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[wtp-dev] Re: Server API change proposal
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I personally think publishing at the app level is a more natural/
logical approach and the need of a second delegate class should be
only temporary until other server adapters can conform to this
proposal. I also have some concerns on how the delta is managed and
flushed, but need some time to gather my thoughts so that can be
discussed later.
- sachin
On Mar 20, 2006, at 7:01 PM, Thomas Yip wrote:
Introduction
This proposal briefs the limitation we see with current server
publish API, and it suggests a solution. We had a short discussion
during a conference call on Mar 13th, 2006. (mainly around the
ServerBehaviourDelegate). The problem is also related to https://
bugs.eclipse.org/bugs/show_bug.cgi?id=123676
Current API
We learned the original design was driven by a need of a very
simply publish mechanism.
an adopter should able to implement a simply delegate and do the
publish work.
publish tasks was intent to be simple task.
most methods can be overridden.
BEA use-cases
We found the current API is not ideal for BEA needs.
We delay much of publish process until user do an explicit publish
action (menu item publish, or Run on Server).
We generates *.java file based on annotation of Java file in
publish time. We trigger project rebuild during process.
We insert information into application descriptors (web.xml,
application.xml) based on files on the project.
Generated artifacts can cause changes to the EAR or other modules
in the same application.
Publish application by application.
Publish failure should be isolated between modules.
For us, the publish process is better described as a 3 steps
process: Assembly (artifact generation), Packaging (we package
virtually), and Distribution (calls JSR-88 to distribute the
application to the server).
Limitation
The current SPI was driven by the need of simple publishing. The
publish process iterates module by a flattend module list (not
application by application.)
Because that most methods can be overridden, we can achieve our
goal reasonably well. However, it incurs maintenance risk, because
are not really implementing the delegate’s SPI. For example,
if a fix or an enhancement is made to PublishOperation, our server
adapter lag behind, and enhancement will not be supported.
We short circuit a few methods, such as publishModules() (which is
a violate the interface). If any of the methods is called by new
code that we haven’t overridden, it causes unexpected behaviour.
Because of the different design goal, we don’t implement the full
spec of ServerBehaviourDelegate. While such changes might not be
likely, an adopter should not be required to implement their
delegate in a way to violate the SPI contract.
SolutionRequired changes
We can eliminate the problem by the following changes:
Introduce another delegate. Let’s call it
BaseServerBehaviourDelegate for now. The current
ServerBehaviourDelegate should make extended of
BaseServerBehaviourDelegate. Most generic methods can be push up.
(such as state settings, module controls, resource delta
maintaince. But, it leaves out
code related to published module list, and the kind.
PublishOperation, and
all the publish methods. Introduce an adapter interface to indicate
PublishOperation is supported.
The changes will maintain compatibility for all current adopter,
and the original design goal. It enables adopter with different
needs to have full control of the publish process.
Either, makes publish operation optional. Push down
PublsihOperation related code to the original ServerBehaviour
Delegate.
Or, factors out PublishOperation into utility class or method.
Or, made PublishOperation not depends on the flatten module path
(IModule[] representing the sub module and its parents).
Introducing another extension point for UI to replace the hard-
coded publishTask page fragment. Move UI for publishOperation as an
extension.
A brief study of the code indicated that we should able to
implement it in a way that it doesn’t affect existing adopter.
Optional changes
A few optional changes can be introduced to ease the work of an
adopter.
Publishing application-by-application is common to many servers. We
might want to introduce another BehaviourDelegate.
Generic server is already use application-by-application approach.
We should look into merging the requirements.
Going further, we can also introduce the 3 steps publish process
for adopter with complicated publish use-case.
--------------------
Thomas Yip
Senior Software Engineer
BEA Systems
Email: tyip@xxxxxxx YIM: thomasleaf Phone: (206) 926-2906
Blog: http://theBigGrid.com/
"The complexity you remove can never fail." Burt Rutan.
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