Easy data-with-spring-data-jpa

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Java and Spring Data JPA: Easy SQL Data Access
Abstract
Presenter: Miya W. Longwe, MBA, MSE, Tech Lead, Staples, Inc, Framingham MA 01702
Accessing data repositories in various applications programming languages typically involves writing of tedious boilerplate lines of code. Some application development frameworks such as Spring have tried to make the experience more succinct by providing abstraction layers such as HibernateTemplate and JdbcTemplate, etc. Despite these APIs, the developers still spend a lot time writing repetitive code than concentrating on implementing business requirements. Developers at Spring, led by Oliver Gierke, introduced Spring Data JPA which “aims to significantly improve the implementation of data access layers by reducing the effort to the amount that's actually needed. As a developer you write your repository interfaces, including custom finder methods, and Spring will provide the implementation automatically”.
Spring Data JPA provides a powerful, out-of-the-box alternative to creating your own DAO framework. You declare custom repository operations on an interface, and the framework generates dynamic implementations (not code generation) automatically, based on conventions around method names. As part of the presentation, we'll also review a demo to look at Spring Java configuration (as opposed to XML configuration), and investigate the @Profile annotation – configuration details which may make life a bit easier in various ways when setting up unit testing of our repository classes, using out-of-the-box alternative to creating DAO framework, how to create custom repositories, pagination and support for custom queries among other features.

Presenter's Bio
Miya W. Longwe is a Senior Software Engineer and Tech Lead at Staples, Inc. where he is currently working on an initiative to re-platform the company’s ecommerce architecture to offer platform-driven, modular products that can be quickly customized, enhanced, and branded as needed.
Miya has been a software professional since 1997. His 16 years software development career includes working for large companies to small startups, building solutions for enterprises and consumers, working with a broad range of technologies.
Miya Longwe is a hands-on java developer. He believes that in order to be a relevant and effective software developer one needs to remain a deeply knowledgeable, up-to-date, and productive software developer. His research interests include model-driven engineering, domain specific languages, test driven development and project risk management.
Miya graduated from the University of Malawi (Lilongwe, Malawi) and has an MBA from the University of Wales Cardiff Business School (Wales, UK) and a Masters in Software Engineering from Brandeis University (MA, USA).
Occasionally, Miya can be spotted fishing the banks of the south shore (MA) with his two boys, William and Daniel.

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Easy data-with-spring-data-jpa

