

@Deprecated
public LockableFileWriter(String fileName)
                   throws IOException

Deprecated.

Use builder(), LockableFileWriter.Builder, and LockableFileWriter.Builder.get()

Constructs a LockableFileWriter. If the file exists, it is overwritten.

Parameters:

fileName - the file to write to, not null

Throws:

NullPointerException - if the file is null

IOException - in case of an I/O error

LockableFileWriter

@Deprecated
public LockableFileWriter(String fileName,
 boolean append)
                   throws IOException

Deprecated.

Use builder(), LockableFileWriter.Builder, and LockableFileWriter.Builder.get()

Constructs a LockableFileWriter.

Parameters:

fileName - file to write to, not null

append - true if content should be appended, false to overwrite

Throws:

NullPointerException - if the file is null

IOException - in case of an I/O error

LockableFileWriter

@Deprecated
public LockableFileWriter(String fileName,
 boolean append,
 String lockDir)
                   throws IOException

Deprecated.

Use builder(), LockableFileWriter.Builder, and LockableFileWriter.Builder.get()

Constructs a LockableFileWriter.

Parameters:

fileName - the file to write to, not null

append - true if content should be appended, false to overwrite

lockDir - the directory in which the lock file should be held

Throws:

NullPointerException - if the file is null

IOException - in case of an I/O error

Method Details

builder

public static LockableFileWriter.Builder builder()

Constructs a new LockableFileWriter.Builder.

Returns:

a new LockableFileWriter.Builder.

Since:

2.12.0

close

public void close()
           throws IOException

Closes the file writer and deletes the lock file.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Specified by:

close in class Writer

Throws:

IOException - if an I/O error occurs.

createLock

private void createLock()
                 throws IOException

Creates the lock file.

Throws:

IOException - if we cannot create the file

flush

public void flush()
           throws IOException

Flushes the stream.

Specified by:

flush in interface Flushable

Specified by:

flush in class Writer

Throws:

IOException - if an I/O error occurs.

initWriter

private Writer initWriter(File file,
 Charset charset,
 boolean append)
                   throws IOException

Initializes the wrapped file writer. Ensure that a cleanup occurs if the writer creation fails.

Parameters:

file - the file to be accessed

charset - the charset to use

append - true to append

Returns:

The initialized writer

Throws:

IOException - if an error occurs

testLockDir

private void testLockDir(File lockDir)
                  throws IOException

Tests that we can write to the lock directory.

Parameters:

lockDir - the File representing the lock directory

Throws:

IOException - if we cannot write to the lock directory

IOException - if we cannot find the lock file

write

public void write(char[] cbuf)
           throws IOException

Writes the characters from an array.

Overrides:

write in class Writer

Parameters:

cbuf - the characters to write

Throws:

IOException - if an I/O error occurs.

write

public void write(char[] cbuf,
 int off,
 int len)
           throws IOException

Writes the specified characters from an array.

Specified by:

write in class Writer

Parameters:

cbuf - the characters to write

off - The start offset

len - The number of characters to write

Throws:

IOException - if an I/O error occurs.

write

public void write(int c)
           throws IOException

Writes a character.

Overrides:

write in class Writer

Parameters:

c - the character to write

Throws:

IOException - if an I/O error occurs.

write

public void write(String str)
           throws IOException

Writes the characters from a string.

Overrides:

write in class Writer

Parameters:

str - the string to write

Throws:

IOException - if an I/O error occurs.

write

public void write(String str,
 int off,
 int len)
           throws IOException

Writes the specified characters from a string.

Overrides:

write in class Writer

Parameters:

str - the string to write

off - The start offset

len - The number of characters to write

Throws:

IOException - if an I/O error occurs.