Log4j2: File Appender: Write log messages to a file

File appender writes log messages to a file. Following table explain the parameters of File appender.

Parameter	Type	Description
append	boolean	If set to true, records are appended to end of the file, else file will be cleared before writing new log messages.
bufferedIO	boolean	If it is set to true, records are written to a buffer and the data will be written to disk when the buffer is full or, if immediateFlush is set, when the record is written. Default value is true.
bufferSize	Int	Size of the buffer. Default value is 8192 bytes.
filter	Filter	Filters are used to filter the log events. Filters take the decision, whether to log the event (or) not. More than one Filter may be used by using a CompositeFilter.
fileName	String	Name of the file to write to. If the file (or), any of the parent directories do not exist, they will be created.
immediateFlush	boolean	Default value is true. If it is set to true, each write will be followed by a flush.
layout	Layout	The Layout to use to format the LogEvent.
locking	boolean	When set to true, I/O operations will occur only while the file lock is held allowing FileAppenders in multiple JVMs and potentially multiple hosts to write to the same file simultaneously. Default value is false.
ignoreExceptions	boolean	If set to false, exception are propagated to the caller, else exceptions encountered while appending events to be internally logged and then ignored. Default value is true.

log4j2.xml

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="DEBUG" monitorInterval="30">
 <Appenders>
  <Console name="my_console_appender" target="SYSTEM_OUT">
   <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n" />
  </Console>
  <File name="my_file_appender" fileName="/Users/harikrishna_gurram/application.log">
   <PatternLayout>
    <Pattern>%d %p %c{1.} [%t] %m%n</Pattern>
   </PatternLayout>
  </File>
 </Appenders>
 <Loggers>
  <Root level="info">
   <AppenderRef ref="my_console_appender" />
   <AppenderRef ref="my_file_appender" />
  </Root>
 </Loggers>
</Configuration>

package log4j_tutorial;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

public class HelloWorld {
 private static final Logger logger = LogManager.getLogger();

 public static void main(String args[]) {
  logger.trace("Trace Message!");
  logger.debug("Debug Message!");
  logger.info("Info Message!");
  logger.warn("Warn Message!");
  logger.error("Error Message!");
  logger.fatal("Fatal Message!");
 }
}

Run HelloWorld application, you can see following messages in /Users/harikrishna_gurram/application.log file.

2015-10-03 19:51:58,258 INFO l.HelloWorld [main] Info Message!

2015-10-03 19:51:58,259 WARN l.HelloWorld [main] Warn Message!

2015-10-03 19:51:58,259 ERROR l.HelloWorld [main] Error Message!
2015-10-03 19:51:58,259 FATAL l.HelloWorld [main] Fatal Message!

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