I am not clear about the JavaWeb services space.There seem to be many APIs(JWSDP,Spring etc) and many ways of creating web services in Java.Which is the most commonly used API that will help me develop web services that can be deployed on various application servers.Also is Spring a good option for this?Please advise.
The most commonly used APIs are JAX-WS (for SOAP-based WS) and JAX-RS (for RESTful WS). JAX-WS is implemented by several toolkits like Apache Axis2 and Metro (on dev.java.net), while the most common JAX-RS implementation is Sun's reference implementation called Jersey (also on dev.java.net).
JWSDP is obsolete; don't use it for anything.
Not sure what Spring offers; check for its JAX-WS and JAX-RS support.