Display only selected Log4j debug statements

Question

Is it possible to display only those statements in console, which are having certain words.

For eq:

   logger.debug ( "java: hello " );
   logger.debug ( "groovy: hello " );
   logger.debug ( "ruby: hello " );

Now, by doing some configuration or whatever, all statements which are starting with groovy: should display.

Answer 1

You want to use the log4j StringMatchFilter which is part of the "extras" package from apache logging.

Here is a quick example found online :

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">
  <appender name="CustomAppender" class="org.apache.log4j.RollingFileAppender">
    <param name="File" value="custom.log"/>
    <param name="Append" value="true"/>
    <param name="MaxFileSize" value="5000KB"/>
    <param name="maxBackupIndex" value="5"/> 
          <layout class="org.apache.log4j.PatternLayout">
                  <param name="ConversionPattern" value="%d{yyyy-MM-dd HH:mm:ss} [%t] %-5p - %m%n" />
          </layout>

          <filter class="org.apache.log4j.varia.StringMatchFilter">
                  <param name="StringToMatch" value="Here is DEBUG" />
                  <param name="AcceptOnMatch" value="true" />
          </filter>

          <filter class="org.apache.log4j.varia.DenyAllFilter"/>
  </appender>

  <root>
    <appender-ref ref="CustomAppender"/>
  </root>
</log4j:configuration>

Answer 2

What about create your customs Levels

public class Groovy extends Level

And then in the log properties file set those levels as your configuration

Hope this helps, David.

Answer 3

One can use different loggers (say a logger for "java" messages and one for "groovy" messages). The Log4J configuration can be set with different levels for each logger.

You can read more here

Answer 4

One could use a tool to filter out messages. For Windows you could do this with BareTail . Filtering of messages is only possible with the pro (paid) version. Perhaps there are others tools that do the same job.

Answer 5

SLF4J markers are perhaps suitable for your purposes. All printing methods such as debug and info in org.slf4j.Logger admit a Marker as a first parameter . Moreover, logback-classic, a native SLF4J implementation, ships with a filter called MarkerFilter which I think does what you want.