log4j 2 adding multiple colors to console appender

Question

Hi I just downloaded and configured log4j-2. I am stuck on applying color codes to the SlowConsole console appender. My console appender is like below.

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN">
    <Appenders>
        <Console name="Console" target="SYSTEM_OUT">
            <PatternLayout pattern="%d{HH:mm:ss.SSS} %-5level %logger{36} - %msg%n"/>
        </Console>
        <Console name="SlowConsole" target="SYSTEM_OUT">
            <PatternLayout pattern="%highlight{%d{HH:mm:ss.SSS} %-5level %logger{36}.%M() @%L - %msg%n}{FATAL=red, ERROR=red, WARN=yellow, INFO=black, DEBUG=green, TRACE=blue}"/>
        </Console>
        <File name="File" fileName="C:\log\out.txt">
            <PatternLayout pattern="%d{HH:mm:ss.SSS} %-5level %logger{36} - %msg%n" />
        </File>
    </Appenders>
    <Loggers>
        <logger name="org.abc.ea.web" level="ALL" additivity="false">
            <!--Log4j for the WEB MODULE -->
            <appender-ref ref="SlowConsole"/>
        </logger>
        <logger name="org.abc.ea.ejb" level="ALL" additivity="false">
            <!--Log4j for the EJB MODULE -->
            <appender-ref ref="SlowConsole"/>
        </logger>
        <Root level="ERROR">
            <AppenderRef ref="Console"/>
            <AppenderRef ref="File" />
        </Root>
    </Loggers>
</Configuration>

I have two questions,

1. I am new to log4j, is this the right way to write xml config file?

2. How can i add two color codes to each log level?

   for example: DEBUG=green -> will output light green font, But i need it to be dim and bold

Answer 1

I think I found the solution. I downloaded log4j2-core-sources.jar and traced the source. You can write it as below;

<Console name="SlowConsole" target="SYSTEM_OUT">
     <PatternLayout disableAnsi="false"  pattern="%highlight{%d{HH:mm:ss.SSS} %-5level %logger{36}.%M() @%L - %msg%n}{FATAL=red blink, ERROR=red, WARN=yellow bold, INFO=black, DEBUG=green bold, TRACE=blue}"/>
</Console>

I think log4j2 documentation and its examples may need to be updated.

Answer 2

For a log4j2 colored output that looks very close to Spring Boot's default logback console output:

    <Console name="ConsoleAppender" target="SYSTEM_OUT" follow="true">
        <PatternLayout pattern="%d{${LOG_DATEFORMAT_PATTERN:-yyyy-MM-dd HH:mm:ss.SSS}} %highlight{${LOG_LEVEL_PATTERN:-%5p}}{FATAL=red blink, ERROR=red, WARN=yellow bold, INFO=green, DEBUG=green bold, TRACE=blue} %style{${sys:PID}}{magenta} [%15.15t] %style{%-40.40C{1.}}{cyan} : %m%n${LOG_EXCEPTION_CONVERSION_WORD:-%wEx}"/>
    </Console>

Answer 3

When using the eclipse console, its nice to see errors in red and all other logs in black. You can do this using Filters:

<Appenders>
    <Console name="ConsoleStdOut" target="SYSTEM_OUT">
        <ThresholdFilter level="ERROR" onMatch="DENY" onMismatch="ACCEPT"/>
        <PatternLayout pattern="%d{HH:mm:ss} [%t] %-5level %logger{36} - %msg%n" />
    </Console>
    <Console name="ConsoleStdErr" target="SYSTEM_ERR">
        <ThresholdFilter level="ERROR" onMatch="ACCEPT" onMismatch="DENY"/>
        <PatternLayout pattern="%d{HH:mm:ss} [%t] %-5level %logger{36} - %msg%n" />
    </Console>
</Appenders>
<Loggers>
    <Root level="info">
        <AppenderRef ref="ConsoleStdOut" />
        <AppenderRef ref="ConsoleStdErr" />
    </Root>
</Loggers>

Answer 4

Spring Boot style:

<Properties>
  <Property name="LOG_PATTERN">
    %d{yyyy-MM-dd HH:mm:ss.SSS} %highlight{${LOG_LEVEL_PATTERN:-%5p}}{FATAL=red, ERROR=red, WARN=yellow, INFO=green, DEBUG=green, TRACE=green} %style{${sys:PID}}{magenta} --- [%15.15t] %style{%-40.40c{1.}}{cyan} : %m%n%ex
  </Property>
</Properties>

<Appenders>
  <Console name="Console" target="SYSTEM_OUT">
    <PatternLayout pattern="${LOG_PATTERN}"/>
  </Console>
</Appenders>

Answer 5

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN">
    <Appenders>
        <Console name="Console" target="SYSTEM_OUT" follow="true">
            <PatternLayout
                    pattern="%clr{%d{yyyy-MM-dd HH:mm:ss.SSS}}{faint} %clr{%5p} %clr{${sys:PID}}{magenta} %clr{---}{faint} %clr{[%15.15t]}{faint} %clr{%-40.40c{1.}}{cyan} %clr{:}{faint} %m%n%xwEx"/>
        </Console>
    </Appenders>
    <Loggers>
        <Root level="info">
            <AppenderRef ref="Console"/>
        </Root>
    </Loggers>
</Configuration>

This worked in my Spring Boot application.

But I am not sure if it will work without Spring Boot.

Answer 6

1 : yes it's ok! and you can add some other options. see http://logging.apache.org/log4j/2.x/manual/configuration.html

2 : you can use a HTMLLayout for your file appender.

see http://logging.apache.org/log4j/2.x/manual/layouts.html

and http://www.tutorialspoint.com/log4j/log4j_htmllayout.htm

Answer 7

In log4j2 2.18.0 significant improvements were added in highlighting and generated ANSI code:

• 4 bit color support was added. Before 2.18.0 it was possible to use WARN=bright blue but generated ANSI code anyway used only 3 bit color palette and set font weight as bold. Now it is possible to use all 16 colors and besides to change font weight. For this purpose it is necessary to use bright_ prefix. For example WARN=bright_blue or with font weight WARN=bright_blue bold. For details see this issue

• true color support was added. For example, WARN=#00ff00. At the same time it is possible to change both foreground and background color. For details see this issue. For example:

  %highlight{%d [%t] %-5level: %msg%n%throwable}{FATAL=white, ERROR=red, WARN=bg_#5792e6 fg_#eef26b bold, INFO=black, DEBUG=#3fe0a8, TRACE=blue}