Managing state in SOA

A good link on managing state in SOA. Some of the key points:
1. To Manage conversation state, a state identifier needs to maintain following information w.r.t each request-response interaction

1. Unique identifier of the Web service client


2. Identifier of the Web service conversation originated for that client


3. Identifier of the service request within that conversation


4. Indicator of the conversation phase between the service requester (client) and service provider (Starting, Continuing, and Ending), which is used by the service for proper state maintenance


5. Indicator of the interaction status between the service distribution function of the Web services infrastructure and the invocation interface (very helpful in dynamic invocations with late-binding of Web service interfaces)

2. This identifier information can be passed in three ways:
* Pass the identifier information as an extra parameter in the Web service method; the Web service interface can be designed to accept not only the XML document message, but also to accept additional parameters that represent the state identifier information.
* Pass the identifier information as a part of the XML document—the XML document can contain such information embedded within its body.
* Pass the identifier information in the SOAP message header.
3. First two methods are not preferred as code becomes harder to maintain.
4. Three-step development process:
1. Design and code the basic service components.
2. Develop SOAP message handlers.
3. Construct Web services (expose) out of developed J2EE components.
5. SOAP handlers are for: to handle the insertion of state qualifiers into the standard SOAP message definition. In JAX-RPC services, a handler is represented by a handler class that implements handleRequest() and handleResponse() methods for modifying the request and response message.
6. Create Handlers implementing javax.xml.rpc.handler.Handler and implementing the handleRequest method. The javax.xml.soap.SOAPMessage class is used by the handler to manipulate the SOAP message. A SOAPMessage object contains a SOAPPart object that contains the actual SOAP XML document and a SOAPEnvelope object that is "decomposed" to access SOAP body and header.
7. Get a SoapFactory instance and createElement using it. To the element addTextNode. Finally construct WS using handlers and deploy to AS.