ZK, Spring & JPA On Two PaaS Clouds

(Java MVVM Adventures Featuring Heroku & Openshift)

Simon Massey

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!)

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)

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!

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

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!

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?

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!

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

The MVVM Screen....

… is all databindings!

ZKBind

ZK WebDesktop

ClickMe!

this.msg="Saved!"

12

4

YourJava

3Saved!

Model-View-ViewModel

Legendcompiles to

command

load

View == Web Desktop

Binder

ViewModel

DomainModel

<<reflection>>

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

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>

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

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!

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")

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"/>

… 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!

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...?

What Do You Get?

Feature Heroku Openshift

Deploy from source?[1]

Yes. Git + Maven Yes. Git + Maven

Database? PostgreSQL MySQL

Container? Jetty7.4 (embedded)

JBossAS7.0 (standalone)

Proprietary Gotchas?[2]

No problems for the sample app

No problems for 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?”

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

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]

… And The Winner Is ...?

Both clouds are lightening fast for ZK AJAX!

Both have fully opensourced stacks!

Both are oh-so-easy-to-use

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