Originally posted by Chetan Sahasrabudhe:
No so convincing response.
Any technical need or something based on scalability of J2EE thing
Manikandan is right that the way it is now is more "normalized." My original response was mostly to this effect, stating a servlet can have multiple mappings creating one-to-many relationships. I removed that and shortened my response because the way I worded my explanation didn't sound very friendly.
Manikandan very well might also be correct that the sole motivation for the separation was to keep the roles of deployer and developer separate. This role separation in deployment descriptors is made much more obvious for EJBs (SCBCD) but that's mainly because EJBs were intended to be used as reusable, pluggable components that could be deployed in multiple ways.
But to explain my earlier point: it is also easier the way it currently stands. For example, it is possible for a requested URL to match more than one mapping. Which one mapping then will pick up the request? It's easier for the developer (or whoever) to determine which mapping gets the request with all the mappings together.