Spring Data JPA presentation
 Singapore Spring User group March 10th 2015 Cedric Arnoult carnoult@palo-it.com

2 What are we going to talk about ? JPA Spring Data JPA Demo Spring Data JPA in our Project Non JPA era Q&A Pros and cons How does it work

3 Non JPA era   JDBC : Lots of boilerplate code   Connection   Open   Close   Statement   Create   ResultSet   Loop through   POJO mapping   Lots and lots of try catch, including catch in the try or the finally (don’t forget the finally !!!)   Spring JDBC templates   Less code   Still had to go through ResultSet

4 JPA   What is it ?   Standard way to access data layer providing a JPA provider   Hibernate   EclipseLink   OpenJPA   …   JPA Query language (JPQL)   Focus on mappings and relationships   What is it not ?   Adressing boilerplate code   getters and setters on your entities   EntityManagerFactory.getTransaction.begin(), persist(), commit() and close()   Lots of try ctach …

5 Spring Data JPA   What is it not ?   a JPA provider   a big huge thing with lots of things to learn   What is it ?   A promise : a way to improve the implementation of your data access layer, writing less code.   A project built on top of Spring Data.   Spring Data MongoDB   Spring Data Rest   Spring for Hadoop   …   What do you need ?   2 jars :   spring-data-jpa (latest version is 1.7.2-RELEASE)   spring-data-commons (latest version is 1.8.2-RELEASE)   Spring   JPA Entities and a JPA provider Introduction

6 Spring Data JPA   Key is : org.springframework.data.jpa.JpaRepository   One interface to extend :   It will bring to you :   Every basic CRUD methods covered at once   Even the not so basic ones   Sorting   Pagination   Lots of helpers based on reflection   Yes, you can still have custom queries One magic line of code

7 Demo   Demo time

8 How does it work   Proxy generated at bootstrap time   Scans your Spring configuration for your repositories   Relies heavily on Spring Data   JpaRepository extends PagingAndSortingRepository   PagingAndSortingRepository extends CrudRepository   CrudRepository extends Repository   SimpleJpaRepository is the default implementation of JpaRepository It’s not magical … but almost

9 Pros and cons   Pros   All basic queries are done for you   Abstraction allows you to change your relation model quite easily   Pagination and sorting work out of the box   Custom queries with @Query are validated at bootstrap time   You cannot go live with a query that is grammatically wrong   Cons   Don’t forget about Spring Data if you don’t want to get tied up with JPA   You might want to consider QueryDsl : Domain Specific Language. A new way way to do your queries

10 Spring Data JPA in our Project   Forget the boilerplate code   Learning curve is almost inexistant   Easy   Fast   Helped us to structure the code   1 entity = 1 repository   Coding standards (‘findxxx’ methods) ?   Performances are JPA performances   Hand made repositories are still possible   Still had to go out of JPA for 2 specific repositories   Did not use reflection based helpers   Less tests   All CRUD methods

11 Q&A   Spring data : http://projects.spring.io/spring-data/   Spring data JPA : http://projects.spring.io/spring-data-jpa/   Contact me cedric.arnoult@gmail.com   carnoult@palo-it.com