Run a Runnable when a specific Log4J message is appended to the log

Log4JHook.java

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.core.Appender;
import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.appender.AbstractAppender;
import org.apache.logging.log4j.core.layout.PatternLayout;

import java.lang.reflect.InvocationTargetException;
import java.util.function.Predicate;

/**
 * Executes the passed Runnable when a matching log message is appended
 */
public class LogHook extends AbstractAppender {

    private final Predicate<LogEvent> predicate;
    private final Runnable runnable;

    public LogHook(String message, Runnable runnable) {
        this(event -> event.getMessage().getFormattedMessage().equals(message), runnable);
    }
    public LogHook(String logger, String message, Runnable runnable) {
        this(event -> (event.getLoggerName().equals(logger) || event.getSource().getClassName().equals(logger)) && event.getMessage().getFormattedMessage().equals(message), runnable);
    }
    public LogHook(Predicate<LogEvent> predicate, Runnable runnable) {
        super("LogHook", null, PatternLayout.createDefaultLayout(), false);
        this.predicate = predicate;
        this.runnable = runnable;

        Logger rootLogger = LogManager.getRootLogger();
        try {
            rootLogger.getClass().getMethod("addAppender", Appender.class).invoke(rootLogger, this);
        } catch (IllegalAccessException | InvocationTargetException | NoSuchMethodException e) {
            throw new RuntimeException(e);
        }
    }

    @Override
    public void append(LogEvent event) {
        if (predicate.test(event)) {
            try {
                Thread thread = new Thread(runnable);
                thread.start();
                thread.join();
            } catch (InterruptedException e) {
                throw new RuntimeException(e);
            }
        }
    }

    @Override
    public boolean isStarted() {
        return true;
    }

}