Programming WebLogic Server J2EE Connectors
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Overview of WebLogic J2EE Connectors
The following sections provide an overview of WebLogic J2EE connectors (also referred to as resource adapters):
- WebLogic J2EE Connector Terminology
- Overview of the BEA WebLogic J2EE Connector Implementation
- J2EE Connector Architecture Components
WebLogic J2EE Connector Terminology
Key terms and concepts that you will encounter throughout this documentation include the following:
- Application Component—can be a server-side component, such as an EJB, JSP, or servlet, that is deployed, managed, and executed on an application server. It can also be a component executed on the Web-client tier but made available to the Web-client by an application server. Examples of the latter type of application component include a Java applet and a DHTML page.
- Caller Principal—a principal that is associated with an application component instance during a method invocation. For example, an EJB instance can call the getCallerPrincipal method to get the principal associated with the current security context.
- Common Client Interface (CCI)—defines a standard client API for application components and enables application components and Enterprise Application Integration (EAI) frameworks to drive interactions across heterogeneous EISes using a common client API. BEA defines a CCI for EIS access.
- Connection—provides connectivity to a resource manager and enables an application client to connect to a resource manager, perform transactions, and access services provided by that resource manager. A connection can be either transactional or non-transactional. Examples include a database connection and an SAP R/3 connection.
- Container—part of an application server—such as WebLogic Server—that provides deployment and run-time support for application components. A container allows you to monitor and manage supported components as well as the service(s) that monitor and manage the components. Containers can be one of the following:
- Connector containers that host resource adapters
- Web containers that host JSP, servlets, and static HTML pages
- EJB containers that host EJB components
- Application client containers that host standalone application clients
- Credential—contains or references security information that can authenticate a principal to additional services. A principal acquires a credential upon authentication or from another principal that allows its credential to be used: the latter is termed principal delegation.
- Enterprise Information System (EIS)—provides the information infrastructure for an enterprise. An EIS offers a set of services to its clients. These services are exposed to clients as local and/or remote interfaces. Examples of an EIS include:
- Enterprise Information System (EIS) resource—provides EIS-specific functionality to its clients. Examples of an EIS resource include:
- Record or set of records in a database system
- Business object in an Enterprise Resource Planning (ERP) system
- Transaction program in a transaction processing system
- Initiating Principal—the security principal representing the end-user that interacts directly with the application. An end-user can authenticate using either a Web client or an application client.
- J2EE Connector—a system-level software driver used by an application server such as WebLogic Server to connect to an EIS. BEA supports connectors developed by Enterprise Information Systems (EISes) vendors and third-party application developers that can be deployed in any application server supporting the Sun Microsystems J2EE Platform Specification, Version 1.3. Resource adapters contain the Java, and if necessary, the native components required to interact with the EIS.
- J2EE Connector Architecture—an architecture for integration of J2EE-compliant application servers with enterprise information systems (EISes). There are two parts to this architecture: an EIS vendor-provided resource adapter and an application server—such as WebLogic Server— to which the resource adapter plugs in. This architecture defines a set of contracts—such as transactions, security, and connection management—that a resource adapter has to support to plug in to an application server. BEA also defines a Common Client Interface (CCI) for EIS access. The CCI defines a client API for interacting with heterogeneous EISes.
- Managed Environment—defines an operational environment for a J2EE-based, multi-tier, Web-enabled application that accesses EISes. The application consists of one or more application components—EJBs, JSPs, servlets—which are deployed on containers. These containers can be one of the following:
- Web containers that host JSP, servlets, and static HTML pages
- EJB containers that host EJB components
- Application client containers that host standalone application clients
- Non-managed Environment—defines an operational environment for a two-tier application. An application client directly uses a resource adapter to access the EIS; the EIS defines the second tier for a two-tier application.
- Principal—an entity that can be authenticated by an authentication mechanism deployed in an enterprise. A principal is identified using a principal name and authenticated using authentication data. The content and format of the principal name and the authentication data depend upon the authentication mechanism.
- RAR—resource adapter archive. A compressed (.zip) file used to load classes and other files required to run a resource adapter.
- ra.xml—describes the resource adapter-related attributes type and its deployment properties using a standard DTD from Sun Microsystems.
- Resource Adapter—see J2EE Connector.
- Resource Manager—part of an EIS that manages a set of shared EIS resources. Examples of resource managers are a database system, a mainframe TP system, and an ERP system. A client requests access to a resource manager to use its managed resources. A transactional resource manager can participate in transactions that are externally controlled and coordinated by a transaction manager. In the context of the WebLogic J2EE connectors, clients of a resource manager can include middle-tier application servers and client-tier applications. A resource manager is typically a different address space or on a different machine from the client that accesses it.
- Resource Principal—a security principal under whose security context a connection to an EIS instance is established.
- Security Attributes—a principal has a set of security attributes associated with it. These are related to the authentication and authorization mechanisms. Examples are security permissions and credentials for a principal.
- Service Provider Interface (SPI)—contains the objects that provide and manage connectivity to the EIS, establish transaction demarcation, and provide a framework for event listening and request transmission. All J2EE Connector Architecture-compliant resource adapters must provide an implementation for these interfaces in the javax.resource.spi package.
- System Contract—a mechanism by which connection requests are passed between entities. To achieve a standard system-level pluggability between application servers such as WebLogic Server and EISes, the J2EE Connector architecture defines a standard set of system-level contracts between an Application server and an EIS. The EIS side of these system-level contracts is implemented in a resource adapter.
- weblogic-ra.xml—adds additional WebLogic Server-specific deployment information to the ra.xml file.
