Portals

The IT industry has seen various milestones. Some of the major milestones are the introduction of Desktop PCs, Windows platform, C language, the evolution of OOPS and C++, Internet technologies, and JAVA. WSRP has all of the necessary characteristics for becoming a member of this elite group. WSRP is an example of real-time integration and it exploits the power of Web services and portlet technologies.

WSRP stands for Web Services for Remote Portlets. It is an OASIS standard and a dynamic plug-in for portal pages. This allows portal or application owners to easily integrate remotely available third-party portlets or their own portlets using Web services. WSRP provides the dynamic integration in portals and integrated portlets are dynamically updated from the provider's own servers.

Let's understand a few related terms before looking at the inside story of WSRP.

Web Services - Web services provide an application integration technology that can be successfully used over the Internet, which allows business applications to communicate and cooperate over the Internet. Web services allow objects to be distributed across Web sites where clients communicate and cooperate over the Internet. Registry standards enhance this by defining how the Web services may be published, found, and bound with minimal human interaction. Web Services standards are as follows.

SOAP - A standard for messaging over HTTP and other Internet protocols. This is a universal service access protocol. Technical features include:

• Structured envelope for XML messages
• Headers…message path
• Protocol independent, i.e., can work with a variety of lower protocols like HTTP, HTPS, SMTP, and RPC
• Data model and encodings

WSDL - A language for describing the programmatic interfaces of Web services. This is an XML document that describes the properties (interfaces) of the service. The language does the following:

• Provides the common interface definition language
• Follows XML vocabulary and structure
• Provides operational information about service, interface, implementation details, access protocol, contact endpoints, and security

XML - Solves a key technology requirement that appears in many places. By offering a standard, flexible, and inherently extensible data format, XML significantly reduces the burden of deploying the many technologies needed for Web services. WSDL is one of them.

UDDI/ebXML - A look-up business registry or database standard for indexing and publishing Web services so that clients (applications and development tools) can locate their descriptions. Typically it uses SOAP messaging (usually XML/HTTP) for publishing, editing, browsing, and searching for information in a registry. Some of the features are given below:

• Share information
• Discover other participants' services
• Define how you can interact across the Internet

ebXML is a suite of XML specification- related processes and behavior designed to provide an e-infrastructure for B2B collaboration and integration. SOAP provides a low-level foundation that we can use to build these extended business exchanges, such as where there is a need for an agreed-upon structure for business transactions, multirequest transactions, schemas, and document flow - wherever SOAP provides some limitations. For more info on ebXML visit www.ebxml.org.

Basically, a Web service's sequence of flow for engaging (see Figure 1) is:

1. A Service provider implements a Web service and describes its interfaces using WSDL. Further, the Web service is published with central Service Registry.
2. A service requestor looks up for the Web services from a centralized Service registry using WDSL.
3. A service requestor binds to a specific service provider for a Web service using a WSDL file.
4. A service requestor creates a service proxy (WSDL).
5. A service requestor now communicates with the server (service provider) using SOAP (i.e., invokes the service via SOAP and receives a response via SOAP).

For more information visit http://developers.sun.com/techtopics/webservices/essentials.html.

Portal
A portal is a Web-based application that commonly provides personalization, single sign on, and content aggregation from different sources for providing useful information to users. Portals uses both "push" and "pull" technologies to transmit information to users through a standardized Web-based interface, and they can be classified as vertical portals, horizontal portals, or corporate or enterprise (intranet) portals. Typically, portals get information from local or remote data sources, for example, from databases, directory services, transaction systems, syndicated content providers, and remote Web sites, etc. A portal is an application that aggregates portlet applications together in a presentable format. They render and aggregate this information into composite pages to provide information to users in a compact and easily consumed form.

Portlet
A portlet is a Java technology-based Web component that is managed by a portlet container that processes requests and generates dynamic content called fragments. The portlet is essentially a small reusable application and it runs under the portlet container. The portlet container provides the runtime environment required for the execution of portlets; it manages the life cycle of portlets and provides a persistent storage mechanism for portlet preferences. Portlet technology is similar to Servlet/JSP, which is managed by servlet container. A fragment is a piece of markup (e.g., HTML, XHTML, WML) that adheres to certain rules. Fragments can be aggregated with other fragments to form a complete document. The portlet is accessible to users via a portal interface and portal uses them as pluggable user interface components that provide a presentation layer to information systems.

A portlet looks like a small window application within a portal page (see Figure 2). Portlets support some modes such as:

• View Mode - This mode provides the portlets with their actual functionality
• Edit Mode - In this mode we can edit the portlet's instance data
• Help Mode - Explains how the portlet should be used
• Design Mode - Used for changing the appearance of the portlet
• Preview Mode - Used for previewing the portlet's appearance

Portals also support window states like Minimized, Normal, and Maximized to display portlets in different sizes (www.jcp.org/aboutJava/communityprocess/final/jsr168/).

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