Spring Boot is a popular Java web application framework that provides a range of features, including a CLI, embedded Tomcat, and auto-configuration. Spring Data is a sub-project of Spring that focuses on providing data access and persistence solutions for Java applications.
In this article, we'll take a look at how to use Spring Boot and Spring Data to access and persist data in a relational database. We'll also explore some of the features that make Spring Data a good choice for data access and persistence in Java applications.
Spring Boot can be configured to work with a variety of relational databases, including MySQL, PostgreSQL, and Oracle. In this section, we'll take a look at how to configure Spring Boot to work with a MySQL database.
First, we'll need to add the following dependency to our pom.xml
file:
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
Next, we'll need to configure some properties in our application.properties
file:
spring.datasource.url=jdbc:mysql://localhost:3306/mydatabase
spring.datasource.username=myusername
spring.datasource.password=mypassword
spring.jpa.database=MYSQL
spring.jpa.show-sql=true
spring.jpa.hibernate.ddl-auto=update
In the spring.datasource
properties, we're configuring the URL, username, and password for our MySQL database. In the spring.jpa
properties, we're configuring the database type (MySQL), telling Spring Boot to show SQL queries, and telling Hibernate to automatically update the database schema.
Spring Data makes it easy to access data in a relational database with Java. In this section, we'll take a look at how to use Spring Data to access data in a MySQL database.
First, we'll need to create a @Repository
interface for our data:
@Repository
public interface MyRepository extends JpaRepository<MyEntity, Long> {
}
The @Repository
annotation tells Spring that this is a repository for data. The JpaRepository
interface provides methods for accessing data in a relational database. The MyEntity
class is an entity class that represents a row in our database. The Long
type is the type of the primary key for our entity.
Next, we'll need to create an entity class:
@Entity
public class MyEntity {
@Id
@GeneratedValue
private Long id;
private String name;
// Getters and setters
}
The @Entity
annotation tells Spring that this is an entity class. The @Id
annotation tells Spring that the id
field is the primary key for the entity. The @GeneratedValue
annotation tells Spring that the id
field should be automatically generated by the database.
Now that we have our repository and entity classes set up, we can use them to access data in our database. For example, we can use the findAll()
method to find all entities in our database:
List<MyEntity> myEntities = myRepository.findAll();
We can also use the save()
method to save an entity to our database:
MyEntity myEntity = new MyEntity();
myEntity.setName("John Smith");
myRepository.save(myEntity);
In this article, we've looked at how to use Spring Boot and Spring Data to access and persist data in a relational database. We've also seen how Spring Data makes it easy to access data in a Java application.