I am trying to query coherence and get the data in to my client. I am using Jconsole to monitor coherence. Is there a way I can find the average size of the object stored in the cache in bytes, so that I can determine how many bytes are sent over the network from coherence back to my client?
If you are using binary unit calculator, you can get object size information from MBean.
You should check cache MBean on back tier. "Size" attribute is number of entries in this instance of backing map and "Units" attribute would be size in bytes (but only if binary unit calculator is configured).
Alternatively, if you interested in traffic, you could check extend proxy service MBean in "ConnectionManager" group. It has "TotalBytesSent" and "TotalBytesReceived" attributes.