RMH book probably is the best book on J2EE web services but not a must have for the certification exam. Yes you can use the JAX-RPC specifications to study for objective 4. You also need Servlet 2.4 and EJB 2.1 specifications to understand how they can be used as service end points and/or service clients. You also need web services blue prints (you need this one even if you have RMH book) to understand how you might design an end point given transaction, security etc. requirements.
objective 4 = JAX-RPC 1.1, EJB 2.1, Servlet 2.4 (little bit) and Web Services blue prints.
Wait for a while (while I go home and get the filw) and I will post the mapping between study objectives (only objective 4) and sections in the specs to read.
Woops!!! Totally forgot to post mappings. Here it goes. Feel free to challenge it and suggest changes.
4.1 Explain the service description model, client connection types, interaction modes, transport mechanisms/protocols, and endpoint types as they relate to JAX-RPC. MAPPING: JAX-RPC 1.1 spec 2.1, 3-R01 through R09
4.2 Given a set of requirements for a web service, such as transactional needs, and security requirements, design and develop web service applications that use JAX-RPC servlet endpoints and stateless session bean endpoints. MAPPING: EJB 2.1 spec 7.5.3, 7.11.9, 7.12.2, 7.12.7, 18.3.2, 220.127.116.11 Servlet 2.4 spec 13.1.1, 13.4-23 JAX-RPC 1.1 spec 2.2, chapter 10, 13
4.3 Given a set of requirements, design and develop a web sevice client, such as a J2EE client and a stand-alone Java client, using the appropriate JAX-RPC client connection style. MAPPING: EJB 2.1 spec 6.11, 5.5, 20.4 JAX-RPC 1.1 spec 9.2, 9.3 WSBluePrint 4.3, 4.4, 4.6
4.4 Given a set of requirements, develop and configure a web service client that accesses a stateful web service. MAPPING: WSBluePrint 4.7.1
4.5 Explain the advantages and disadvantages of a WSDL to Java vs. a Java to WSDL development approach. MAPPING: WSBluePrint 3.4.1
4.6 Describe the advantages and disadvantages of web service applications that use either synchronous/request response, one-way RPC, or non-blocking RPC invocation modes. MAPPING: I DO NOT KNOW
4.7 Use the JAX-RPC Handler API to create a SOAP message handler, describe the function of a handler chain, and describe the role of SAAJ when creating a message handler. MAPPING: JAX-RPC 1.1 spec chapter 12 (at least section 12.1)
Hope this helps. I will work on other objectives eventually. I will post more info as I prepare it.