I forgot to mention that i tried to remove the spring jars from my war, and yet i get another error:
Caused by: java.lang.RuntimeException: Invalid schema document passed to AbstractDataBinding.addSchemaDocument, not in W3C schema namespace
Found the answer. When copying the spring jars into common/lib, we have to delete all the relative to spring jars, from our war package. Again, class loading issue.
When facing a similar problem, don't do the same mistake with me. That is, don't ask questions to the community, try to address the class loading problem first.