creating an appender with below java code programmatically ,I need to add MDC with my partternLayout

Question

Creating an appender programmatically in java with log4j2.xml need to add MDC key variable with PatternLayout of Log4j2 , can any one look into below code and tell how to add mdc variable whose value will be replaced brfore the looger.info call

PatternLayout layout = PatternLayout.newBuilder().withConfiguration(config)
            .withPattern("%d{HH:mm:ss.SSS} %level %msg%n").build();


final Appender appender = FileAppender.createAppender("target/test.log", "false", "false", "File", "true",
              "false", "false", "4000", layout, null, "false", null, config);
   appender.start();
   addAppender(appender);
   LoggerConfig loggerConfig = LoggerConfig.createLogger("false", "info", "org.apache.logging.log4j",
              "true", refs, null, config, null );
   loggerConfig.addAppender(appender, null, null);
   addLogger("com", loggerConfig);

Now I need that whenever my log statements are printed they also print some value telling their state.

How can I add MDC key while creating above pattern layout ?

current behaviour of ==> logger.info(" Here we are "); is printing " Here we are "

My expectation is => statement should come with MDC key .

Answer 1

Your pattern should contain something like %X{someKey} .

Then in your code, you would set the value, e.g :

MDC.put("someKey", someValue);