Using WSRP 2.0 with JSR 168 and 286 Portlets

Introducing Wsrp Specifications

The WSRP specification (WSRP specification version 1 introduced two complimentary the concepts of Producer and Consumer. The WSRP 1.0 (WSRP specification version 1 specification requires that every producer implements two required interfaces, and allows optional implementation of two others:

• 1.

  Service Description Interface (required): This interface allows a WSRP producer to advertise services and its capabilities to consumers. A WSRP consumer can use this interface to query a producer to discover what user-facing services the producer offers. Furthermore, the description also contains additional metadata and technical capabilities of the producer. The producer's metadata might include information about whether the producer requires registration or cookie initialization before a consumer can interact with any of the remote portlets. For the consumer, this interface can be used as a discovery means to determine and localize the set of offered remote portlets.

• 2.

  Markup Interface (required): This interface allows a consumer to interact with a remotely running portlet supplied by the producer. For example, a consumer would use this interface to perform some interaction when an end-user submits a form from the portal page. Since this interface supports the notion of the state, the portal might obtain the latest markup based on the current state of the portlet (for example when the user clicks refresh button or interaction with another portlet on the same page takes place).

• 3.

  Registration Interface (optional): This interface serves as a mechanism for opening a dialogue between the producer and consumer so that they can exchange information about each others' technical capabilities. The registration interface allows a producer to ask consumers to provide additional information before they start interaction with the service through the service description interface and markup interfaces. This mechanism enables a producer to customize its interaction with a specific type of consumer. For example, a producer may use a filter and reduce the number of offered portlets for a particular consumer.

• 4.

  Portlet Management Interface (optional): This interface gives the consumer control over the life cycle methods of the remote portlet. A consumer acquires the ability to customize a portlet’s behaviour, or destroy an instance of a remote portlet using this interface.

Processing user interaction When the user clicks on a link or submits form data, the consumer application controls the processing and invokes the performInteraction() method (). When the producer receives this call, it processes the action and returns the updated state. To redraw the complete page, the consumer then invokes the getMarkup() call to receive the latest markup fragment. Because the state of the producer has changed since the previous getMarkup() call, the markup fragment returned is typically different from the one previously returned. The end user can then perform another action, which starts a new interaction cycle. (See Figure 1)

Figure 1.

Remote portlet interaction in view and action modes

Handling customization and initialization: In a typical interaction a single centrally hosted services are used by multiple consumer applications and/or multiple individual users. The WSRP protocol supports multiple configurations of a single service. Good example is a lookup in a remote list of the course offerings and subjects offered within a particular course to international students. The list can be configured to display different offerings per semester, different currencies for subject fees or both depending on the consumer country and language prerequisites.