How to create custom RewritePolicy in log4j2? -

i'm trying code own rewritepolicy in log4j2. documentation states :

rewritepolicy interface allows implementations inspect , possibly modify logevents before passed appender. rewritepolicy declares single method named rewrite must implemented. method passed logevent , can return same event or create new one.

here's java class :

public final class markerinjectorrewritepolicy implements rewritepolicy {      @override     public logevent rewrite(final logevent event) {         final marker marker = event.getmarker();         if (marker == null)             return event;          // if there's marker, add threadcontextmap routingappender can routes log messages         event.getcontextmap().put("_marker", marker.getname());         return event;     } } 

here's yaml configuration file :

rewrite:   name: rewrite_appender   appenderref:     ref: routing_appender   propertiesrewritepolicy:     property:       - name: foo         value: bar 

however have no idea how inject in configuration file. how can make work @ runtime?

your custom rewrite policy should coded log4j2 plugin. enables configure custom rewritepolicy in rewriteappender.

@plugin(name = "injectmarkerpolicy", category = "core",         elementtype = "rewritepolicy", printobject = true) public final class markerinjectorrewritepolicy implements rewritepolicy {      @override     public logevent rewrite(final logevent event) {         final marker marker = event.getmarker();         if (marker == null)             return event;          // if there's marker, add threadcontextmap         // routingappender can routes log messages          // event's context map immutable, need make copy...         map<string, string> mdc = new hashmap<>(event.getcontextmap());         mdc.put("_marker", marker.getname());          logevent result = new log4jlogevent(event.getloggername(), event.getmarker(),             event.getloggerfqcn(), event.getlevel(), event.getmessage(),             event.getthrown(), mdc, event.getcontextstack(),             event.getthreadname(), event.getsource(), event.gettimemillis());          return result;     } } 

example config (todo: set correct value packages attribute):

<configuration status="trace" packages="my.rewritepolicy.plugin.package">   <appenders>     <console name="stdout">       <patternlayout pattern="[%-5level] %c{1.} %m%n"/>     </console>     <rewrite name="rewrite">       <injectmarkerpolicy />       <appenderref ref="stdout"/>     </rewrite>   </appenders>   <loggers>     <root level="trace">       <appenderref ref="rewrite"/>     </root>   </loggers> </configuration>