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.

N.B. the lock file is deleted when close() is called - or if the main file cannot be opened initially. In the (unlikely) event that the lockfile cannot be deleted, this is not reported, and subsequent requests using the same lockfile will fail.

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.

Field Summary

Fields inherited from class java.io.Writer

lock

Constructor Summary

Constructors

Constructor and Description
LockableFileWriter(File file) Constructs a LockableFileWriter.
LockableFileWriter(File file, boolean append) Constructs a LockableFileWriter.
LockableFileWriter(File file, boolean append, String lockDir) Deprecated. 2.5 use LockableFileWriter(File, Charset, boolean, String) instead
LockableFileWriter(File file, Charset charset) Constructs a LockableFileWriter with a file encoding.
LockableFileWriter(File file, Charset charset, boolean append, String lockDir) Constructs a LockableFileWriter with a file encoding.
LockableFileWriter(File file, String charsetName) Constructs a LockableFileWriter with a file encoding.
LockableFileWriter(File file, String charsetName, boolean append, String lockDir) Constructs a LockableFileWriter with a file encoding.
LockableFileWriter(String fileName) Constructs a LockableFileWriter.
LockableFileWriter(String fileName, boolean append) Constructs a LockableFileWriter.
LockableFileWriter(String fileName, boolean append, String lockDir) Constructs a LockableFileWriter.

Method Summary

Modifier and Type	Method and Description
void	close() Closes the file writer and deletes the lockfile (if possible).
void	flush() Flush the stream.
void	write(char[] chr) Write the characters from an array.
void	write(char[] chr, int st, int end) Write the specified characters from an array.
void	write(int idx) Write a character.
void	write(String str) Write the characters from a string.
void	write(String str, int st, int end) Write 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

Constructor Detail

LockableFileWriter

public LockableFileWriter(String fileName)
                   throws IOException

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

public LockableFileWriter(String fileName,
                          boolean append)
                   throws IOException

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

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

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

LockableFileWriter

public LockableFileWriter(File file)
                   throws IOException

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

public LockableFileWriter(File file,
                          boolean append)
                   throws IOException

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. 2.5 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

public LockableFileWriter(File file,
                          Charset charset)
                   throws IOException

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

public LockableFileWriter(File file,
                          String charsetName)
                   throws IOException

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

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

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

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

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.

Method Detail

close

public void close()
           throws IOException

Closes the file writer and deletes the lockfile (if possible).

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Specified by:

close in class Writer

Throws:

IOException - if an I/O error occurs

write

public void write(int idx)
           throws IOException

Write a character.

Overrides:

write in class Writer

Parameters:

idx - the character to write

Throws:

IOException - if an I/O error occurs

write

public void write(char[] chr)
           throws IOException

Write the characters from an array.

Overrides:

write in class Writer

Parameters:

chr - the characters to write

Throws:

IOException - if an I/O error occurs

write

public void write(char[] chr,
                  int st,
                  int end)
           throws IOException

Write the specified characters from an array.

Specified by:

write in class Writer

Parameters:

chr - the characters to write

st - The start offset

end - The number of characters to write

Throws:

IOException - if an I/O error occurs

write

public void write(String str)
           throws IOException

Write 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 st,
                  int end)
           throws IOException

Write the specified characters from a string.

Overrides:

write in class Writer

Parameters:

str - the string to write

st - The start offset

end - The number of characters to write

Throws:

IOException - if an I/O error occurs

flush

public void flush()
           throws IOException

Flush the stream.

Specified by:

flush in interface Flushable

Specified by:

flush in class Writer

Throws:

IOException - if an I/O error occurs