Overview of the BEA WebLogic J2EE Connector Implementation
BEA WebLogic Server continues to build upon the implementation of the Sun Microsystems J2EE Platform Specification, Version 1.3. The J2EE Connector Architecture adds simplified Enterprise Information System (EIS) integration to the J2EE platform. The goal is to leverage the strengths of the J2EE platform—including component models, transaction and security infrastructures—to address the challenges of EIS integration.
The J2EE Connector Architecture provides a Java solution to the problem of connectivity between the multitude of application servers and EISes. By using the Connector Architecture, it is no longer necessary for EIS vendors to customize their product for each application server. By conforming to the J2EE Connector Architecture, BEA WebLogic Server does not require added custom code in order to extend its support connectivity to a new EIS.
The J2EE Connector Architecture enables an EIS vendor to provide a standard resource adapter for its EIS. This resource adapter plugs into WebLogic Server and provides the underlying infrastructure for the integration between an EIS and WebLogic Server.
By supporting the J2EE Connector Architecture, BEA WebLogic Server is assured of connectivity to multiple EISes. In turn, EIS vendors must provide only one standard Connector Architecture-compliant resource adapter that has the capability to plug into BEA WebLogic Server.
Note: This version of BEA WebLogic Server is completely compliant with J2EE 1.3.
J2EE Connector Architecture Components
The J2EE Connector Architecture is implemented in an application server such as WebLogic Server and an EIS-specific resource adapter. A resource adapter is a system library specific to an EIS and provides connectivity to the EIS. A resource adapter is analogous to a JDBC driver. The interface between a resource adapter and the EIS is specific to the underlying EIS; it can be a native interface.
The J2EE Connector Architecture has three main components:
- System-level Contracts—between the resource adapter and the application server (WebLogic Server)
- Common Client Interface (CCI)—provides a client API for Java applications and development tools to access the resource adapter
- Packaging and Deployment Interfaces—provides ability for various resource adapters to plug into J2EE applications in a modular manner
The following diagram illustrates the J2EE Connector Architecture:
Figure 1-1 J2EE Connector Architecture
A resource adapter serves as the "J2EE connector." WebLogic Server supports resource adapters developed by Enterprise Information Systems (EISes) vendors and third-party application developers that can be deployed in any application server supporting the Sun Microsystems J2EE Platform Specification, Version 1.3. Resource adapters contain the Java, and if necessary, the native components required to interact with the EIS.
System-level Contracts
The J2EE Connector Architecture specification defines a set of system-level contracts between the J2EE-compliant application server (WebLogic Server) and an EIS-specific resource adapter. WebLogic Server, in compliance with this specification, has implemented a set of defined standard contracts for:
- Connection management—a contract that gives an application server pool connections to underlying EISes. It also allows application components to connect to an EIS. This results in a scalable application environment that supports a large number of clients requiring access to EISes.
Note: For more information on connection management, refer to Connection Management.
- Transaction management—a contract between the transaction manager and an EIS supporting transaction access to EIS resource managers. This contract allows an application server to use a transaction manager to manage transactions across multiple resource managers.
Note: For more information on transaction management, refer to Transaction Management.
- Security management—a contract that provides secure access to an EIS and provides support for a secure application environment. This reduces threats to the EIS and protects information resources that the EIS manages.
Note: For more information on security management, refer to Security.
Common Client Interface (CCI)
The Common Client Interface (CCI) defines a standard client API for application components. The CCI enables application components and Enterprise Application Integration (EAI) frameworks to drive interactions across heterogeneous EISes using a common client API.
The target users of the CCI are enterprise tool vendors and EAI vendors. Application components themselves may also write to the API, but the CCI is a low-level API. The specification recommends that the CCI be the basis for richer functionality provided by the tool vendors, rather than being an application-level programming interface used by most application developers.
Further, the CCI defines a remote function-call interface that focuses on executing functions on an EIS and retrieving the results. The CCI is independent of a specific EIS; for example: data types specific to an EIS. However, the CCI is capable of being driven by EIS-specific metadata from a repository.
The CCI enables WebLogic Server applications to create and manage connections to an EIS, execute an interaction, and manage data records as input, output or return values. The CCI is designed to leverage the JavaBeans architecture and Java Collection framework.
The J2EE Connector Architecture recommends that a resource adapter support CCI as its client API, while it requires that the resource adapter implement the system contracts. A resource adapter may choose to have a client API different from CCI, such as the client API based on the Java Database Connectivity (JDBC) API.
Note: For more information relating to the Common Client Interface, refer to Client Considerations.
Packaging and Deployment
The J2EE Connector Architecture provides packaging and deployment interfaces, so that various resources adapters can easily plug into compliant J2EE application servers such as WebLogic Server in a modular manner.
Figure 1-2 Packaging and Deployment
A resource adapter provider develops a set of Java interfaces and classes as part of its implementation of a resource adapter. These Java classes implement J2EE Connector Architecture-specified contracts and EIS-specific functionality provided by the resource adapter. The development of a resource adapter can also require use of native libraries specific to the underlying EIS.
The Java interfaces and classes are packaged together (with required native libraries, help files, documentation, and other resources) with a deployment descriptor to create a Resource Adapter Module. A deployment descriptor defines the contract between a resource adapter provider and a deployer for the deployment of a resource adapter.
You can deploy resource adapter module as a shared, stand-alone module or packaged as part of an application. During deployment, you install a resource adapter module on an application server such as WebLogic Server and then configure it into the target operational environment. The configuration of a resource adapter is based on the properties defined in the deployment descriptor as part of the resource adapter module.
Note: For more information on packaging and deployment, refer to Packaging and Deploying Connectors.
