64 IBM Express Runtime V2.1
5.1 Exploring a wrapper
As used in Express Runtime V2.1, wrappers can be thought of as the “workflow” or
“controller” elements that are responsible for controlling the flow of execution for deploying a
component.
There are two types of wrappers:
򐂰 Application wrapper
򐂰 Solution wrapper
5.1.1 Application wrapper
In the context of Express Runtime V2.1, an application is best thought of as a component of
an overall solution. This can include a middleware component as well as an actual application
in the more generalized sense. For example, one component of a solution might be
WebSphere Application Server Express. Although this is a piece of middleware, it is still an
application in the terminology used by Express Runtime.
In order to integrate an application into a solution, a developer has to create a custom
wrapper for this application.
Each application wrapper contains of several XML files, user programs, and optionally other
artifacts, such as scripts, GIF files, and so on. These components are all contained within an
application project that you create using the Express Runtime Developer tool.
The XML files define the way the application is installed and configured on the target system.
One of these XML files called
application.axml. This is the most important file. It contains all
information about the user programs, application files, variables, and libraries.
User programs run during the application deployment to perform the installation, as well as
pre-installation or post-installation operations. User programs can be used to:
򐂰 Drive the installation of IBM middleware components as well as partners’ applications.
򐂰 Execute the DB2 scripts to create tables required for application and populate the table
with data.
򐂰 Configure middleware component, such as WebSphere Application Server Express, using
wsadmin scripts written in Jython or JACL.
User programs can use one of the several options, such as a return code, to indicate the
success or failure. A user program can be one of the following types:
򐂰
Java program.
򐂰
Custom program. It can be a custom script, executable or system command.
򐂰
InstallShield executable.
The typical choice for a user program type is a Java program.
After the application wrapper development completes, the application is packaged together
with the middleware components required to support the application. The component that
allows you to do this is called a
solution wrapper.
Important: Make sure you understand the term application as it applies to Express
Runtime V2.1. An
application is a building block of an Express Runtime solution. It can be
a J2EE application or a middleware component.

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