Performance Tips and Tricks: Java EE, Java Persistence API and JavaServer Faces
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The document provides tips and tricks for developing web applications using JavaServer Faces (JSF), Java Persistence API (JPA), and Ajax. It discusses strategies for lazy vs eager data loading, caching, and web UI design. Specifically, it recommends using the view scope or conversation scope to store the persistence context and avoid lazy loading exceptions. It also suggests integrating view helpers with persistence services and using UI components that support lazy loading via Ajax.
Performance Tips and Tricks: Java EE, Java Persistence API and JavaServer Faces
- 1. Performance Tips and Tricks: Java EE, Java Persistence API, and JavaServer Faces Alberto Lemos (Dr. Spock) Danival Taffarel Calegari Senior Software Architect MATERA Systems Architect Globalcode Instructor Globalcode Instructor Globalcode – Open4education
- 2. Agenda Motivation Data recovery strategies Lazy vs Eager Cache Web UI Design Strategies Conversation Scope View Helper + Persistence Service Lazy UI Components Globalcode – Open4education
- 3. Objective “Present some tips and tricks on web application development with JSF, Ajax, and JPA” Globalcode – Open4education
- 4. Motivation JavaServer Faces (JSF) is a paradigm change in Web development with Java EE; It establishes a model for web UI components. JSF evolved! JSF 1.x (without AJAX) => Ineffective event oriented JSF 1.x + AJAX lib => Event oriented JSF 2.x => Event oriented It's necessary to evolve the development techniques on presentation and persistence layers! Globalcode – Open4education
- 5. Agenda Motivation Data recovery strategies Lazy vs Eager Cache Web UI Design Strategies Conversation Scope View Helper + Persistence Service Lazy UI Components Globalcode – Open4education
- 6. Lazy vs Eager Strategies to handle the entity relationships; Lazy: it fetches data on demand; Eager: it always fetches data. Globalcode – Open4education
- 7. Lazy vs Eager Tip: JPA allows for a change from lazy to eager using the JP-QL; select distinct c from Categoria c join fetch c.produtos It runs only one SELECT in the database; Join fetch solves the N+1 problem; Distinct should be used to avoid duplicated results; Note: this may cause problems with database pagination. Globalcode – Open4education
- 8. Lazy vs Eager Tip: Try to paginate in database using lazy strategy; Use the setFirstResult and setMaxResults methods by Query. The JPA provider will use native database commands to limit the query results; Beware: join fetch for 1:N relationships causes performance and memory problems. WARN: firstResult/maxResults specified with collection fetch; applying in memory! Globalcode – Open4education
- 9. Lazy vs Eager Tip: Try to use eager whenever bulk processing data; One common situation is report generation. Be careful with memory use; Do a previous query to get the ids and limit the results with an in clause; Use the clear method from EntityManager to remove processed objects from memory. Globalcode – Open4education
- 10. Cache First level cache While the EntityManager is open, it maitains the references for all objects loaded by it; This cache is erased when the clear method is called. Second level cache Maintains object references per EntityManagerFactory; It is a per-application cache. Globalcode – Open4education
- 11. Cache Globalcode – Open4education
- 12. Cache Trick: By loading related entities into first level cache before the main query, performance will be greatly improved. It can only work with N:1 relationships for entities with a small number of instances. Example: Fetching products with any filter. If there are 200 categories, the lazy strategy should run 200 queries on the category table; Execute a “select c from Category c” before querying for products. Globalcode – Open4education
- 13. Cache Tip: Use second level cache to save memory and to improve performance; Choose non-frequent altered entities; If an external application changes the database, data in the second level cache will become outdated. Apply a time limit for data expiration. Globalcode – Open4education
- 14. Agenda Motivation Data recovery strategies Lazy vs Eager Cache Web UI Design Strategies Conversation Scope View Helper + Persistence Service Lazy UI Components Globalcode – Open4education
- 15. The Problem DAO + JDBC => open/close connection; DAO + Persistence Context => open/close session; LazyInitializationException! Globalcode – Open4education
- 16. Old Solution OpenSessionInViewFilter Design Pattern; New problems! Globalcode – Open4education
- 17. New Problems OpenSessionInViewFilter Design Pattern; 1st REQUEST 2nd REQUEST Nth REQUEST Each request uses a different persistence context; Session scoped entities can throw LazyInitializationException! Globalcode – Open4education
- 18. Web 1.0 Request-oriented web applications; Globalcode – Open4education
- 19. Web 2.0 AJAX-oriented web applications; Globalcode – Open4education
- 20. Web UI Strategies Tip: Use the view and conversation scopes; Avoid to use the session scope for objects with short lifetime; Usually the lifetime is managed by the container through settings (Annotations or XML); Globalcode – Open4education
- 21. Web UI Strategies Tip: Store the persistence context into the view scope or conversation scope; The EntityManager remains open for a specified time; Globalcode – Open4education
- 22. Web UI Strategies Tip: Store the persistence context into the view scope or conversation scope; The EntityManager remains open for a specified time; Enables the 1st level cache; Prevents the LazyInitializationException errors; Enables paging in the presentation tier Integrated with the persistence tier; Attention: The 1st level cache can increase for a long term conversation scope. Globalcode – Open4education
- 23. Web UI Strategies Tip: Integrate the View Helper (pattern) with the persistence service (JPA); Implement a List (from Collections API) that receives a Query object (from JPA); Implement a DataModel (from JSF API) that receives a Query object; Implement an ExtendedTableDataModel (from Richfaces API) that receives an EntityManager object; Pagination: Use setFirtResult() and setMaxResults(). Be careful with eager fetching! Filter and order by: Use CriteriaBuilder object (from JPA). Globalcode – Open4education
- 24. Web UI Strategies Tip: Use UI Components that supports “lazy loading” via Ajax; Globalcode – Open4education
- 25. Web UI Strategies Tip: Use UI Components that supports “lazy loading” via Ajax; Globalcode – Open4education
- 26. Web UI Strategies Tip: Use UI Components that supports “lazy loading” via Ajax; Globalcode – Open4education
- 27. Sample Application The tips and tricks are demonstrated by a sample application; It is avaliable to donwload at: http://sourceforge.net/projects/j1catalogproto2/ Globalcode – Open4education
- 28. Thank you! Alberto Lemos (Dr. Spock) Danival Taffarel Calegari http://www.globalcode.com.br/ http://www.matera.com/ spock@globalcode.com.br danival@globalcode.com.br http://twitter.com/drspockbr http://twitter.com/danivaltc Globalcode – Open4education