Chapter 21. Integrating External Web Services with the JBoss Enterprise SOA Platform

A web service is a way of making two applications communicate over the web. A web service consists of a set of tools to achieve this aim. There are two types of web service: REST-compliant ones, (the purpose of which is to manipulate XML representations of web resources) and arbitrary Web services (through which the service can expose any operation).

A web service end-point is software that implements a web service. They are used to implement message-based communication between web services in a service-oriented architectural environment.

The external applications to which these registry entries point can include .NET programs, other external Java-based application servers and LAMP software bundles.

The Web Services Description Language (WSDL) is an XML-based language that is used to define Web service interfaces. An application that consumes a Web service parses the service’s WSDL document to discover the:

For each operation, the WSDL describes the interface format to which the client must adhere.

REST (Representational State Transfer) is a type of software architecture, consisting of clients and servers. It was designed specifically for distributed networks, including the internet. Central to this is the idea of multiple resources (data sources), each of which is identified by a unique, global address. In order to manipulate these resources,the clients and servers communicate via a standardized interface and exchange data.

The SOAPProcessor is an action that allows you to invoke a JBossWS-hosted web service end-point through any JBossESB-hosted listener. Via this action, the enterprise service bus can expose web service end-points for services that do not already expose them. You can then invoke services over any transport channel supported by the enterprise service bus, such as HTTP, FTP or JMS.

The SOAPProcessor supports both the JBossWS-Native and JBossWS-CXF stacks.

The SOAPProxy is an action that "consumes" external web service end-points. It also allows you to re-publish a web service end-point via the Enterprise Service Bus. Sitting between the external services and the ESB, the purpose of this intermediary is to provide an abstraction layer it provides the following functionality:

The JBoss Enterprise SOA Platform's enterprise service bus sits between the producer of the resource and the client application that ultimately consumes it. The ESB's purpose is to provide an abstraction layer, thereby giving these advantages:

Content-based routers send messages that do not have destination addresses to their correct end-points. Content-based routing works by applying a set of rules (which can be defined within XPath or Drools notation) to the body of the message. These rules ascertain which parties are interested in the message. This means the sending application does not have to supply a destination address.

A typical use case is to serve priority messages in a high priority queue. The advantage here is that the routing rules can be changed on-the-fly while the service runs if it is configured in that way. (However, this has significant performance drawbacks.)

Other situations in which a content-based router might be useful include when the original destination no longer exists, the service has moved or the application simply wants to have more control over where messages go based on its content of factors such as the time of day.

A static-based router helps to coordinate information across your network. It transfers information between servers and tells them where to send their messages. You can program it to take certain routes if you feel the default is inefficient. You can only use it to route to other services.

A routing key is used to match messages and the items to which they are bound. In the context of the JBoss Enterprise SOA Platform, the routing key can be applied to a message which will then be sent to a queue which has been given the same routing key.