Session ID: CON7535 Session Title: EJB 3.2/JPA 2.1 Best Practice with life examples Session Type: Conference Session Session Abstract: This session’s speaker, an architect, discusses lessons learned from using JPA and EJB to support a high-volume, high-performance applications. These best practices don't only involve JPA/EJB but also its integration with other Java EE 7 technologies. They also include coding best practices, testing and production practices. The presentation focuses primarily on some Key concepts such as persistence context, lazy loading, caching, flushing, dirty checking, transaction and connection demarcation. This is a fast-paced presentation with many code samples. Categories covered include configuration, JPA, concurrency, performance tuning, exception handling and many more.

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EJB 3.2/JPA 2.1 Best Practices with Real-Life Examples [CON7535]
EJB 3.2/JPA 2.1 Best Practices with
Real-Life Examples
[CON7535]
Ahmad Gohar, Architect
IBM Experienced IT-Specialist
Client Innovation Center (CIC)
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Ahmad (Nabil) Gohar
Architect & Technical Team Lead (9Y.)
Client Innovation Center CIC | IBM Egypt
IBM Certified Experienced IT Specialist
M.Sc. in Information System, FCI, Egypt
MIBA in Global Management, ESLSCA, France
OCEJPA, OCPWCD,OCPJP, OCP PL/SQL, MCP(s)
JAVA Community Process (JCP) Member
Blogger Author and Academic Researcher2

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JavaOne 2015 Keynote
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ENCRYPT STRING DATA
Entity
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Data Model
Oracle HR Employees Table
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The EncryptorBean
The EncryptorBean handles encryption but does not
know what’s being encrypted.
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Encryption Main requirements
Provide a transparent encryption that does not
affect the application,
Develop application and security/encryption by two
different teams/persons.
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1- Encryption Using Facade
Facade
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1- Encryption Using Facade
Persistence manager quietly handles your
encryption
Architecture demands a tight and unnecessary
binding between your persistence and security
designs.
You can’t touch one without also touching the other.
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2- JPA EntityListeners
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2- JPA EntityListeners
 A solution is JPA EntityListeners
 These are Listener classes that can provide methods called before or after database object
creation, deletion or modification.
– @PrePersist
– @PreUpdate
– @PreRemove
– @PostLoad
– @PostUpdate
– @PostRemove
 To keep a clean separation between the persistence and security layers the listener does
nothing but call a service that handles the encryption.
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3- Converter (AttributeConverter) @JPA 2.1
Attribute Converter provide a nice and easy way to
define a custom mapping between your property on
the entity and the database column.
The only thing that is needed is a class that
–implements the AttributeConverter interface
–annotated with @Converter.
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Converter (AttributeConverter)
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Converter Class

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Converter (AttributeConverter)
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JPA
Facade

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Entity Listeners or Attribute Converter?
Entity Listener Adv.
The entity listener can use
multiple attributes of the
entity during encryption.
So we can join multiple
attributes, encrypt them
and store the encrypted
data in one database field.
Entity Listener Drawbacks
Its implementation is
specific for an entity
More complex than the
implementation of a
Attribute Converter.
If we need to encrypt an
additional attribute, you
need to change the
implementation.
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Entity Listeners or Attribute Converter?
The Converter Adv.
Can be used to encrypt
any String attribute of any
entity.
By using the XML based
configuration to register
the converter to the entity
attribute, it requires no
change in the source code
of the application.
The Converter Drawbacks
The encrypted entity
attribute cannot be marked
as transient.
This might result in
vulnerabilities if the entity
gets written to the disk.
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Entity Listeners or Attribute Converter?
Both approaches have their pros and cons.
You have to decide which advantages and
disadvantages are more important to you.
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ENCRYPT OBJECT DATA
Entity
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BigDecimal Converter
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BigDecimal Converter
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Converter Class

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BigDecimal Converter
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JPA

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JAVA 8 DATE TIME API
JSR 310
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Java 8 Date Time API
 A date without a time-zone in the ISO-8601 calendar system, such as 2007-12-03.
 LocalDate is an immutable date-time object that represents a date.
 Other date fields, such as day-of-year, day-of-week and week-of-year, can also be
accessed.
 The ISO-8601 calendar system is the modern civil calendar system used today in most of
the world.
 However, any application that makes use of historical dates, and requires them to be
accurate will find the ISO-8601 approach unsuitable.
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Java 8 Date Time API
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Does JPA 2.1 support LocalDate and LocalDateTime?
The answer is simple,
JPA 2.1 was released before Java 8 and the Date and
Time API simply didn’t exist at that point in time.
Therefore the @Temporal annotation can only be applied
to attributes of type java.util.Date and java.util.Calendar.
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Why JPA not support LocalDate and LocalDateTime?
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HOW TO PERSIST
LOCALDATE AND
LOCALDATETIME WITH JPA
Entity
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How to persist LocalDate and LocalDateTime with JPA
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Converter Class

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How to persist LocalDate and LocalDateTime with JPA
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JPA

