Overview of J2EE Connector Architecture

The J2EE Connector Architecture provides a standardized way to connect an application component with Enterprise Information Systems (EISs). Examples of an EIS include a legacy-database system, an ERP system, or a transaction-processing system.

Note:
In the J2EE Connector Architecture specification 1.0., a connector is a client component that needs access to information in an EIS. This J2EE definition of connector differs from the WebSphere business integration system definition. In the WebSphere business integration system architecture, a connector is a WebSphere business integration system component that mediates between an EIS application and one or more collaborations within InterChange Server (ICS). For purposes of consistency with the J2EE Connector Architecture specification 1.0., this manual uses the J2EE definition of connector.

To provide standardized communication between the application component and the EIS, the J2EE Connector Architecture defines the following:

The following sections describe each of these standards in more detail.

Resource adapter

The resource adapter enables application components to communicate with an EIS. The application component sends requests for the EIS to the resource adapter. The resource adapter communicates directly with the EIS, returning any requested information to the application component. The application component and resource adapter communicate with each other through the Common Client Interface (CCI). CCI is a standard client API that the J2EE Connector Architecture specification 1.0. defines. Through CCI, an application component can request the following tasks from the resource adapter:

As both Figure 2 and Figure 3 show, the application component and the resource adapter use CCI calls to communicate.

The resource adapter communicates directly with the EIS through the EIS-specific API. It implements the CCI interfaces through calls to this EIS-specific API. By isolating the EIS-specific API calls to the resource adapter, application components do not need to know this API. Instead, the application component uses the high-level CCI calls to request EIS services through the resource adapter.

Environments for calling a resource adapter

Table 1 shows the two environments that the J2EE Connector Architecture specification 1.0. defines, in which an application component can access an EIS through a resource adapter.

Table 1. Environments for using a resource adapter to access an EIS

J2EE connector adapter environment Application component Description
Managed environment A server-side application component Contacts an application server, which communicates with the EIS through the resource adapter
Non-managed environment A client application Contacts the resource adapter directly to communicate with the EIS

The following sections describe each of these environments in more detail.

Managed environment

In a managed environment, an application server provides basic services to J2EE application components that need to access Enterprise Information Systems (EISs). The application component is a server-side module that the application server manages. Examples of managed application components include an Enterprise JavaBean (EJB), a Java Server Page (JSP), or a servlet.

To communicate with an EIS, the client application notifies the appropriate application component in the application server that it needs information. The application server and the application component work together with the resource adapter to establish and manage this connection. The application server is responsible for requesting a connection to the EIS. If a connection is not available, the application server requests one from the resource adapter associated with the EIS. The application component receives a handle for this connection.

The application server can provide interactions with many EISs because the J2EE Connector Architecture specification 1.0. defines system-level contracts, which define the interaction between the application server and the resource adapter. These system-level contracts define the following interactions:

The benefit of accessing an EIS through an application server is that the application component is relieved of the need to know the details of connection management, security management, and transaction management. The application server performs these tasks and enforces them through system contracts, to which both the application server and each resource adapter must adhere.

Figure 2 shows the managed environment of the J2EE Connector Architecture, which uses an application server to manage communication between application components and resource adapters.

Figure 2. Managed environment: Accessing an EIS through an application server

The figure is a schematic of the managed environment of the J2EE Connector Architecture, which uses an application server to manage communication between application components and resource adapters. The center of the image is a large shaded rectangle denoted "Application Server". Within this box are several sub-nodes. There are three nodes across the top labelled: "Connection manager", "Security manager" and "Transaction manager" each of these is connected via a slanted line to a box labelled "Resource adapter". The connections between the managers and the "Resource adapter" are denoted "System-level contracts". Also in the "Application server" area is a node labelled "Server-side application component" which is connected to the "Resource adapter" with a horizontal line. which is denoted "CCI". The "Application Server" area of the image is flanked on the left by a node labelled "Client component" which has a connection drawn to the "Server-side application component" and on the right by a node called "EIS" which is shown with a connection to the "Resource adapter".

In Figure 2, notice that the system-level contracts define the interactions between the resource adapter and the application server while the CCI defines the interaction between the resource adapter and the application component.

Non-managed environment

In a non-managed environment, the application component is the client application, which communicates directly with the resource adapter to access Enterprise Information Systems (EISs). Examples of non-managed application components include Java applications and applets. Figure 3 shows the non-managed environment of the J2EE Connector Architecture, in which the client application uses CCI calls to communicate with the resource adapter.

Figure 3. Non-managed environment: accessing an EIS directly

The figure shows how an EIS can be accessed directly in a non-managed environment. The image comprises three rectangles arranged horizontally with connecting horizontal lines between successive boxes. From the left the boxes are labelled: "Client application", "Resource adapter" and "EIS". There is a heading above the "Client application": "Application component". The connection between the "Client application" and the "Resource adapter" is labelled "CCI".

When executing in the non-managed environment, the client application must provide the connection management, security management, and transaction management.

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