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Enterprise Portal Integration and The Enterprise Service Bus

Enterprise Portal Integration and The Enterprise Service Bus

The high interest in business visibility, flexibility, and knowledge management has made portal technology a popular choice for monitoring, searching, and managing business activity across the enterprise. BEA WebLogic Platform provides an attractive platform for building highly dynamic enterprise portals that can aggregate, organize, and present information from multiple back-end systems. Whether the portal is implemented with the feature-rich environment of WebLogic Portal Server, or through an MVC framework such as "Jakarta Struts", the newest release of BEA's 8.1 platform provides many new features that create a powerful portal environment.

However, as enterprise portals begin to aggregate ever-increasing numbers of services across disparate technology domains, geographic boundaries, and even organizational boundaries, portal architects will need to find ways to manage the complexity of the environment. Clearly, building "one-off", reliable, point-to-point integrations between the portal and each service does not scale from a development, deployment, or runtime perspective. There is a need for the concept of a "services network," providing reliable transport, intelligent routing, advanced services management features, and the ability to operate in a highly distributed and federated environment.

Fortunately, a new type of infrastructure known as the enterprise service bus (ESB; see sidebar "The ESB: Your Web Services Network") provides the level of sophistication required for even the most demanding of portal environments. An ESB is a standards-based, service-oriented backbone capable of reliably connecting and coordinating hundreds of application endpoints.

ESBs provide the ideal architecture for enterprises needing to connect a variety of heterogeneous systems distributed across disparate data centers, while still maintaining absolute transactional integrity. Furthermore, it provides several advanced services that are primarily configured through deployment time constructs, shielding portal applications from constantly needing to be revised and redeployed to manage changes on the back end.

Even if you are planning to deploy a portal to integrate systems within a homogenous environment with a handful of back-end services, there are still significant advantages in incorporating an ESB as the integration network. A comprehensive ESB vendor will provide out-of-the-box management, security, reliability, high performing service requests, native XML processing, complex routing, and transformations as value-added features in the bus. Furthermore, as a standards-based implementation of service-oriented architecture (SOA), an ESB provides the necessary abstraction layer to fulfill the full promises of SOA. The ESB provides the ability to seamlessly relocate the underlying service implementation to another technology, geographic, or organizational domain, without sacrificing the traditional values of homogenous environments: management, security, reliability, scalability, and performance.

In this article, we'll examine two key use cases that demonstrate the power and flexibility of the ESB in integrating highly distributed services with portals and Web applications using BEA WebLogic Platform 8.1. In the next part in this two-part series, we will show you how the ESB can provide additional value to the organization through operational awareness, business activity monitoring (BAM), and service-oriented business process management, allowing the portal to fully harness the full value of the services within the extended enterprise.

Avitek Medical Records: Expanding Its Business Model
The WebLogic 8.1 Platform ships a comprehensive J2EE tutorial known as "Avitek Medical Records," designed to demonstrate all of the core features of the J2EE platform. The tutorial is modeled around the idea of a portal (a J2EE Struts application) that provides the ability for patients, physicians, and administrators to view an aggregated set of medical records. In addition, the application demonstrates the ability to link with external clients through Web services interfaces, providing the ability to interact with the Avitek services without going through the presentation tier.

As a premise for this article, we are going to assume that "business is booming" at Avitek and they have acquired three new sources of medical records to integrate into the portal. To complicate matters, the new sources are geographically distributed across suspect networks, and contain a mixture of technology environments (a variety of J2EE application server vendors, Microsoft .NET, and custom solutions). In fact, Avitek would like an architecture that accommodates change, as they will most likely be acquiring new sources of information incrementally, and migrating the sources to the latest and greatest technologies slowly over time.

Although the architecture for Avitek Medical Records advertises the ability to integrate new sources of medical records using HTTP/Web services, this article will demonstrate some key use cases that indicate that a pure-play Web services environment is not enough. There are issues related to reliability, performance, richness of communications models (request/response, unidirectional, asynchronous services, etc.), quality of service, performance, management, and security that call into question the viability of a pure HTTP/Web services approach. For this reason, we recommend that Avitek modify its architecture to incorporate the notion of an ESB (see Figure 1).

The ESB, based on industry-standard JMS, would provide the enterprise-grade backbone to reliably link services together into a cohesive operating unit, capable of servicing the full range of integration scenarios required by most portals. This article will cover a couple of the many scenarios available once the ESB is put in place:
1.  Forward Cache: The ability to move data from distributed systems close to the presentation tier for low-latency, read-only access to the data
2.  Federated Query: The ability to efficiently query multiple systems and aggregate the responses asynchronously at the presentation tier

Forward Service Cache
The "Forward Cache Service" use case addresses the problem of needing to expose data from a back-office system to the presentation tier. Although the presentation tier could easily interact with the back-office system through a request/response paradigm, there are several reasons why this could be impractical:
1.  The back-office system is incapable of sustaining the load required to support the front-end presentation tier.
2.  The latency for request/response would exceed the tolerances of the presentation tier.
3.  There would be risk associated with exposing the back-office system directly to the presentation tier - stability, or impacts on existing service levels.
4.  The back-office system could be in a different geography than the presentation tier; if links go down between the two data centers, the data should still be available to end users.

