Java Logger - Logback

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Configuration

http://logback.qos.ch/manual/configuration.html

example

<configuration>

  <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
    <encoder>
      <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>
    </encoder>
  </appender>

  <logger name="com.mchange.v2" level="warn"/>
  <logger name="io.netty" level="warn"/>
  <logger name="io.vertx" level="info"/>
  <logger name="net.bytle" level="warn"/>

  <root level="debug">
    <appender-ref ref="STDOUT"/>
  </root>

</configuration>

where, there is:

one appender that write to the console with the message format %d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n
several logger that gets their level.
the root logger gets the debug level and the console appender. All other logger will inherit from it.

Set the configuration file

at the command line

java -Dlogback.configurationFile=/path/to/config.xml chapters.configuration.MyApp1

in the code

import ch.qos.logback.classic.util.ContextInitializer;

public class ServerMain {
    public static void main(String args[]) throws IOException, InterruptedException {
       // must be set before the first call to  LoggerFactory.getLogger();
       // ContextInitializer.CONFIG_FILE_PROPERTY is set to "logback.configurationFile"
       System.setProperty(ContextInitializer.CONFIG_FILE_PROPERTY, "/path/to/config.xml");
       ...
    }   
}

Rescan

<configuration scan="true" scanPeriod="30 seconds" > 
  ... 
</configuration>

Logger

Parameterized message

With a parameterized message only after evaluating whether to log or not, and only if the decision is positive, will the logger implementation format the message and replace the '{}' pair with the string value of entry. In other words, this form does not incur the cost of parameter construction when the log statement is disabled.

logger.debug("The entry is {}.", entry);

// or

logger.debug("The new entry is {}. It replaces {}.", entry, oldEntry);

// or

Object[] paramArray = {newVal, below, above};
logger.debug("Value {} was inserted between {} and {}.", paramArray);

Configuring logger

Configuring loggers, or the

element]]

One appender use on the root and chapters.configuration logger

<configuration>

  <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
    <encoder>
      <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>
    </encoder>
  </appender>

  <logger name="chapters.configuration">
    <appender-ref ref="STDOUT" />
  </logger>

  <root level="debug">
    <appender-ref ref="STDOUT" />
  </root>
</configuration>

Appender

Java - Appender (or Handlers) in Logback

Doc

List:

DbAppender
CassandraAppender
SMTPAppender (Email)
RollingFile Appender - ie Log - Rotation

File Appender

Doc

<configuration>
  <appender name="fileAppender" class="ch.qos.logback.core.rolling.FileAppender">
    <file>my.log</file>
    <encoder>
      <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>
    </encoder>
  </appender>
  [...]
</configuration>

where:

my.log is the name of the file
pattern defines the message format

Documentation / Reference

http://logback.qos.ch/