thread-safe

thread-safe

Identify which attribute scopes are thread-safe:

1. Local variables Yes, thread-safe
2. Instance variables
Not thread-safe
Since a single servlet instance may be handling multiple service requests at any given time.
3. Class variables
Not thread-safe
Since multiple servlets and /or service requests may try to access a class variable concurrently.
4. Request attributes
Yes, thread-safe
Since the request object is a local variable
5. Session attributes
Not thread-safe
Since sessions are scoped at the web application level, hence the same session object can be accessed concurrently by multiple servlets and their service requests
6. Context attributes
Not thread-safe
Since the same context object can be accessed concurrently by multiple servlets and their service requests