Grouping by parentheses as explained above allows coloring of sub-patterns. As of version 1.0.5, PatternLayout recognizes "%black", "%red", "%green","%yellow","%blue", "%magenta","%cyan", "%white", "%gray", "%boldRed","%boldGreen", "%boldYellow", "%boldBlue", "%boldMagenta""%boldCyan", "%boldWhite" and "%highlight" as conversion words. These conversion words are intended to contain a sub-pattern. Any sub-pattern enclosed by a coloring word will be output in the specified color.
Below is a configuration file illustrating coloring. Note the %cyan conversion specifier enclosing "%logger{15}". This will output the logger name abbreviated to 15 characters in cyan. The %highlight conversion specifier prints its sub-pattern in bold-red for events of level ERROR, in red for WARN, in BLUE for INFO, and in the default color for other levels.
Example: Highlighting levels (logback-examples/src/main/java/chapters/layouts/highlighted.xml) View as .groovy
<configuration debug="true">
<appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
<!-- On Windows machines setting withJansi to true enables ANSI
color code interpretation by the Jansi library. This requires
org.fusesource.jansi:jansi:1.8 on the class path. Note that
Unix-based operating systems such as Linux and Mac OS X
support ANSI color codes by default. -->
<withjansi>true</withJansi>
<encoder>
<pattern>[%thread] %highlight(%-5level) %cyan(%logger{15}) - %msg %n</pattern>
</encoder>
</appender>
<root level="DEBUG">
<appender-ref ref="STDOUT" />
</root>
</configuration>
Here is the corresponding output:
[main] WARN c.l.TrivialMain - a warning message 0
[main] DEBUG c.l.TrivialMain - hello world number1
[main] DEBUG c.l.TrivialMain - hello world number2
[main] INFO c.l.TrivialMain - hello world number3
[main] DEBUG c.l.TrivialMain - hello world number4
[main] WARN c.l.TrivialMain - a warning message 5
[main] ERROR c.l.TrivialMain - Finish off with fireworks
It takes very few lines of code to create a coloring conversion word. The section entitled creating a custom conversion specifier discusses the steps necessary for registering a conversion word in your configuration file.
