EJB 3.2/JPA 2.1 Best Practices with Real-Life Examples - CON7535

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.

Transcript

1. © 2015 IBM Corporation
   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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2. © 2015 IBM Corporation
   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 Researcher
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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?
    NO
    

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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 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 AttributeConverterDatabaseType> 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.
    2. 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.
    3. 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
    ansgohar
    

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