Introduction to Spring Data

Spring Data JPA is a separate project within Spring Data ecosystem to enable you connect with persistent stores(SQL and NoSQL).

spring-data

spring-data-abstraction

Spring DATA JPA (Java Persistence API)

Spring DATA JPA Features

  • Support for Querydsl to create type-safe JPA queries
  • Validation of @Query annotated queries at bootstrap time.
  • @EnableJpaRepositories
  • Advance Features
    • Extending and adding custom queries with JPQL
    • Query Domain Specific Language (Query DSL)
    • Defining custom methods (low-level coding)

Adding JPA

  • @Repository
  • Extends JpaRepository<MyEntity, Long>
  • List findByBestCategory(Boolean bestCategory), where bestCategory is a field(column)
public interface EmployeeRepository extends JPARepositoty<Employee, Integer>{
    // findAll()
    // findById()
    // save()
    // deleteById()
}

ORM(Object Relational Mapping)

  • Map Entity classes into relational mapping.
  • ORM framework does the query, transaction and mapping.
  • JPA is specification to use ORM.

orm

pom.xml

  • Hibernate-core
  • Hibernate entity manager

application.properties

  • Datasource
  • Hibernate.ddl-auto=update

Create POJO

  • @Entity, @TableName, @MappedSuperClass
  • @Column, @Id,

@EntityScan(basePackages={“a”,”b”})

@EntityScan vs @ComponentScan

Spring Data Rest

  • spring-data-rest
  • scans all JPARepositories, provides all basic crud features.
  • exposes REST api for each entity type for your JPARepository.
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-data-rest</artifactId>
</dependency>
  • Spring data rest endpoints are HATEOAS compliant
    • HATEOAS - Hypermedia As the Engine of Application State
  • Hypermedia driven sites provide information to access REST interfaces.
    • Think of it as metadata for REST data.
  • HATEOAS uses HAL (Hypertext Application Language) data format.
  • For a collection, metadata includes page size, total elements, pages etc.
  • Advance Features
    • Pagination, sorting and searching
    • Extending and adding custom queries with JPQL
    • Query Domain Specific Language (Query DSL)
@RepositoryRestResource(path="members")
public interface EmployeeRepository extends JPARepositoty<Employee, Integer>{
    // findAll()
    // findById()
    // save()
    // deleteById()
}

spring.data.rest.base-path=/base
spring.data.rest.default-page-size=10
spring.data.rest.max-page-size=50

http://localhost:8080/employees?sort=lastname,firstname,asc