The ESB can be used to reliably forward changes to a cache in the presentation tier. The key word here is "reliably." In a distributed, SOA-based environment, careful attention must be paid to how systems interoperate, and what would happen in the event of failures or downtime. In many situations, systems are not capable of providing the necessary message resend and "in-doubt resolution" required for this type of reliability. An ESB can offload this complexity from the systems (see Figure 2).

The ESB, by its definition, is a distributed services network capable of reliable communications between any two entities. The deployment options provided by ESB providers will allow the quality of service to be tuned to the exact needs of the application. Based on industry-standard JMS, the two entities communicate reliably using standard interfaces; the ESB handles the complexity of routing and guaranteeing the delivery of the change notification.

Fortunately, the Avitek demo would not need to change drastically to take advantage of the ESB. Given the ESB's standards-based approach, the ESB provider hooks in through the JMS interface. Avitek's demo includes an MDB listening on a JMS connection to "upload" XML records into the MedRec database. Once the records are loaded into the database, they are available to the front-end portal using standard techniques to query the database. Of course, the pattern could also be enhanced to accommodate record deletion requests, or even partial record updates (see Figure 3).

But how does this differ from standard JMS providers? JMS providers provide asynchronous, guaranteed messaging capability in a single domain. Attempting to link multiple JMS messaging domains typically requires some type of custom bridge to forward messages reliably between multiple domains. However, ESB providers provide native, end-to-end JMS communications in a distributed and federated environment, obviating the need for custom bridges. Furthermore, the ESB provides additional standards-based connectivity, such as Web services and JCA adapters (see sidebar, "ESB Providers: Value-Added Services"), allowing the ability to flexibly deploy the services anywhere on the ESB.

One other consideration is how the data is cached in the presentation tier. The Avitek demo relies on persisting a standard XML Schema to a relational database. However, in a diverse services environment with many varying units of information, it might be preferable to store and process XML of different formats without needing to define rigid relational structures. ESB providers may offer an embedded XML database, offering a "schema-less" approach to storage, retrieval, and query of XML documents, drastically reducing database administration time to accommodate changes in service data on the back end.

There are some alternative approaches that we should discuss here for comparison and contrast to the ESB. BEA WebLogic 8.1 offers several different approaches to provide this type of loosely coupled, reliable messaging between disparate domains.

Reliable Web Services
BEA WebLogic 8.1 provides a new feature called "Reliable SOAP Messaging." This feature allows asynchronous, reliable messaging between two different WebLogic servers. Although SOAP/Web services is a standards-based approach, WebLogic 8.1 currently implements reliability through proprietary SOAP headers and interaction protocol. It is assumed that the feature will some day be implemented using a standards-based approach such as "WS-Reliability." Even with a standard HTTP-based approach such as "WS-Reliability," certain use cases that require high throughput and low latency will be better served through a true "end-to-end" JMS solution.

To reliably connect two systems across disparate networks and geographies, some type of infrastructure must be colocated in each domain to provide the necessary "store and forward" functionality in the event of failures. ESB infrastructure is typically "lighter-weight," easily managed, and solely focused on integration services. Furthermore, deploying ESB infrastructure into a .NET environment, or even an alternative J2EE infrastructure, might be more palatable to the receiving organization. Planning for an ESB up front could certainly avoid problems down the road.

JMS Messaging Bridge
BEA WebLogic 8.1 offers a JMS messaging bridge that allows the ability to reliably forward messages between two different JMS implementations. While this certainly offers advantages over an HTTP/Web services approach, the infrastructure for the ESB provides the necessary forwarding, routing, and message optimization natively within the bus. The ESB also provides a cohesive management and security environment, simplifying deployment.

Federated Query
This "Federated Query" use case addresses the problem of needing to query multiple back-end systems from the presentation tier. Unlike the "Forward Service Cache" use case, the data in the back-end system can't reasonably be cached. There could be several reasons for this:
1.  The rate of data change in the back-end systems makes it unreasonable to cache the data: Querying the cached data could lead to data inconsistency and provide incorrect results.
2.  The volume of data is too great: It is not technically or economically viable to cache the data forward.

Another aspect of the federated service query pattern is that requests may take too long to complete (in some cases, days!). For example, a single system may involve some type of manual intervention (such as an approval) to complete the workflow. The ESB provides a great foundation for this pattern due to its inherent asynchronous nature.

The Federated Query pattern comes in at least two variants. The ones we discuss here vary based on the duration of the query.

For the two varieties of Federated Query patterns discussed in Table 1, the ESB exploits JMS's underlying "Publish-Subscribe" messaging paradigm to efficiently fan out requests to multiple back-end systems (in this case, subscribers). While these patterns illustrate a very simple approach to implement the functionality, the ESB provides the core facilities to implement a wide range of techniques. The ESB provides a rich set of communication models that can accommodate a wide variety of interactions between the portal and back-end systems with utmost efficiency.

