Is exception handling mandatory in MDC.remove() or MDC.put()?

Question

import org.slf4j.MDC;

            MDC.put(ID1, id1);
        MDC.put(ID2, id2);
        MDC.put(ID3, id3);
        try {
              return joinPoint.proceed();
        } finally {
            MDC.remove(ID1);
            MDC.remove(ID2);
            MDC.remove(ID3);
        }

• Assuming there is a code as above, Exceptions can also occur for remove, put()
• If an exception occurs in the deletion process for id1, you cannot delete irrelevant id2,id3. To prevent this problem, do I have to take an additional process of taking and processing an exception for that part of the above code? Like the attached code The code below is only processed for ID1, but you need a try-catch statement every time you add it

        MDC.put(ID1, id1);
        MDC.put(ID2, id2);
        MDC.put(ID3, id3);
        try {
              return joinPoint.proceed();
        } finally {
                try{
                     MDC.remove(ID1); 
                } finally {
                           MDC.remove(ID2);
                   MDC.remove(ID3);
                }
           
          
        }

• There's no compiler exception

---

If there's anything lacking in the question, please point it out. I'll reflect it and upload it again

Answer 1

I assume that you are actually asking about the correct way to do the removals.

If we assume that any of the put or remove calls can throw an exception, AND that not tidying up the MDC is unacceptable, then the correct way to write this would be:

try {
    MDC.put(ID1, id1);
    try {
        MDC.put(ID2, id2);
        try {
            MDC.put(ID3, id3);
            return joinPoint.proceed();
        } finally {
            MDC.remove(ID3);
        }
    } finally {
        MDC.remove(ID2);
    }
} finally {
    MDC.remove(ID1);
}

You can simplify this by using putCloseable instead of put as follows:

try (
    MDC.MDCCloseable c1 = MDC.putCloseable(ID1, id1);
    MDC.MDCCloseable c2 = MDC.putCloseable(ID2, id2);
    MDC.MDCCloseable c3 = MDC.putCloseable(ID3, id2);
) {
    return joinPoint.proceed();
}

The putCloseable variant returns an adapter that implements Closeable where the close() method performs the required remove.

On the other hand, if we treat the MDC javadocs as defining the behavior, then the only case where remove is documented to throw an exception is when the key is null. You should be able to guarantee that ID1, ID2 and ID3 are not null. If you can, the above code is unnecessary; i.e. your original version with a single finally should be fine.