org.apache.commons.io.output
Class LockableFileWriter

java.lang.Object
  extended by java.io.Writer
      extended by org.apache.commons.io.output.LockableFileWriter
All Implemented Interfaces:
Closeable, Flushable, Appendable

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.

Version:
$Id: LockableFileWriter.java 1311756 2012-04-10 14:32:42Z ggregory $

Field Summary
 
Fields inherited from class java.io.Writer
lock
 
Constructor Summary
LockableFileWriter(File file)
          Constructs a LockableFileWriter.
LockableFileWriter(File file, boolean append)
          Constructs a LockableFileWriter.
LockableFileWriter(File file, boolean append, String lockDir)
          Constructs a LockableFileWriter.
LockableFileWriter(File file, Charset encoding)
          Constructs a LockableFileWriter with a file encoding.
LockableFileWriter(File file, Charset encoding, boolean append, String lockDir)
          Constructs a LockableFileWriter with a file encoding.
LockableFileWriter(File file, String encoding)
          Constructs a LockableFileWriter with a file encoding.
LockableFileWriter(File file, String encoding, 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
 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

public LockableFileWriter(File file,
                          boolean append,
                          String lockDir)
                   throws IOException
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 encoding)
                   throws IOException
Constructs a LockableFileWriter with a file encoding.

Parameters:
file - the file to write to, not null
encoding - the encoding 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 encoding)
                   throws IOException
Constructs a LockableFileWriter with a file encoding.

Parameters:
file - the file to write to, not null
encoding - the encoding to use, 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 encoding,
                          boolean append,
                          String lockDir)
                   throws IOException
Constructs a LockableFileWriter with a file encoding.

Parameters:
file - the file to write to, not null
encoding - 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
Since:
2.3

LockableFileWriter

public LockableFileWriter(File file,
                          String encoding,
                          boolean append,
                          String lockDir)
                   throws IOException
Constructs a LockableFileWriter with a file encoding.

Parameters:
file - the file to write to, not null
encoding - 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 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


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