Spring Boot JPA

Spring Boot JPA
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Written by Sagar RabidasJanuary 6, 2022
11 min read
Spring
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Techiio-author
Sagar Rabidas

Software Developer

In this blog, we will discuss Spring Boot JPA.

Spring Boot:-

Spring Boot is a java-based framework used to create spring programs with the assist of microservices. It's far an open-source framework that provides bendy XML configurations, database transactions, robust batch processing, at ease management of relaxation services and endpoints, and easy workflow in less time than other java frameworks to be had within the marketplace presently. The various roles in the spring boot java framework are senior software engineer, spring java or software developer, and tech lead or architect in spring, while the titles can be modified from corporation to organization.

Spring Boot JPA:-

In spring boot we have JPA which makes the mapping of Java objects to the relational database. Through using it, we can carry out such a lot of operations on the database and get the preferred result we want. Spring boot framework gives us starter JPA dependency which incorporates all the required things, through the assist of this we can capable of performing and hook up with the database without problems. Jpa is a fixed of interfaces that follow the form technique which stands for item-relation mapping, by using the help of JPA, we can persist and get entry to the statistics or java object between the application and relational database. Because the database is a completely crucial part in terms of the garage of information and performing the transaction on those facts. Inside the coming phase of the academic, we will see how we can configure the JPA in the spring boot application to engage with the relation database and notice the usage as nicely for better understating.

Syntax:

As we know that to access the JPA we need to make some configuration in our application, the most command used annotation in spring boot is mention below, it is a basic configuration that we need, let’s take a closer look at the syntax for better understating to see below;

@SpringBootApplication
@EnableJpaRepositories
public class name_Application{}

As you can see we have used @EnableJpaRepositories to enable the JPA use inside the project. Also, we will have to look at the practice syntax to make use of JPA in, see below;

e.g. :

@SpringBootApplication
@EnableJpaRepositories
public class DemoApplication{}

In the coming section of the tutorial, we will what are the other configurations which need to in place in order to run the spring boot application in JPA easily and without error.

How Spring boot JPA works?

As we already recognize that for you to make the JPA paintings, we have to make some configurations additionally we want to add the dependency as properly. Jpa is essentially used to have the interplay between the java training and the database. Using the use of this, we can shop the values inside the database and fetch them whilst needed. First, let’s start with the lifecycle of the JPA by the steps which are described below;

  • NULL: First the object is in the null state, which means it is not associate with entityManager, Reference see below code:

e.g. :

Demo demo = null;
  • NEW: This is the second stage for the JPA object when we create the object using the new operator, but still entityManager does not exist.

e.g:

Demo demo = new Demo();
  • Managed: In this stage, the object we have created will be managed by the entityManager, so we will do some coding to register it inside the entityManager, by using the following code;

e.g.:

entityManager.getTransaction().begin();
Demo demo = new Demo();
entityManager.persist(demo);
entityManager.getTransaction().commit();

Here we have configured our object to entityManager now the entityManager will manage the object for us.

  • Detached: This state detaches means to remove the object from the entityManager. For reference see below;

e.g. :

entityManager.detach(demo);
  • Remove: This stage will help us to remove the object from the database.

e.g.:

entityManager.removed(myObject);

Examples

In this example, we will see the saving of a simple object inside the database. For that we have created the entity, service, repository to store the object, also we have added the dependency inside the pom.xml as well.

Example:

  • Add the below dependency also while creating the JPA example: without his, we will not be able to use the JPA features inside our application so it is required. You can directly type this name in the spring initializer and it will add this dependency for you.

e.g:

<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
  • Create the entity class like below; this will be the entity class that is going to store in the db., also later we can perform many operations on it like, fetch, delete, update, etc. based on the requirement.
@Entity
@Table(name = "STUDENT")
public class Student implements Serializable {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "ID")
private Long id;
@Column(name = "name")
private String name;
@Column(name = "city")
private String city;
}
  • now create the JPA repository to save the student object inside it, this is an interface and very important because through this only all the transactions will take place. @Repository annotation is required here, so we can autowired it later to make use of it.

e.g.:

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Modifying;
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.query.Param;
import org.springframework.stereotype.Repository;
import java. time.LocalDateTime;
import java.util.List;
@Repository
public interface StudentRepository extends JpaRepository<Student, String> {
}
  • Now one method inside the service class and auto wired the repository inside it to call the JPA methods to save the object.

e.g.:

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import java. time.LocalDateTime;
import java.util.List;
@Service
public class StudentService {
@Autowired
private StudentRepository studentRepository;
public void create(Student student){
studentRepository.save(student);
}
}
  • Now final step to make the configuration work, in the main application class of the project see below for reference;

e.g.:

package com. test.Traders;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.web.client.RestTemplate;
@SpringBootApplication
@EnableJpaRepositories
public class StudentApplication{
public static void main(String[] args){
}SpringApplication.run(StudentApplication.class, args);
}
  • Now run the above code and you will see below output; if the JPA is configured properly in the application and try to save object using any rest client, for that ad the controller as well, with a simple endpoint.

Conclusion

JPA is very easy to use and handle because spring boot makes this simple for us. We just need to do the little configuration after that we can use it, to store and retrieve our entity object from the database, we can follow the above steps to make this work in the spring boot application.

Spring
Spring Boot
Sprin Boot JPA
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