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java.lang.Object org.apache.log4j.AppenderSkeleton org.apache.log4j.WriterAppender
public class WriterAppender
WriterAppender appends log events to a Writer
or an
OutputStream
depending on the user's choice.
Field Summary | |
---|---|
protected String |
encoding
The encoding to use when writing. |
protected boolean |
immediateFlush
Immediate flush means that the underlying writer or output stream will be flushed at the end of each append operation unless shouldFlush() is overridden. |
protected QuietWriter |
qw
This is the quietWriter where we will write
to. |
Fields inherited from class org.apache.log4j.AppenderSkeleton |
---|
closed, errorHandler, headFilter, layout, name, tailFilter, threshold |
Constructor Summary | |
---|---|
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 . |
Method Summary | |
---|---|
void |
activateOptions()
Does nothing. |
void |
append(LoggingEvent event)
This method is called by the AppenderSkeleton.doAppend(org.apache.log4j.spi.LoggingEvent)
method. |
protected boolean |
checkEntryConditions()
This method determines if there is a sense in attempting to append. |
void |
close()
Close this appender instance. |
protected void |
closeWriter()
Close the underlying Writer . |
protected OutputStreamWriter |
createWriter(OutputStream os)
Returns an OutputStreamWriter when passed an OutputStream. |
String |
getEncoding()
|
boolean |
getImmediateFlush()
Returns value of the ImmediateFlush option. |
boolean |
requiresLayout()
The WriterAppender requires a layout. |
protected void |
reset()
Clear internal references to the writer and other variables. |
void |
setEncoding(String value)
|
void |
setErrorHandler(ErrorHandler eh)
Set the ErrorHandler for this WriterAppender and also the
underlying QuietWriter if any. |
void |
setImmediateFlush(boolean value)
If the ImmediateFlush option is set to true , the appender will flush at the end of each
write. |
void |
setWriter(Writer writer)
Sets the Writer where the log output will go. |
protected boolean |
shouldFlush(LoggingEvent event)
Determines whether the writer should be flushed after this event is written. |
protected void |
subAppend(LoggingEvent event)
Actual writing occurs here. |
protected void |
writeFooter()
Write a footer as produced by the embedded layout's Layout.getFooter() method. |
protected void |
writeHeader()
Write a header as produced by the embedded layout's Layout.getHeader() method. |
Methods inherited from class org.apache.log4j.AppenderSkeleton |
---|
addFilter, clearFilters, doAppend, finalize, getErrorHandler, getFilter, getFirstFilter, getLayout, getName, getThreshold, isAsSevereAsThreshold, setLayout, setName, setThreshold |
Methods inherited from class java.lang.Object |
---|
clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Field Detail |
---|
protected boolean immediateFlush
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.
protected String encoding
The
encoding
variable is set to null by
default which results in the utilization of the system's default
encoding.
protected QuietWriter qw
quietWriter
where we will write
to.
Constructor Detail |
---|
public WriterAppender()
public WriterAppender(Layout layout, OutputStream os)
OutputStreamWriter
initialized with os
as its OutputStream
.
public WriterAppender(Layout layout, Writer writer)
writer
.
The writer
must have been previously opened by
the user.
Method Detail |
---|
public void setImmediateFlush(boolean value)
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.
public boolean getImmediateFlush()
public void activateOptions()
activateOptions
in interface OptionHandler
activateOptions
in class AppenderSkeleton
public void append(LoggingEvent event)
AppenderSkeleton.doAppend(org.apache.log4j.spi.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 class AppenderSkeleton
protected boolean checkEntryConditions()
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.
public void close()
Closed appenders cannot be reused.
setWriter(java.io.Writer)
protected void closeWriter()
Writer
.
protected OutputStreamWriter createWriter(OutputStream os)
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.
public String getEncoding()
public void setEncoding(String value)
public void setErrorHandler(ErrorHandler eh)
ErrorHandler
for this WriterAppender and also the
underlying QuietWriter
if any.
setErrorHandler
in interface Appender
setErrorHandler
in class AppenderSkeleton
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.protected void subAppend(LoggingEvent event)
Most subclasses of WriterAppender
will need to
override this method.
public boolean requiresLayout()
true
.
protected void reset()
protected void writeFooter()
Layout.getFooter()
method.
protected void writeHeader()
Layout.getHeader()
method.
protected boolean shouldFlush(LoggingEvent event)
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