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Dynamic and rich web
application using the
good ol' JVM
Daniel López Janáriz
Web developer
Universitat de les Illes Balears (UIB)
December 9th 2010 JavaTools Community @ java.net
JavaOne 2010 JavaOneSM Brazil 2010 | Dec. 9th | Sala 3 | 2:00 PM | http://www.oracle.com/br/javaonedevelop/en/

Introduction

Web applications turned the development world upside
down.
Ever changing requirements
Heterogeneous equipment (client OS, browsers,
application servers, server OS)
Heterogeneous teams (programming, designing,
SEO, accesibility, usability...)
Development in “web time”
“Peter Pan” technology
And then we have to choose...

JavaOneSM Brazil 2010 | Dec. 9th | Sala 3 | 2:00 PM | http://www.oracle.com/br/javaonedevelop/en/

Dynamic and rich web application using the good ol\' JVM - Java One Brazil

Introduction II

What technology?
How to choose?
Which ones to try?
What is important?
Adoption?
Compatibility?
Background?
Is there any “magic bullet”?
That makes our team look like this...


Introduction III

How can we improve the situation:
Learn the various choices you can make so you can
decide between them
Adapt your architecture to the web development
world.
So, we are here to:
Showcase some technologies that can be used in
the Java plattform.
Demonstrate that an architecture can be adaptable.
The end goal is that the choice looks like...


Learning: why the JVM?

Java is/was popular for a reason. Among other things
Very good virtual machine
Tons of libraries, utilities, frameworks, API...
So, should we start from scratch?
Sometimes not possible (100% one-step migration)
Small steps help you move from a safe location to a
closer safe location.


Learning: how?

The JVM is a bytecode interpreter/dynamic compiler
so...
Generate compatible bytecode from the new
language. (ex. Scala)
Implement in bytecode an interpreter for the new
language. (ex. BeanShell)
Combine both solutions. (ex. Groovy)
The “interpreted” languages can be accessed
Through a custom API
Through the Java Scripting API (JSR-232, Java >=6)


Learning: Java Scripting API

ScriptEngineManager theScriptEngineManager = new ScriptEngineManager();
ScriptEngine theSE = theScriptEngineManager.getEngineByExtension(extension);
Reader reader = ...;
...
// To interpret the script directly
theAnswer = theSE.eval(reader);

// If you call a function inside the script
theSE.eval(reader);
Invocable inv = (Invocable) theSE;
theAnswer = inv.invokeFunction(functionName);


Architecture: How to be prepared?

In order to be able to adapt to different requierements,
we will use an architecture built around the Separation
of Concerns (SoC) pattern.
The overall goal is to have an architecture where the
different parts communicate through clearly defined
interfaces, so the don't step into each other toes.
Using an “opinionated” artechitecture with tight
integration brings other advantages and drawbacks.


But don't go overboard with it or...

Architecture: Tiers

This is the web development SoC
architecture we have used
Where we have separated these main
Concerns:
User interface
Presentation logic
Controller
Application/business logic
Persistence


Architecture: Showcase application

A simple CRUD application on one table(Items).
Every “concern” is implemented with different technologies:
To test if they really can be used independently.
To find out some of the benefits and drawbacks of each
alternative.
To do some mythbusting!


Showcase: Implementations

Persistence
Oracle, HSQLDB
Business logic
JDBC, Hibernate, JPA, Ibatis, Groovy(x2), JRuby, JavaScript(x2),
Jython, Scala, Pnuts, PHP, PL/SQL
Controller
WebLEAF
Presentation logic
JSP, FreeMarker, XSLT, Groovlets
User interface
HTML, RIA: JavaScript (ExtJS, GWT), Flex, Java (Applet, JWS)
Comunications
JSON, XML/HTTP, Web Services


951
Possibilities!!
( 495 if we exclude the DB)

App. Logic: Java/JDBC


App. Logic: Groovy


App. Logic: Jython


App. Logic: Scala


UI: HTML


UI: JavaScript RIA


UI: Flex RIA


UI: Java Applet RIA


UI: PDF


Etc... (demo)

http://localhost:8080/

http://www.greeneyed.org/test/


Conclusions

The JVM is not only Java and you don't have to abandon completely the Java
platform.
There are many different languages with different styles that are more or less
useful depending on your needs.
Learning different approaches to face all the different challenges is the way
to be prepared.
SoC architectures are an option to facilitate having different approaches at
hand, even though it's not the only one and it is not necessarily the best.
Implementing such an experiment is quite an experience and acts as a
vaccine against language bigotry.
Next question is... is any of this really useful in real life?
We have alredy used it to migrate the business logic from one
option to another and reduce memory consumption and CPU load
on the DB to move it to the application server so clustering of
those elements is more effective.
We have also used it to modify and “spice up” some UIs with some
AJAX/JavaScript widgets.


Thank you for your attention

Questions?


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Dynamic and rich web application using the good ol\' JVM - Java One Brazil

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Dynamic and rich web application using the good ol\' JVM - Java One Brazil