= Application Composer History
:jbake-type: page
:jbake-status: published
:index-group: Testing

ApplicationComposer can look like a long story but following it you'll
realize it is finally quite natural.

== Internal tool

TomEE (former OpenEJB) is an Application Server. One of the most
important task writing an Application Server is to ensure the
implemented features do what is expected. However it is hard to write N
test applications, in N modules to ensure it works smoothly. In
particular when you want to test a small part of the whole server.

So you immediately think to mocking what is not needed. It works but has
a big pitfall: test is often a noop or hide a lot of issues.

So the idea came to be able to shortcut the part we don't care much
about runtime: the application packaging.

Here what is the ApplicationComposer: an (originally test) API to create
a EE application programmatically.

== Designs

ApplicationComposer design was aligned on this simple need. An
ApplicationComposer "test" (browsing other pages you'll see it is much
more than test today) is composed of mainly 2 parts:

* modules: methods describing a module of an application. It can be a
persistence.xml, an ejb-jar.xml, a web.xml...but all programmatically.
* configuration: container configuration allowing to interact with
container (creating resources for instance)

== Test but not only

ApplicationComposer was originally a JUnit only runner but was pretty
quickly extended to TestNG too and today you can even use it to write
`main(String[])` - even in a shade!

API was greatly simplified and it allows you pretty easily to deploy
with a simple shade a JAXRS/JAXWS/JMS service!

== Going further

If you want to go further you can browse:

* link:getting-started.html[Getting Started]
* link:advanced.html[Advanced]