Your question seems to indicate that you are not very familiar with the way SNMP supervision works. Let me try to straighten it out. Chapter 2.1 of RFC 1905 provides a more formal definition of the terms I'll use:
http://www.ietf.org/rfc/rfc1905.txt
SNMP4j is a library which allows you to more easily write SNMP applications in Java. An SNMP application is either a Manager, which supervises an Agent, or it can be an Agent. It sounds like you are looking to implement an SNMP Manager.
Before you can use an SNMP Manager to monitor your Spring application, or the machine on which it is running, an SNMP Agent must be installed on the machine. Whether or not this is the case is not evident from your question, but a quick google search indicates that the "SNMP for Spring" application may be used as such an Agent. You can check the "Getting Started" page here for a quick start.
http://spring-snmp.sourceforge.net/
Now, once you have an Agent, how to supervise it is more of an open question.
You could get right to work at implementing your own SNMP Manager, and SNMP4j might well be the right tool for the job if you're a Java programmer. However, I would really advise against diving right into that problem. If your organization needs to supervise services on a network, look into the multitude of commercial and free network management tools that are available. I believe that the Open Source systems Nagios, ZenOSS and OpenNMS all provide SNMP monitoring capabilities in their free implementations.
If you implement your own threshold-based bandwidth monitoring system, you might later be tempted to expand it to handle more than just your Spring system, and add trap reception, and .... and in the end you will have reinvented (most of) the figurative wheel (by which I mean an NMS system) which might not do the job quite as well as one of the aforementioned products.