To illustrate this point, let's consider a query to three back-end services. If each service took three seconds to process, invoking these services sequentially would take a minimum of nine seconds. The ESB allows the execution of the services to proceed in parallel, making the overall service execution time equal to the longest-running service (in this case, three seconds). While this may be implemented using a centralized, multi threaded technique, the ESB allows the concurrent processing to be distributed across the bus, eliminating the centralized bottleneck and providing greater scalability potential.

Federated Query: Real-Time Request
For this case, we will enhance Avitek to provide the ability for a physician to query multiple back-end systems to determine the list of patients who have received blood within a certain time frame. To implement this feature, we're going to take advantage of WebLogic Server 8.1's new "JMS Wrapper" support. This feature provides the ability to efficiently send or receive JMS messages directly from an EJB or a servlet. WebLogic Server 8.1 will efficiently manage a JMS connection pool to ensure messages are routed quickly between the portal application and the JMS Provider (or in our case, the ESB!). Here's how it works:

A stateless session bean contains a method that implements the widely accepted JMS "ReplyTo" pattern. When the client (servlet, JSP, or other) invokes the method on the stateless session bean, the method publishes the request to the ESB, which in turn fans out the request to services listening on the configured topic. Examples of such services are JMS clients, Web services, or even JCA Adapters interacting with applications.

The stateless session bean defines a method to allow the client to send an arbitrary string request. This could be formatted in XML.

public boolean sendRequest(String requestData, ArrayList a) {

Once the JMS objects have been established, the standard "JMSReplyTo" model is used to publish a request with the "return address". All responses will be returned to this instance of the stateless session bean (see Listing 1).

Finally, this example will wait for a specific number of responses from services on the ESB, or until a timeout occurs (see Listing 2).

Federated Query: Long Duration Request
For this case, we'll build on the previous example, but assume that responses from services on the bus will return in a much more unpredictable fashion. This pattern would allow the portal user to browse to other areas of the Web site, while responses asynchronously aggregate in the user's session. The user may even log out and log back in to check on the status of the request (see Figure 4).

For this case, a message-driven bean is used to asynchronously collect responses and persist them to a database. This is another case where a native XML database might come in handy. If systems respond with varying XML response information, it may be desirable to simply persist the entire XML response into the "schema-less" database.

One key characteristic of the ESB is that all services are tied together through a "loosely coupled" communications interface. One advantage relevant to this case is the ability for new systems to come online and be instantly included within the federated query. Since the underlying mechanism is "Publish-Subscribe," new services can simply subscribe to the relevant topics and receive query requests from the portal. An ESB permits dynamic discovery and intelligent, configuration-driven routing (content based, context based, etc.) at deployment time, allowing the portal to be shielded from service changes on the ESB.

Federated Query: Combination Real-Time and Long Duration Request In some cases, it may be desirable to gather results from various systems on the bus within a certain time frame (real-time request), but continue to collect the responses asynchronously after the initial time frame has expired (Long Duration Request). To accomplish this, we introduce the notion of a separate "Notification Topic" to allow the stateless session bean (SSB) to receive notifications when the MDB has successfully persisted a response to the cache. The SSB can use arbitrary business logic to determine when to stop waiting, allowing the portal application to read from the cache and present the results to the user (see Figure 5).

While BEA WebLogic Platform 8.1 is a robust platform capable of handling many application scenarios (including portals!), there are certain types of portal integration scenarios that require as the enterprise service bus. A fundamentally distributed network based purely on standards, the ESB will create highly agile, interoperable, and reliable service-oriented networks to link services together both within and beyond the enterprise. As Web service standards evolve to incorporate many of the semantics already available from JMS providers today, ESB providers will continue to implement standards and create interoperable networks that allow JMS apps to talk to Web services apps, and vice versa. In the meantime, an ESB will add significant value to portal and Web application developers attempting to solve complex integration scenarios involving heterogeneous systems, geographies, and organizations.

In our next article, we'll discuss how operational awareness, business activity monitoring, and integrated workflow can add additional value to these applications.

More Stories By Hub Vandervoort

Hub Vandervoort is vice president of Professional Services for Sonic Software. He has over twenty years experience as a consultant and senior technology executive in the networking, communications software, and Internet industries. Vandervoort previously co-founded three start-up ventures, including early message-oriented middleware (MOM) leader Horizon Strategies, Inc., which he merged with Momentum Software Corporation. He also co-founded, and served as board member of the Message-Oriented-Middleware Association (MOMA).

More Stories By Matt Rothera

Matt Rothera is a practice manager at Sonic Software (www.sonicsoftware.com), and works with customers to help plan, design, and deploy real-time, service-oriented architectures. With over 15 years of technical experience, Matt has worked with Fortune 100 customers to integrate their services with internal applications, business partners, and enterprise portals.

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