1. ZK, Spring & JPA On
Two PaaS Clouds
(Java MVVM Adventures Featuring
Heroku & Openshift)
Simon Massey

2. Overview
What is PaaS "Cloud" and why we should care?
Background to the ZkToDo2 sample app
Outline of the MVVM Pattern
Walk through of MVVM sample page (new ZK6
features!)
Quick pass of the Spring & JPA internals
The key ingredient: maven build profiles
Live push of source to two clouds! (Fingers
crossed!)

3. Clouds (In One Slide)
Clouds come "as a service" (aaS)
Software aaS
Infrastructure aaS
Platform aaS
SaaS is your data on the cloud with leased
software (they do everything)
IaaS is leased managed hardware (they can do
the network)
PaaS is leased application/database capacity
(they keep it running whilst you write the app)

4. The PaaS Proposition
Server virtualization is very mainstream. High
density host servers reduce overheads
Failover, off-site backup, standby servers, spare
parts, upgrades, network is divided by number
of virtual servers
Rent a "virtual private server" (VPS) and you
have to set it up and care for it yourself (logs
filling up your disks?)
How do you source 0.2 system adminstrators for
your app? And if they change jobs?
Outsource this to a PaaS provider!

5. The PaaS Proposition (2)
A big provider with a big server farm has
automated deployment "elastic platform"
Need more power? "Click here Sir to approve
the monthy credit card payments..."
Choice is a double edged sword; standardization
is the key to maintaining a large estate of
applications
Big cloud farms run thousands of servers and are
evolving best practice at a high rate
Running your own servers is very last century;
you can offload that work to the experts

6. Is Your PaaS RIA Friendly?
Not all PaaS clouds are AJAX friendly. Some
assume that you are hosting a blog (i.e.
stateless full page reload app)
Not all PaaS clouds provide a relational
database. ZK apps tend to be data orientated
desktop-like apps which need an RDBMS
J2EE is "complex" but PHP and Ruby are
"simple"(??). Java sat outside the party whilst
Ruby On Rails danced up a storm
… but now the big Rails clouds are doing Java
and are making it look very easy!

7. Interlude
Code https://github.com/simbo1905/ZkToDo2
Where is it running?
Redhat Openshift zktd2-zkdemo.rhcloud.com
Heruko glowing-light-1070.herokuapp.com
(note: apps may suspend when idle so may take
a long time to start on first hit)
What IDE, DB, etc?

8. The Code In Context
The "ZK ToDo 2" sample app has the same
screen implimented three times; using MVP,
MVC and ZK6 MVVM (aka MVB) patterns
Three ZK articles document the different patterns
in the code MVP (2007), MVC (2009), MVVM
(2011). MVVM article is out of date as sample
code now does ZK6 "ZK Bind" MVVM
Sample code has moved to the zktodo2 repo on
GitHub with an Apache2 license
The code now deploys to Heroku or Openshift
PaaS clouds!

9. About The Code
The "ZkToDo2" sample app (aka zktd2) is a
simple database CRUD app written with ZK,
Spring and JPA
Code uses a relational DB and has configurations
for HSQL, MySQL and PostreSQL databases
Spring instantiates the objects and wires them
together when the ZUL page "asks for" a
spring bean due to XML databindings
Leverages SpringMVC scopes and ZKSpring for
elegant care free coding

10. The MVVM Screen....

11. … is all databindings!
Your
ClickMe! 1 Java
2
ZK Web ZK
Desktop Bind
4 3
Saved! this.msg="Saved!"

12. Model-View-ViewModel
View == Web Desktop
Binder
<<reflection>>
Legend
ViewModel compiles to
command
DomainModel load

13. The ViewModel Class
[show code] org.zkforge.zktodo2.ZkToDoViewModel
Holds the List<Reminder> the user is working with
Holds the selectedItem Reminder the user is
currently editing
Uses the ReminderService which updates the
database
Has the add(), save(), delete() methods
Can be shared by different views
The view is active; "@bind" has AJAX updates write to
the selectedItem Reminder

14. Data Bindings
Page load calls getReminders on toDoViewModel
and renders each date in a list:
<window apply="org.zkoss.bind.BindComposer"
viewModel="@id('vm') @init(toDoViewModel2)">
<listbox model="@load(vm.reminders)"
selectedItem="@bind(vm.selectedReminder)">
<template name="model" var="reminder">
<listitem>
<listcell label="@load(reminder.date)"/>
</listitem></template</listbox></window>