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Converting LocalDateTime
 The attribute converter for LocalDateTime is basically the same.
 You need to implement the AttributeConverter<LocalDateTime, Timestamp> interface and
the converter needs to be annotated with the @Converter annotation.
 Similar to the LocalDateConverter, the conversion between a LocalDateTime and an
java.sql.Timestamp is done with the conversion methods of Timestamp.
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LocalDate/LocalDateTime Conclusion
 JPA 2.1 was released before Java 8 and therefore doesn’t support the new Date and Time
API.
 If you want to use the new classes (in the right way), you need to define the conversion to
java.sql.Date and java.sql.Timestamp yourself.
 This can be easily done by implementing the AttributeConverter<EntityType, DatabaseType>
interface and annotating the class with @Converter(autoApply=true).
 By setting autoApply=true, the converter will be applied to all attributes of the EntityType and
no changes on the entity are required.
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DATA FETCHING STRATEGY
Entity
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Data fetching strategy
 EAGER – immediate
 LAZY – load only when needed
 Lazy is good for large objects with deep relationship hierarchies
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Lazy Loading Best Practices
 Lazy load fields and relationships that are not used frequently
 One-many/many-may relationships are lazy loaded by default
 Lazy load CLOB/BLOB if possible
 Accessing a LAZY relationship from a detached entity
– May get a null
– May get a previously cached value
– May get an exception
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WAYS TO INITIALIZE LAZY
RELATIONS
Entity | Data Fetching Strategy
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JPA
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Example

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1. Call a method on the mapped relation
Facade
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2. Fetch Join in JPQL
Facade
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JPA

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3. Fetch Join in Criteria API
Facade
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4. Named Entity Graph
JPA
Facade
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5. Dynamic Entity Graph
Facade
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5. Dynamic Entity Graph
Advantage
If we need lots of use case specific entity graphs, it might
be better to define the entity graph within the specific Java
code and to not add an additional annotation to the entity.
Avoids entities with dozens of annotations.
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Disadvantage
The dynamic entity graph requires more code and an
additional method to be reusable.

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5 ways to initialize lazy relations and when to use them
 Initializing a lazy relation via calling a method on a mapped relation causes an additional
query. This should be avoided for performance reasons.
 Fetch joins in JPQL statements reduce the number of queries to one but we might need a lot
of different queries.
 The Criteria API also supports fetch joins and we need specific code for each combination of
relations that shall be initialized.
 Named entity graphs are a good solution, if we will reuse the defined graph in our code.
 Dynamic entity graphs can be the better solution, if we need to define a use case specific
graph.
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QUERIES
Schemas and Queries
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Query
JPQL
JPA Criteria
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Query
JPA Criteria with Metamodel
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DEFINE NAMED QUERIES AT
RUNTIME
Schemas and Queries
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3 steps to define a named query at runtime
1. Create a Query.
– This can be done as a JPQL, native or criteria query.
– You can also define additional hints and settings for the query.
1. Find a name for your query that is unique within your persistence unit.
– If there is already a named query defined for the name, the query will be updated.
1. Use the Query and name to call the addNamedQuery(String name, Query query) method
on the EntityManagerFactory.
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Named Query at Runtime
Define the Named Query
Call the Named Query
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JPQL ENHANCEMENTS
Schemas and Queries
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JPQL enhancements
We can now use the keyword ON to define
additional join parameters
call database functions by using FUNCTION
downcast entities with TREAT.
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JPQL enhancement (FUNC)
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BULK UPDATES
Schemas and Queries
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Bulk Updates
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Bulk Updates
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STORED PROCEDURES IN JPA
Schemas and Queries
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4 different modes of parameters
 IN:
– for input parameters,
 OUT:
– for output parameters,
 INOUT:
– for parameters which are used for input and output and
 REF_CURSOR:
– for cursors on a result set .
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Oracle Stored Procedure
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Named Stored Procedure
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Named Stored Procedure
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Stored Procedure Query
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GENERATING DB SCHEMA
Schemas and Queries
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Generating DB Schema
 javax.persistence.schema-generation.database.action
 javax.persistence.schema-generation.scripts.action
 javax.persistence.schema-generation.create-source
 javax.persistence.schema-generation.drop-source
 javax.persistence.schema-generation.create-database-schemas
 javax.persistence.schema-generation.scripts.create-target
 javax.persistence.schema-generation.scripts.drop-target
 javax.persistence.database-product-name
 javax.persistence.database-major-version
 javax.persistence.database-minor-version
 javax.persistence.schema-generation.create-script-source
 javax.persistence.schema-generation.drop-script-source
 javax.persistence.schema-generation.connection
 javax.persistence.sql-load-script-source
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EJB LITE
EJB
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More features in EJB.Lite
Asynchronous session bean
Non-persistent EJB Timer service
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STATEFUL SESSION BEAN
EJB
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Stateful Session Bean Life Cycle
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Opt-out of passivation for stateful session bean
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TIMERSERVICE
EJB
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TimerService
 TimerService.getAllTimers
– a newly added convenience API that returns all timers in the same bean.
– This is only for displaying the list of timers as the timer can only be cancelled by its
owner.
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Painless Persistence
Invest in some JPA skills
Design your persistent objects
Create a services layer (DAOs are not sufficient)
Avoid cool but expensive features (e.g. Cascade)
and always work with the DBAs
Don't blindly do anything – always think before you
code!
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Wrap up
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Wrap up
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Encrypt String Data (AttributeConverter)
Encrypt Object Data (AttributeConverter)
Java 8 Date Time API (AttributeConverter)
Data fetching strategy
ways to initialize lazy relations(Named Entity Graph, Dynamic Entity
Graph)
Bulk Updates (Criteria Update)
stored procedures in JPA (Named Stored Procedure, Stored Procedure
Query)
define named queries at runtime
JPQL Enhancements

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Q. & A.
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https://about.me/ansgohar
http://ansgohar.blogspot.co.uk
https://eg.linkedin.com/in/ansgohar
https://www.facebook.com/ansgohar
https://twitter.com/ansgohar
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