Patterns: Broker Interactions for Intra- and Inter-enterprise

Chapter 7. Technology options 135

model, for security, and for the coupling strength between requestor and

provider. The simplest effect is that parameters in Web services are

in-parameters and never in-out-parameters. To return a response value you have

to use the return value of the method.

The security impact results from the fact that in the case of CORBA or RMI the

client is remotely acting in the address space of the server application.

Reference errors can lead to server-side memory access exceptions or data

corruption, for example.

Furthermore, in the case of CORBA and RMI the structures of the stub objects

are identical to those on the server side. Changing the object structure on the

server side needs a refactoring of the clients. In the case of SOAP, no object

structures are exposed, except for methods which can have objects as

parameters and return values. Changing the object structure on the server side

need not lead to a refactoring of the client as a direct consequence.

7.4 J2EE Connector Architecture

The J2EE Connector Architecture is aimed at providing a standard way to access

enterprise applications from a J2EE-based Java application. It defines a set of

Java interfaces through which application developers can access heterogeneous

EIS systems, for example, legacy systems such as CICS, and Enterprise

Resource Planning (ERP) applications.

J2EE Connector Architecture 1.0 support is a requirement of the J2EE 1.3

specification. It provides access to a range of systems through a common client

interface API (CCI). Application programmers code to the single API rather than

having unique interfaces for each proprietary system. The link from the API to the

enterprise system is called a resource adapter and is provided by a third-party

vendor. This is somewhat analogous to the model for JDBC drivers. Resource

adapters are packaged as resource adapter archive (RAR) files.

IBM WebSphere Application Server V5.0 supports the J2EE Connector

Architecture 1.0, as required by the J2EE 1.3 specification. The administrative

console supports J2EE Connector resource adapter configuration. The

administrative console allows the association of connection factories for the

resource adapter that encapsulate the pooling attributes.

Component providers request a connection for an enterprise information system

(EIS) from the connection factory through the JNDI lookup mechanism. IBM

supplies resource adapters for enterprise systems such as CICS, HOD, IMS,

SAP, and Crossworlds as separate products.

136 Broker Interactions for Intra- and Inter-enterprise

IBM WebSphere Studio Application Developer V5.0 supports application

development using J2EE Connectors, and development of custom J2EE

Connectors.

7.4.1 CICS resource adapter

The CICS Transaction Gateway (CICS TG) V5 is a set of client and server

software components that allow a Java application to invoke services in a CICS

region.

The CICS TG offers three basic interfaces for Java clients:

򐂰 External Call Interface (ECI) for COMMAREA-based CICS applications

򐂰 External Presentation Interface (EPI) for 3270-based transactions

򐂰 External Security Interface (ESI) for password management to verify and

change user IDs and passwords

The CICS resource adapter is covered in detail in the following chapters.

7.4.2 IMS resource adapter

The IMS Connector for Java provides a way to create Java applications that can

access IMS transactions. The IMS Connector for Java uses IMS Connect to

access IMS. IMS Connect is a facility that runs on the host IMS machine and

supports TCP/IP and Local Option communication to IMS. A Java application or

servlet accesses IMS Open Transaction Manager Access (OTMA) through IMS

Connect. IMS Connect accepts messages from its TCP/IP clients and routes

them to IMS OTMA using the Cross-System Coupling Facility (XCF).

The runtime component of IMS Connector for Java is provided as a component

of IMS Connect, Version 1 Release 2 (Program Number 5655-E51). The J2EE

Connector implementation of this runtime component is also referred to as the

IBM WebSphere Adapter for IMS. It is packaged as a RAR file, imsico.rar, for

deployment into a WebSphere Application Server. The RAR file is installed to a

target directory from the IBM IMS Connect, Version 1 Release 2.

7.4.3 Advantages of J2EE Connectors

Some reasons to use J2EE Connectors are:

򐂰 The common client interface simplifies application integration with diverse

EISs. This common interface makes it easy to plug third-party or home-grown

resource adapters into your applications.