15. Data Bindings 2
When the user selects a different reminder in the
list let the user edit it in the edit panel:
Date:<datebox
value="@bind(vm.selectedReminder.date)" />
The vm.selectedReminder is refered to in
multiple places. It is written to by the onSelect
Event of the Listbox:
<listbox model="@load(vm.reminders)"
selectedItem="@bind(vm.selectedReminder)">
ZKBind keeps track what it changes and reloads
UI with changed state

16. Command Bindings
New in ZK6!
<button label="Save" onClick="@command('save')"/>
There is zero code to read/write data between
screen and the JPA entites: binder is updating
them over AJAX
save() only calls save(selectedReminder) or
delete(selectedReminder)
The binder is a generic UI Controller
ZK Bind updates UI + Model + Entities
You just write very testable Java!

17. Less Boiler Plate Code
Java methods which change state have hints as
to what to reload into the screen:
@Command
@NotifyChange({"reminders","selectedReminder"})
public void delete() { .... }
Annotations on the Reminder entity setters and
on the ViewModel CRUD methods
Desktop "zul" is bound onto the ViewModel
Could make "admin screen" & "read-only
screen" for the same ViewModel (else "touch
screen" & "mouse screen")

18. Spring Bean XML Definitions...
ViewModel bean has "desktop" scope
<bean id="toDoViewModel2"
class="org.zkforge.zktodo2.ZkToDoViewModel"
p:reminderService-ref="reminderService" scope="desktop" />
So only one bean per web desktop (you may have many
desktops per http session)
... has singleton reminder service:
<bean id="reminderService"
class="org.zkforge.zktodo2.ReminderService"
p:basicDao-ref="basicDao" />
… has singleton basicDao:
<bean id="basicDao" class="org.zkforge.zktodo2.BasicDao"/
>

19. … Stable Since 2007
Same BasicDao for other patterns demo screens
These days you don't need the Spring XML.
Spring has alternative way to specificy how to
wire up the beans (with Java annotations)
CDI would not be hard at all (see zkcdi library)
Back-end code is "orthodox" allowing us to
focus on the code and what's new; ZK Patterns
… and deploying onto different Clouds!

20. ZK Cloud "Bake Off"
Two leading cloud providers chosen scientifically
and at random (google+beer)
Each backed by a major software company
(Salesforce vs Redhat)
Are they opensource like ZK, do they run it well,
and are they easy to use...?

21. What Do You Get?
Feature Heroku Openshift
Deploy from Yes. Git + Maven Yes. Git + Maven
source?[1]
Database? PostgreSQL MySQL
Container? Jetty7.4 JBossAS7.0
(embedded) (standalone)
Proprietary No problems for No problems for
Gotchas?[2] the sample app the sample app
[1] With Git you commit locally and "push" all the commits to one or
more repos. One remote repo is the cloud; it compiles+deploys
[2] ”Can I move my production app at any time to my own servers?”

22. The Maven Build Profiles
Develop and debug on the jetty-maven-plugin ”mvn
jetty:run” then deploy to JBoss, Weblogic,
Websphere or Tomcat when it is ready to user test
When in JUnit or debugging (jetty:run) Spring is
configured to setup the resources (datasource, jms)
To run in JBossAS7 Spring is configured to pull in the
platform resources (jndi-datasource, jndi-jms)
Maven build profiles swap the Spring configuration based on
a "-P" parameter using webapp "overlays"
Write once deploy to any cloud:
mvn -P "openshift" package
mvn -P "cloudX" package

23. Live Deploy Demo
This could be wishful thinking...!
[p.s. All went well, we committed a change to the
screen locally and with a single command
deployed to each of the two cloud services]

24. … And The Winner Is ...?
Both clouds are lightening fast for ZK AJAX!
Both have fully opensourced stacks!
Both are oh-so-easy-to-use

25. References
The code https://github.com/simbo1905/ZkToDo2
ZK6 MVVM introduction Hello ZK MVVM
MVC article Desktop MVC Patterns ZK, Spring & JPA
Original MVP article
SmallTalks 2008 Best MVC Patterns
Book on how to build a layered domain model with
Spring POJOs In Action
Martin Fowler GUI Patterns pages UI Architectures
Josh Smith's inspirational Microsoft .Net MVVM Article