Delayed Server Request Response Logger.java

/**
 * This class delays the logging of request and response events.

 * @implNote This class uses a thread local to cache request serialization in the form of a builder
 * If the response received from service passes the supplied predicate, then both request and response
 * will be logged or else nothing will be logged.
*/
public class DelayedRequestResponseLoggingFilter implements ContainerRequestFilter, ContainerResponseFilter, WriterInterceptor {
    
    private final ResponseCondition responseCondition;
    private final ThreadLocal<StringBuilder> requestLogCache = new ThreadLocal<>();

    @Override
    public void filter(ContainerRequestContext requestContext) throws IOException {
        StringBuilder requestLog = requestResponseBuilder.buildRequestLog(requestContext);
        //instead of logging here directly, cache the result in the thread local.
        requestLogCache.set(requestLog);
    }

    @Override
    public void filter(ContainerRequestContext requestContext, ContainerResponseContext responseContext) {
        try {
            int status = responseContext.getStatus();
            if (responseCondition.test(status)) {
                //response matches the user defined predicate..log both requests and responses
                String requestLog = requestLogCache.get();
                log(requestLog);
                
                String responseLog = requestResponseBuilder.buildResponseLog(requestContext, responseContext);                    
                log(responseLog);                                  
            }
        } finally {
            requestLogCache.remove();
        }
    }
}