Package org.apache.log4j

Class WriterAppender

    • Field Detail

      • immediateFlush

        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. 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.

      • encoding

        protected java.lang.String encoding
        The encoding to use when writing.

        The encoding variable is set to null by default which results in the utilization of the system's default encoding.

    • Constructor Detail

      • WriterAppender

        public WriterAppender()
        This default constructor does nothing.

      • WriterAppender

        public WriterAppender​(Layout layout,
                      java.io.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,
                      java.io.Writer writer)
        Instantiate a WriterAppender and set the output destination to writer.

        The writer must have been previously opened by the user.

    • Method Detail

      • 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.

      • getImmediateFlush

        public boolean getImmediateFlush()
        Returns value of the ImmediateFlush option.

      • 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.

        Since:
        0.8.4
        See Also:
        setWriter(java.io.Writer)

      • closeWriter

        protected void closeWriter()
        Close the underlying Writer.

      • createWriter

        protected java.io.OutputStreamWriter createWriter​(java.io.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 java.lang.String getEncoding()

      • setEncoding

        public void setEncoding​(java.lang.String value)

      • setWriter

        public void setWriter​(java.io.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.

        Parameters:
        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.

        Since:
        0.9.0

      • requiresLayout

        public boolean requiresLayout()
        The WriterAppender requires a layout. Hence, this method returns true.

      • reset

        protected void reset()
        Clear internal references to the writer and other variables.

        Subclasses can override this method for an alternate closing behavior.

      • writeFooter

        protected void writeFooter()
        Write a footer as produced by the embedded layout's Layout.getFooter() method.

      • writeHeader

        protected void writeHeader()
        Write a header as produced by the embedded layout's Layout.getHeader() method.

      • shouldFlush

        protected boolean shouldFlush​(LoggingEvent event)
        Determines whether the writer should be flushed after this event is written.
        Since:
        1.2.16