  1. 1. Easy Data with Spring-Data JPA Miya W. Longwe, Tech Lead, Staples Inc. January 07, 2014 Java Meetup Group, Cambridge, MA , USA
  2. 2. Agenda  Java DB Access Ordeal  Enter Spring-Data  Spring-Data JPA Features  Code Demo  Q and A
  3. 3. Java DB Access The Developer’s Holy Pilgrim!
  4. 4. Application Domain  Domain driven design has become a ubiquitous approach to tackle complex problem domains and build a rich object model.  Implementing a data access layer of an application has been cumbersome for quite a while.  Too much boilerplate code has to be written.  Code to execute simple queries as well as perform pagination, auditing, etc
  5. 5. Java DB Access – Accessor Interface public interface CustomerService { Customer findById(Long id); Customer save(Customer customer); List<Customer> findAll(); List<Customer> findAll(int page, int pageSize); ... }
  6. 6. Java DB Access – The Boilerplate Code /** * Plain JPA implementation of {@link CustomerService}. * * @author Miya W Longwe */ @Repository @Transactional(readOnly = true) public class CustomerServiceImpl implements CustomerService { @PersistenceContext private EntityManager em; @Override public Customer findById(Long id) { return em.find(Customer.class, id); } @Override public List<Customer> findAll() { return em.createQuery("select c from Customer c", Customer.class).getResultList(); } …… }
  7. 7. Java DB Access – The Story ● JPA handles mechanics of ORM ● The catch: – You are responsible for accessor boilerplate code ● Using direct JDBC? – More boilerplate code (think DAO layer) ● What about Spring support? – Makes things better (JdbcTemplate) – Spring-Data eases the pain further
  8. 8. Spring-Data to the Rescue!
  9. 9. Spring-Data  Uses the Repository abstraction for data access  Automation of data access boilerplate code  Reduces level of efforts for accessor code  Support for multiple data stores including– JPA– Key-Value, column, document, graph data stores(Redis, Mongo, Neo4j, HBase)– Hadoop / HDFS – Others
  10. 10. Spring-Data JPA Workflow  Define an Entity Class  Define a Repository interface with data accessor methods  Then see you gator!
  11. 11. Define Your Entity /** * An entity class which contains the information of a single person. * @author Miya W. Longwe */ @Entity @Table(name = "persons") public class Person { @Id @GeneratedValue(strategy = GenerationType.AUTO) private Long id; @Column(name = "creation_time", nullable = false) private Date creationTime; @Column(name = "first_name", nullable = false) private String firstName; @Column(name = "last_name", nullable = false) private String lastName; @Column(name = "modification_time", nullable = false) private Date modificationTime; ...}
  12. 12. Define The Repository Interface  You provide a Java interface  – Attach an entity type along with key type  – CRUD/data accessor method signatures  Spring-Data can automatically derive proper JPQL  In simpler cases, no additional code required  Queries are derived from method signatures
  13. 13. Repository Interface * Specifies methods used to obtain and modify person related information * which is stored in the database. * @author Miya W. Longwe */ public interface PersonRepository extends JpaRepository<Person, Long> { }
  14. 14. No More Boilerplate Code  It goes away (sort of) *  Spring-Data framework derives and attaches JPQL (or specified query) at load-time
  15. 15. Spring-Data Features
  16. 16. Provided Repositories  Spring-Data JPA provides two repositories  CrudRepository – Long list of standard CRUD operations provided – findOne(), findAll(), save(), delete(), exists(), etc  PagingAndSortingRepository – Derived from CrudRepository – Provides paginated repository access methods
  17. 17. Configure Spring Framework  Specify your repository locations for scanning  Spring will create proxy instances for repositories <?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http:/www.springframework.org/schema/beans" xmlns:jpa="http://www.springframework.org/schema/data/jpa" xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.1.xsd http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa-1.0.xsd http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.1.xsd"> <mvc:resources mapping="/static/**" location="/static/"/> <mvc:default-servlet-handler/> <!-- Configures Spring Data JPA and sets the base package of my DAOs. --> <jpa:repositories base-package="com.meetup.easydata.spring.datajpa.repository"/> </beans>
  18. 18. Spring-Data Query Generation  Derived from method signatures  Parses method names for attributes and keywords  Uses method parameters as query params public interface UserRepository extends CrudRepository<User, Long> { List<Customer> findByEmailAddressAndLastname(String emailAddress, String lastname); } Select c from Customer where c.emailAddress = ?1 and c.lastName = ?2
  19. 19. Spring-Data Method Name-to-JPQL Mapping Method Name Generated JPQL findByXxxAndYyy(aaa, bbb) ... where t.xxx = ?1 and t.yyy = ?2 findByXxxOrYyy(aaa, bbb) ... where t.xxx = ?1 or t.yyy = ?2 findByXxxStartingWith(a aa) ('%' appended to param value) findByXxxNot(aaa) ... where t.xxx <> ?1 findByXxxIn(Collection< E>aaa) ...where t.xxx in ?1 ---and many more!
  20. 20. Spring-Data Further Property Parsing Features -Traversal can reach into nested properties -Will do best effort using camelCase -You can delineate properties using “_” } @Entity public class User <Long> { private ZiCode zicode; --} } public interface UserRepository extends CrudRepository<User, Long>{ ... User findByAddress_ZipCode(ZipCode zipCode);
  21. 21. @Query – Use Your Own Query • You don't like the derived query or want to do something fancier? ● Use @Query notation to provide your own ● Support both JPQL or native SQL ● Still provides automatic proxy implementation public interface UserRepository extends CrudRepository<User, Long>{ ... @Query("select u from User u where u.firstname = ?1") List<User> findByFirstname(String firstname); @Query(value="SELECT FROM USERS WHERE EMAIL_ADDRESS = ?1" nativeQuery=true) User findByEmailAddress(String email); ...
  22. 22. @Query – Named Params • Spring-Data JPA will use position for parameter binding • You can also use named params instead interface UserRepository extends CrudRepository<User, Long>{ ... @Query("select u from User u where u.firstname = :name or u.lastname = :name") List<User> findByFirstnameOrLastname(@Param("name") String name); ... }
  23. 23. Result Pagination • Seamlessly provides support for result set pagination via Pageable Interface • Define repository method with Pageable • Call method with PageRequest class (or define your own) public interface ProductRepository extends CrudRepository<User, Long>{ ... Page<Product> findAll(Pageable pageable); ... } class ProductService { Pageable pageable = new PageRequest(1, 20); Page<Product> page = repository.findByDescriptionContaining(pageable); }
  24. 24. Custom Repositories • When Spring-Data JPA derived queries are not • enough or you need additional logic • Provide your own repository implementation • A bean that lives in Spring Context interface UserRepositoryCustom { List<User> myCustomBatchOperation(); } class UserRepositoryImpl implements UserRepositoryCustom { @PersistenceContext private EntityManager em; public List<User> myCustomBatchOperation() { CriteriaQuery<User> criteriaQuery = em.getCriteriaBuilder().createQuery(User.class); return em.createQuery(criteriaQuery).getResultList(); } }
  25. 25. Transaction Support • Repository classes are transactional by default • Reads are made readOnly • Other methods are @Transactional by default • Ability to override by providing your own @Transactional demarcation public interface UserRepository extends CrudRepository<User, Long>{ ... @Transactional(timeout=10) @Modifying @Query("update User u set u.firstname = ?1 where u.lastname = ?2") User fixFirstNameByLastName(String firstname, String lastname); ... }
  26. 26. Code Demo

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