org.apache.log4j
Class WriterAppender
- Appender, OptionHandler
public class WriterAppender
WriterAppender appends log events to a
Writer
or an
OutputStream
depending on the user's choice.
protected String | encoding - The encoding to use when opening an InputStream.
|
protected boolean | immediateFlush - Immediate flush means that the underlying writer or output stream
will be flushed at the end of each append operation.
|
protected QuietWriter | qw - This is the
quietWriter where we will write
to.
|
WriterAppender() - This default constructor does nothing.
|
WriterAppender(Layout layout, OutputStream os) - Instantiate a WriterAppender and set the output destination to a
new
OutputStreamWriter initialized with os
as its OutputStream .
|
WriterAppender(Layout layout, Writer writer) - Instantiate a WriterAppender and set the output destination to
writer .
|
activateOptions , addFilter , append , clearFilters , doAppend , finalize , getErrorHandler , getFilter , getFirstFilter , getLayout , getName , getThreshold , isAsSevereAsThreshold , setErrorHandler , setLayout , setName , setThreshold |
encoding
protected String encoding
The encoding to use when opening an InputStream.
The
encoding
variable is set to
null by
default which results in the utilization of the system's default
encoding.
immediateFlush
protected boolean immediateFlush
Immediate flush means that the underlying writer or output stream
will be flushed at the end of each append operation. Immediate
flush is slower but ensures that each append request is actually
written. If
immediateFlush
is set to
false
, then there is a good chance that the last few
logs events are not actually written to persistent media if and
when the application crashes.
The
immediateFlush
variable is set to
true
by default.
WriterAppender
public WriterAppender()
This default constructor does nothing.
WriterAppender
public WriterAppender(Layout layout,
OutputStream os)
Instantiate a WriterAppender and set the output destination to a
new OutputStreamWriter
initialized with os
as its OutputStream
.
WriterAppender
public WriterAppender(Layout layout,
Writer writer)
Instantiate a WriterAppender and set the output destination to
writer
.
The
writer
must have been previously opened by
the user.
append
public void append(LoggingEvent event)
This method is called by the
AppenderSkeleton.doAppend(LoggingEvent)
method.
If the output stream exists and is writable then write a log
statement to the output stream. Otherwise, write a single warning
message to
System.err
.
The format of the output will depend on this appender's
layout.
- append in interface AppenderSkeleton
checkEntryConditions
protected boolean checkEntryConditions()
This method determines if there is a sense in attempting to append.
It checks whether there is a set output target and also if
there is a set layout. If these checks fail, then the boolean
value
false
is returned.
close
public void close()
Close this appender instance. The underlying stream or writer is
also closed.
Closed appenders cannot be reused.
- close in interface Appender
closeWriter
protected void closeWriter()
createWriter
protected OutputStreamWriter createWriter(OutputStream os)
Returns an OutputStreamWriter when passed an OutputStream. The
encoding used will depend on the value of the
encoding
property. If the encoding value is
specified incorrectly the writer will be opened using the default
system encoding (an error message will be printed to the loglog.
getEncoding
public String getEncoding()
getImmediateFlush
public boolean getImmediateFlush()
Returns value of the ImmediateFlush option.
requiresLayout
public boolean requiresLayout()
The WriterAppender requires a layout. Hence, this method returns
true
.
- requiresLayout in interface Appender
reset
protected void reset()
Clear internal references to the writer and other variables.
Subclasses can override this method for an alternate closing
behavior.
setEncoding
public void setEncoding(String value)
setImmediateFlush
public void setImmediateFlush(boolean value)
If the
ImmediateFlush option is set to
true
, the appender will flush at the end of each
write. This is the default behavior. If the option is set to
false
, then the underlying stream can defer writing
to physical medium to a later time.
Avoiding the flush operation at the end of each append results in
a performance gain of 10 to 20 percent. However, there is safety
tradeoff involved in skipping flushing. Indeed, when flushing is
skipped, then it is likely that the last few log events will not
be recorded on disk when the application exits. This is a high
price to pay even for a 20% performance gain.
setWriter
public void setWriter(Writer writer)
Sets the Writer where the log output will go. The
specified Writer must be opened by the user and be
writable.
The
java.io.Writer
will be closed when the
appender instance is closed.
WARNING: Logging to an unopened Writer will fail.
writer
- An already opened Writer.
subAppend
protected void subAppend(LoggingEvent event)
Actual writing occurs here.
Most subclasses of
WriterAppender
will need to
override this method.
writeFooter
protected void writeFooter()
writeHeader
protected void writeHeader()
Copyright 2000-2005 Apache Software Foundation.