When we use JPA API in a String Boot project by extending repository class with JpaRepository and use MySQL database instead of hibernate's H2 database, I wanted to know is there hibernate still involved behind the scenes or, is it that JPA works with MySQL?
From what I have researched, Hibernate is implementation of JPA but I can't find any reference how MySQL works with JPA?
Related
I am trying to understand various dependencies of spring boot.
I have come across three of them:
spring-boot-starter-data-rest
spring-boot-starter-data-jpa
spring-boot-starter-data-jdbc
I would like to know the difference between the three. Tried searching online documents, which say the three are almost related to spring data. how to resolve the confusion?
To add in here I have also found an another dependency
spring-boot-starter-web-services. I think it supports both SOAP and REST. Its just my assumption, I waiting for an explanation
spring-boot-starter-data-jpa is used to access your database with JPA (Java Persistence API)
spring-boot-starter-data-jdbc is used to access your data with jdbc (Java Database Connectivity)
the difference between JPA and JDBC is the level of abstraction. JDBC is more low level, JPA is more 'magic'
and spring-boot-starter-data-rest is used to provide Rest Endpoints on top of your Spring Data repositories.
To do this, you just annotate your spring data repository with a RepositoryRestResource annotation and direct Spring MVC creates the Restful endpoints.
#RepositoryRestResource(collectionResourceRel = "people", path = "people")
public interface PersonRepository extends PagingAndSortingRepository<Person, Long> {
List<Person> findByLastName(#Param("name") String name);
}
This is very handy if you do very CRUD like (Create, Read, Update, Delete) applications.
JPA means "Java Persistence API". It's for querying or saving data in relational databases using object-relational mapping.
REST means "REpresentational State Transfer". It's a style for creating web services that leverages HTTP verbs, a simpler alternative to SOAP.
JDBC starter uses the Spring JdbcTemplate to query or save data in relational databases without relying on object-relational mapping. You write SQL and ask the JdbcTemplate class to execute it in the database using JDBC.
I would say JPA and JDBC starters should be mutually exclusive: either one or the other.
You use REST only if you're writing web services. These may or may not query or persist data in a relational database. I would expect to see both the REST starter and a persistence starter in a pom if a REST service needed persistent data.
Three very different starters.
You ask why Spring Boot has a REST data starter parent that combines the two. In a word: convenience.
What is the default ORM provider for spring data if I don't mention about any ORM providers in my configurations?
Spring Data JPA is not a JPA provider. It is a library/framework that adds an extra layer of abstraction on the top of our JPA provider.
Hibernate is a JPA implementation, while Spring Data JPA is a JPA Data Access Abstraction. Spring Data offers a solution to GenericDao custom implementations. It can also generate JPA queries on your behalf through method name conventions.
With Spring Data, you may use Hibernate, Eclipse Link, or any other JPA provider
you should study this blog
is it possible to create database schema using spring boot with JPA in postgresql through java coding? like we are creating tables using spring boot with JPA.
Yes you can do. Please refer the Spring Documentation.
Database Initialization
I am new to Hibernate and Spring boot. I understand that hibernate is ORM tool so that you can map objects to database and just use save() to save obj into the database automatically. In Spring Boot, I would do something like
public interface CourseRepository extends CrudRepository<Course, String>{
}
and somehow I will get all the CRUD operations like save and findAll etc.
From another tutorial of hibernate, it says that session is required to save the object to the database. However, I don't see any form of sessionfactory or session being implemented in Spring boot and I am still able to do the save and findAll operations etc.
How is this happening and what relations does this have with hibernate?
Where exactly should I start to find out more about hibernate, stuff like #OneToMany and basically understand the details of the whole application to database operations in spring boot? Thanks
Spring Boot takes care of all the session management. Refer to this question for better understanding:
Spring Boot & Spring Data: how are Hibernate Sessions managed?
there are two things crudRepository and sessionFactory. try to find out difference between them and also try to read what is JPA and Hibernate.
I have a lot of JPA entities automatically created from a relational database schema.
Is there any way to generate also there corresponding Spring Data Repositories (Repository interfaces)?
You can use Spring Roo to create models and repositories by one command.
http://docs.spring.io/spring-roo/reference/html/intro.html
Wel, it's not for JPA, but I created a tool, EWA, for creating Repositories, Services and Models for Spring Boot + sql2o, a simple db driver, the fastest after pure JDBC.