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

Ahmad Gohar
October 28, 2015

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.

Ahmad Gohar

October 28, 2015

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  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) 1
  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 2
  3. © 2015 IBM Corporation Encryption Main requirements Provide a transparent

    encryption that does not affect the application, Develop application and security/encryption by two different teams/persons. 10
  4. © 2015 IBM Corporation 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. 12
  5. © 2015 IBM Corporation 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. 14
  6. © 2015 IBM Corporation 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. 15
  7. © 2015 IBM Corporation 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. 18
  8. © 2015 IBM Corporation 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. 19
  9. © 2015 IBM Corporation 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. 20
  10. © 2015 IBM Corporation 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. 26
  11. © 2015 IBM Corporation 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. 28 Why JPA not support LocalDate and LocalDateTime? NO
  12. © 2015 IBM Corporation 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. 32
  13. © 2015 IBM Corporation 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. 33
  14. © 2015 IBM Corporation Data fetching strategy  EAGER –

    immediate  LAZY – load only when needed  Lazy is good for large objects with deep relationship hierarchies 35
  15. © 2015 IBM Corporation 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 36
  16. © 2015 IBM Corporation 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. 44 Disadvantage The dynamic entity graph requires more code and an additional method to be reusable.
  17. © 2015 IBM Corporation 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. 45
  18. © 2015 IBM Corporation 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. 50
  19. © 2015 IBM Corporation Named Query at Runtime Define the

    Named Query Call the Named Query 51
  20. © 2015 IBM Corporation JPQL enhancements We can now use

    the keyword ON to define additional join parameters call database functions by using FUNCTION downcast entities with TREAT. 53
  21. © 2015 IBM Corporation 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 . 59
  22. © 2015 IBM Corporation 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 65
  23. © 2015 IBM Corporation 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. 72
  24. © 2015 IBM Corporation 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! 73
  25. © 2015 IBM Corporation Wrap up 75 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
  26. © 2015 IBM Corporation Q. & A. 76 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