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JAVA EE 6

Best Practices for Migrating Spring to. JAVA EE 6. 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

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JAVA EE 6

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

  2. Bert Ertman Fellow at Luminis in the Netherlands JUG Leader for NLJUG and a Java Champion

  3. 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?

  4. 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...

  5. Why migrate? • Spring is proprietary technology • Upgrading from old school Spring requires a lot of work anyway • Why not take it to the standard?

  6. Scenario A

  7. But now we want this

  8. Let’s get a couple of misunderstanding out of the way first...

  9. 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

  10. But I need Dependency Injection • Java EE 6 introduced CDI • More powerful, contextual DI model • Makes the platform extensible in a standard way

  11. 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?

  12. Do I need heavy tooling?

  13. Capabilities comparison * Not part of the Java EE specification

  14. It can all be done using plain vanilla light weight Java EE

  15. rm -Rf spring* ?

  16. Sure it would be fun! realistic?

  17. Typical old school Spring app • lots of complex XML, no annotations • old / outdated ORM solution • (JDBC Templates, Kodo, Toplink etc.)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.)

  18. Migration Path • Upgrade Spring version • Replace old frameworks (ORM, web framework) within Spring • Run Spring and Java EE container side by side • Replace Spring entirely • Remove Spring container

  19. Migration Path • Upgrade Spring version • Replace old frameworks (ORM, web framework) within Spring • Run Spring and Java EE container side by side • Replace Spring entirely • Remove Spring container

  20. Upgrade Spring version • Upgrade Spring runtime (replace JAR files) • No code / configuration changes

  21. Migration Path • Upgrade Spring version • Replace old frameworks (ORM, web framework) within Spring • Add Java EE code, keep old Spring code • Replace Spring entirely • Remove Spring container

  22. Don’t touch Spring specific APIs yet Web MVC Tasks Spring JDBC Templates Kodo JMS beans JPA JSF Spring beans Replace old frameworks within Spring presentaton layer @AutoWired business layer @AutoWired @AutoWired Data / Integration layer

  23. Migration Path • Upgrade Spring version • Replace old frameworks (ORM, web framework) within Spring • Add Java EE code, keep old Spring code • Replace Spring entirely • Remove Spring container

  24. TX manager AOP ORM Spring application Servlet Container myapp.war Spring container Spring beans Spring beans

  25. Interceptors JPA TX manager Security Java EE application Java EE 6 application server CDI / EJB container myapp.war CDI beans Session beans

  26. Spring container TX manager ORM AOP Spring beans Spring beans Interceptors JPA TX manager Security Mixed Java EE 6 application server CDI / EJB container myapp.war CDI beans Session beans

  27. Spring beans Tasks Spring JDBC Templates JMS beans JPA JSF Run Spring within a Java EE container presentaton layer @AutoWired business layer @AutoWired Data / Integration layer

  28. Spring beans Tasks Spring JDBC Templates JMS beans JPA JSF EJB CDI Add Java EE code, keep old Spring code presentaton layer @AutoWired @Inject business layer @Inject @AutoWired Data / Integration layer

  29. The Spring DAO

  30. Spring configuration

  31. JSF / CDI bean Here we don’t want to know about Spring

  32. 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

  33. CDI extension example

  34. Migration Path • Upgrade Spring version • Replace old frameworks (ORM, web framework) within Spring • Add Java EE code, keep old Spring code • Replace Spring entirely • Remove Spring container

  35. Spring beans Tasks Spring JDBC Templates JMS beans JPA JSF EJB CDI Replace Spring entirely presentaton layer @AutoWired @Inject business layer @Inject @AutoWired Data / Integration layer

  36. EJB Timers MDB JPA JSF EJB CDI Spring JDBC Templates Replace Spring entirely presentaton layer @AutoWired @Inject business layer @Inject @AutoWired Data / Integration layer

  37. 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

  38. 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...

  39. DAO Spring

  40. DAO configuration

  41. The Java EE alternative EJB

  42. 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

  43. LazyInitializationException

  44. Fixing lazy loading • Keeps an EntityManager open as long a the bean exists

  45. 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 ;-)

  46. Using JDBC Template within Java EE • Can be injected with simple Producer method • Possible because it is not relying on Spring container • some extra dependencies though

  47. Template producer example

  48. Migration Path • Upgrade Spring version • Replace old frameworks (ORM, web framework) within Spring • Add Java EE code, keep old Spring code • Replace Spring entirely • Remove Spring container

  49. Removing dependencies • Our classpath just has to contain APIs, no framework classes • From ~40 dependencies to just 1

  50. 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

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