Log4j (SLF4J) MDC Context in Struts 2 Interceptor

I find that one can set the Log4j (SL4J) MDC context in a thread safe way in a general filter (Code from Adding user info to log entries in a multi-user app using Mapped Diagnostic Context)

import org.slf4j.MDC;
import javax.servlet.*;
import java.io.IOException;
 
public class MDCFilter implements Filter {
 
  @Override
  public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain)
          throws IOException, ServletException {
      User user= (User) session.getAttribute("USerSession");
      MDC.put("userName", user.getUserName() );
    try {
      chain.doFilter(req, resp);
    } finally {
        MDC.remove("userName");
    }
  }
 
}

Can I do the same approach in the Struts 2 interceptor ?! What I wonder is thread safty issues.

Struts 2 interceptor and servlet filters are not both thread safe and MDC implementation is thread safe, so if above code works fine in a filter, theoretically it must be work thread safe in the interceptor.

Any comments ?!

Interceptors are not thread safe means that you have to write them in thread safe manner. For example below interceptor is thread safe.

public class LoggerInterceptor extends AbstractInterceptor {
  @Override
  public String intercept(ActionInvocation invocation) throws Exception {
    HttpSession session = ServletActionContext.getRequest().getSession();
    User user= (User) session.getAttribute("USerSession");
    MDC.put("userName", user.getUserName() );
    String result;
    try {
      result = invocation.invoke();
    } finally {
      MDC.remove("userName");
    }
    return result;
  }
}