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Application Integration
Historically, enterprise information systems (EIS), such as legacy mainframe systems, and, more recently, commercial applications, such as ERP and CRM, have been at the center of the modern IT environment, driving enterprise-wide business functions, and providing critical data for enterprise operations. Today these systems are still vital to many businesses, but they are not the only systems on which businesses rely. In e-business environments, these systems must be linked not only with one another, but also with Web and wireless applications that enable the real-time exchange of information and services by customers, suppliers, and trading partners around the world.
To meet this demand, WebLogic Integration provides an application integration framework that enables intra-enterprise integration through the use of adapters. WebLogic Integration also provides an Adapter Developer Kit (ADK) that businesses can use to develop custom adapters. Using adapters, businesses can share data and business processes between connected applications without having to change their original applications or data structures.
The following sections describe the application integration functionality provided by WebLogic Integration:
Application Integration Framework
The applicaton integration framework provides the following key features to enable the integration of diverse enterprise systems:
The following sections provide details about each of these features.
Hosting J2EE CA-Based Adapters
The traditional approach to enterprise application integration is to connect individual systems with each other; in effect, to hardwire the systems together. This approach is fraught with complexity because connecting different systems requires an intimate, low-level knowledge of each proprietary technology. To remove this complexity, businesses use adapters.
Figure 3-1 EIS Adapters
Adapters are software components that applications can use to access enterprise data programmatically. For example, an adapter can use a Java class to represent enterprise data, and it can provide methods that applications can invoke to access the data. When an application invokes an access method, the adapter executes the method to retrieve the enterprise data. The widespread adoption of standards, such as J2EE and XML, has laid the groundwork for a standardized approach to the development of adapters. Perhaps the most significant of these standards for application integration is the J2EE Connector Architecture (CA). J2EE CA provides a standardized approach for the development of adapters for all types of applications—from legacy mainframe applications, such as CICS, to packaged applications, such as PeopleSoft, Siebel, and SAP. The adoption of standards such as J2EE CA enables businesses to develop adapters that work on any J2EE-compliant application server, such as WebLogic Server. WebLogic Integration builds on this standardized approach in its application integration framework by providing a standards-based architecture for hosting J2EE CA-based adapters. Using the ADK, developers can build J2EE CA-compliant adapters, and then deploy them in the integration framework to connect enterprise applications to WebLogic Server. Application Views The integration framework goes one step beyond the programmatic access adapters provide to enterprise systems with an innovation that makes it possible to expose existing information systems as business services. This innovation is called the application view of the adapter. The application view provides a business-oriented way for integration specialists to access enterprise data without worrying about the programmatic details defined in an adapter. Figure 3-2 Adapters and Application Views
The idea behind application views is quite simple. First, a developer codes an adapter that connects the enterprise system to WebLogic Server. The adapter exposes the functionality in an application that accesses enterprise data. The functionality the adapter exposes might, for example, update records in a database using SQL statements, or it might request information from an SAP system using its BAPI or IDOC interfaces. Then, a business analyst, working with the developer, defines an application view of the adapter using the Applicaton View Console provided by WebLogic Integration. Figure 3-3 WebLogic Integration Application View Console
The application view abstracts the technical details in the adapter so that a business analyst can invoke the functionality in the enterprise application exposed by the adapter without worrying about the technical implementation. For example, to update records in a database using SQL statements, a business analyst can define an application view called UpdateRecords. An EIS specialist supplies the SQL statements that update the database records, and includes them in the application view definition. At run time, the application view called UpdateRecords is invoked by an XML message from a business process. The application view, in turn, calls the adapter, passing the SQL statements to it. The adapter accesses the enterprise data and returns the result to the UpdateRecords application view, which returns the result in another XML message to the business process. Application View Benefits Using application views makes it possible to expose existing enterprise applications as business services that accept XML data as input and return XML data as output. Using XML as the common format to represent enterprise data makes it possible to treat different systems in similar ways. The basic difference between integrating with a SAP system and a Siebel system, from the perspective of the business analyst, is the content of the XML messages. The technical details of the system being integrated are made transparent, enabling the business analyst to focus on the business service being called to solve a business problem. Application View Services and Events Adapters can be developed as service or event adapters. A service adapter invokes a specific function in the enterprise system to which it is connected. An event adapter propagates information from the enterprise system to the integration environment. Businesses can add any number of services and events to each application view definition to support specific types of transactions between WebLogic Server and the target enterprise system. Figure 3-4 Application View Services and Events 
When added to an application view, each event responds to a particular enterprise application state. When a particular event is triggered, the event adapter extracts data about the event from the enterprise system, and propagates the data in an XML document to the WebLogic Integration environment using an application view. Similarly, when added to an application view, each service represents a particular function in the enterprise system. When the application view receives an XML document that maps to a particular service, it invokes the corresponding function in the enterprise system using the service adapter. The enterprise system may or may not send a response to the service, depending on how it is designed.
Integration with Business Processes
WebLogic Integration provides a plug-in framework that enables the integration of application views with business processes. To integrate application views with business processes, integration specialists do the following:
Using this scheme, application views can be updated without disturbing the business processes that use them, even if the implementation details of the application views change.
Adapter Development Kit
WebLogic Integration provides an Adapter Development Kit (ADK) that businesses can use to develop service and event adapters that run in any J2EE-compliant environment, such as WebLogic Server. The ADK provides the following collection of frameworks for the development, testing, packaging, and distribution of adapters:
Sample DBMS Adapter
WebLogic Integration includes a sample DBMS adapter. The sample is a J2EE CA-compliant adapter built using the ADK that provides a way for an application to access a relational database. Developers can use the sample adapter to learn how to develop adapters using the ADK.
The sample adapter includes the following features:
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