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
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2. Agenda
Motivation
Data recovery strategies
Lazy vs Eager
Cache
Web UI Design Strategies
Conversation Scope
View Helper + Persistence Service
Lazy UI Components
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3. Objective
“Present some tips and tricks on web
application development with JSF, Ajax,
and JPA”
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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!
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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.
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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.
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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!
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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.
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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.
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11. Cache
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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.
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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.
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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!
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16. Old Solution
OpenSessionInViewFilter Design Pattern;
New problems!
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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!
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18. Web 1.0
Request-oriented web applications;
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19. Web 2.0
AJAX-oriented web applications;
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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);
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21. Web UI Strategies
Tip: Store the persistence context into the view
scope or conversation scope;
The EntityManager remains open for a specified time;
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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.
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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).
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24. Web UI Strategies
Tip: Use UI Components that supports “lazy
loading” via Ajax;
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25. Web UI Strategies
Tip: Use UI Components that supports “lazy
loading” via Ajax;
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26. Web UI Strategies
Tip: Use UI Components that supports “lazy
loading” via Ajax;
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27. Sample Application
The tips and tricks are demonstrated by a sample
application;
It is avaliable to donwload at:
http://sourceforge.net/projects/j1catalogproto2/
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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
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