How to use Log4j2 xml Rewrite appender for modifying LogEvent before it logs in file

I want to use Rewrite appender in my log4j2.xml file so that before logging I can modify logs. I have not get much helps from google. As per log4j2 documents Rewrite is an interface has rewrite method and MapRewritePolicy is implementation class, when I run this I am able to see my web3.log file generating but not seeing any modification in log content. I seen MapRewritePolicy source code and created local implementation class as MapRewritePolicyImpl.java in my project and put some System.out to see code flow is coming into this class from log4j2.xml file. I have modified my log4j2.xml to use MapRewritePolicyImpl.java but code flow is not going into my MapRewritePolicyImpl.java class.

<Rewrite name="rewrite" >
            <Appender-Ref ref="web3" />
             <MapRewritePolicyImpl">
                <KeyValuePair key="creditCard" value="new12345"/>
            </MapRewritePolicyImpl> 
        </Rewrite>



    <Configuration monitorInterval="5" status="debug" strict="true">
        <Appenders>
            <RollingFile name="web3" fileName="../logs/web3.log" 
                filePattern="${sys:catalina.home}/logs/$${date:yyyy-MM-dd}/web3-%d{yyyy-MM-dd}-%i.log.gz">
                <PatternLayout
                    pattern="%d{dd/MM/yyyy HH:mm:ss,SSS} [%X{cartID}] [%X{sessionId}] [%p] [%t] [%c] (%F:%L)  - %m%n" />
                <Policies>
                    <TimeBasedTriggeringPolicy interval="1"
                        modulate="true" />
                    <SizeBasedTriggeringPolicy size="10 MB" />

                </Policies>
            </RollingFile>
            <Rewrite name="rewrite" >
                <Appender-Ref ref="web3" />
                 <MapRewritePolicy">
                    <KeyValuePair key="creditCard" value="new12345"/>
                </MapRewritePolicy> 
            </Rewrite>
    </Appenders>
    <Loggers>
        <Logger name="com.virginamerica" level="info" additivity="false">
            <!-- <Appender-Ref ref="web3" /> -->
            <Appender-Ref ref="rewrite"/>
        </Logger>
    </Loggers>
</Configuration>

Solution

MapRewritePolicy will evaluate LogEvents that contain a MapMessage and will add or update elements of the Map. This only works if your application calls logger.info(new MapMessage(keyValueMap)). I suspect that this is not what your application is currently doing.

Usually, your messages will be either a SimpleMessage (if you called logger.info("Just a string without parameters")) or a ParameterizedMessage (if you called logger.info("Hi {}!", name)). RewriteAppender will not be able to do anything with either SimpleMessage or ParameterizedMessages, so nothing is replaced...

You may want to take a look at the documentation for PatternLayout: this has the capability to replace regular expressions in string messages with some replacement value, if you use the replace{pattern}{regex}{substitution} pattern.