JAVA EE 6 Best Practices for Migrating Spring to WTF ?!?

JAVA EE 6

Best Practices for Migrating

Spring to

WTF ?WTF ?!?!?

Bert Ertman

Fellow at Luminis in the Netherlands

JUG Leader for NLJUG and a Java Champion

Who is this talk for?

You are using old school Spring and wonder how to move forward

Java EE seems to be hot again, should you jump on this train?

You love the J2EE Design and Development book; but is it still actual?

Why listen to us?We’re not working for an application server vendor

We’re no Rod Johnson groupies either

We’ve worked extensively with J2EE, Spring and modern Java EE

Had endless Java EE vs. Spring discussions...

Why migrate?

Spring is proprietary technology

Upgrading from old school Spring requires a lot of work anyway

Why not take it to the standard?

Scenario A

But now we want this

Let’s get a couple of

misunderstanding out of the way

first...

Isn’t Java EE too fat?

Startup times with application deployed

JBoss AS 7 ~2 seconds

Glassfish V3 ~4 seconds

Tomcat 6 + Spring ~4 seconds

Java EE 6 WAR file < 100kb

But I need Dependency

Injection• Java EE 6 introduced

CDI

•More powerful, contextual DI model

•Makes the platform extensible in a standard way

But I need AOP!Really?

You love getting your code all asymmetric and unreadable?

Or are you just using AOP light a.k.a. Spring AOP a.k.a. (Java EE) Interceptors?

Do I need heavy tooling?

Capabilities comparison

Capability Spring JavaEEDependency

InjectionSpring Container CDI

Transactions AOP / annotations EJB

Web framework Spring Web MVC JSF

AOP AspectJ (limited to Spring beans) Interceptors

Messaging JMS JMS / CDI

Data Access JPA / JDBC templates / other ORM JPA

RESTful Web Services

Spring Web MVC (3.0) JAX-RS

Integration testing Spring Test framework Arquillian *

* Not part of the Java EE specification

It can all be done using plain vanilla light weight Java

EE

rm -Rf spring*

?

Sure it would be fun!

realistic?

Typical old school Spring app

lots of complex XML, no annotations

old / outdated ORM solution

(JDBC Templates, Kodo, Toplink etc.)

deprecated extension based Web MVC (SimpleFormController etc.)

Migration Path

1.Upgrade Spring version

2.Replace old frameworks (ORM, web framework) within Spring

3.Run Spring and Java EE container side by side

4.Replace Spring entirely

5.Remove Spring container

Migration Path



3.Run Spring and Java EE container side by side



Upgrade Spring version

Upgrade Spring runtime (replace JAR files)

No code / configuration changes

Migration Path



3.Add Java EE code, keep old Spring code



Replace old frameworks within Spring

presentaton

layer

Data / Integratio

nlayer

Web MVC

Tasks

Spring JDBC Templates

Kodo

@AutoWired

businesslayer

JMS beans

@AutoWired

@AutoWired

JPA

JSF Don’t touch Spring specific

APIs yet

Spring beans

Migration Path






myapp.warSpring container

Servlet Container

Spring application

Spring beans

Spring beans

TX

TX

m

an

ag

er

man

ag

er

AO

PA

OP

OR

MO

RM

Java EE 6 application server

CDI / EJB container

myapp.war

CDI beans

Session beans

TX

man

ag

er

TX

man

ag

er

Secu

rity

Secu

rity

Inte

rcep

tors

Inte

rcep

tors

JPA

JPA

Java EE application

Java EE 6 application server

CDI / EJB container

myapp.warCDI beansSession beans

TX

man

ag

er

TX

man

ag

er

Secu

rity

Secu

rity

Inte

rcep

tors

Inte

rcep

tors

JPA

JPA

Spring containe

rSpring beans

Spring beans

TX

TX

m

an

ager

man

ager

AO

PA

OP

OR

MO

RM

Mixed

Run Spring within a Java EE containerpresentat

onlayer

Data / Integratio

nlayer

Spring beans

Tasks


businesslayer

JMS beans

@AutoWired

@AutoWired

JPA

JSF

Add Java EE code, keep old Spring code

presentaton

layer

Data / Integratio

nlayer

Spring beans

Tasks


businesslayer

JMS beans

@AutoWired

@AutoWired

JPA

JSF

EJB CDI

@Inject

@Inject

The Spring DAO

Spring configuration

JSF / CDI bean

Here we don’t want to know about Spring

Encapsulate Spring with CDI

Write a CDI extension that

bootstraps the Spring container

looks up Spring Beans in the Spring container and publish in CDI context

CDI extension example

Migration Path






Replace Spring entirelypresentat

onlayer

Data / Integratio

nlayer

Spring beans

Tasks


businesslayer

JMS beans

@AutoWired

@AutoWired

JPA

JSF

EJB CDI

@Inject

@Inject

Replace Spring entirelypresentat

onlayer

Data / Integratio

nlayer

EJB Timers

businesslayer

MDB

@AutoWired

@AutoWired

JPA

JSF

EJB CDI

@Inject

@Inject


The TX layer

Migrate Spring TX and DAOs to EJB

The TX manager is in the app server

An EJB is transactional by default

EJB has JPA integration

Come on, are you telling me EJBs are

cool now?You bet!

EJBs are just container managed POJOs

Just like Spring beans, but without the container configuration...

DAO

Spring

DAO configuration

The Java EE alternative

EJB

Dealing with Lazy Loading

Many Spring apps use the Open-EntityManager-In-View pattern

EJB has the Extended Persistence Context

more explicit and more powerful

LazyInitializationException

Fixing lazy loading

Keeps an EntityManager open as long a the bean exists

Template addict?

What if I’m hooked to JDBC Template?

Hmm, let’s start the old discussion about whether or not to use ORM

phase 1: denial

phase 2: eventually you will migrate ;-)

Using JDBC Template within

Java EECan be injected with simple Producer method

Possible because it is not relying on Spring container

some extra dependencies though

Template producer example

Migration Path






Removing dependencies

Our classpath just has to contain APIs, no framework classes

From ~40 dependencies to just 1

What about testing?

Spring has always been great at testing

DI makes unit testing possible

Spring test framework makes testing within the Spring container possible

Flexible configuration for multi-environment testing

How to test this?

Arquillian

Create a micro deployment using an API

Deploy to a real application server

Run tests in the server

Arquillian example

Is it all worth it?

Is there life after Spring?

We believe that there is always room for innovation

Ideally through Open Source

If it flies, bring it back to the spec!

There is more!

• 4-part article series on Jboss web site

• Step-by-step migration of Pet Clinic sample application

• http://www.howtojboss.com

http://www.howtojboss.com/

thank you

Documents

JAVA EE 6 Best Practices for Migrating Spring to WTF ?!?