Building Web Services with JAX-RPC - The J2EE 1.4 Tutorial

Building Web Services with JAX-RPC

JAX-RPC stands for Java API for XML-based RPC. JAX-RPC is a technology for building web services and clients that use remote procedure calls (RPC) and XML. Often used in a distributed client-server model, an RPC mechanism enables clients to execute procedures on other systems.

In JAX-RPC, a remote procedure call is represented by an XML-based protocol such as SOAP. The SOAP specification defines the envelope structure, encoding rules, and conventions for representing remote procedure calls and responses. These calls and responses are transmitted as SOAP messages (XML files) over HTTP.

Although SOAP messages are complex, the JAX-RPC API hides this complexity from the application developer. On the server side, the developer specifies the remote procedures by defining methods in an interface written in the Java programming language. The developer also codes one or more classes that implement those methods. Client programs are also easy to code. A client creates a proxy (a local object representing the service) and then simply invokes methods on the proxy. With JAX-RPC, the developer does not generate or parse SOAP messages. It is the JAX-RPC runtime system that converts the API calls and responses to and from SOAP messages.

With JAX-RPC, clients and web services have a big advantage: the platform independence of the Java programming language. In addition, JAX-RPC is not restrictive: a JAX-RPC client can access a web service that is not running on the Java platform, and vice versa. This flexibility is possible because JAX-RPC uses technologies defined by the World Wide Web Consortium (W3C): HTTP, SOAP, and the Web Service Description Language (WSDL). WSDL specifies an XML format for describing a service as a set of endpoints operating on messages.