In Memory

micronaut:
  application:
    name: backend
datasources:
  default:
    url:             jdbc:h2:mem:devDb;LOCK_TIMEOUT=10000;DB_CLOSE_ON_EXIT=FALSE
    username:        sa
    password:        ""
    driverClassName: org.h2.Driver
    schema-generate: CREATE_DROP
    dialect:         H2
netty:
  default:
    allocator:
      max-order: 3

MYSQL

example yml for connecting locally to mysql db

micronaut:
  server:
    port: 8082
  application:
    name: crudData
datasources:
  default:
    url:             jdbc:mysql://localhost:3306/micro_person
    username:        root
    password:        pw123
    driverClassName: com.mysql.cj.jdbc.Driver
    db-type:         mysql
    schema-generate: CREATE_DROP
    dialect:         MYSQL
netty:
  default:
    allocator:
      max-order: 3
#vertx:
#  mysql:
#    client:
#      port: 3306
#      host: localhost
#      database: micro_person
#      user: root
#      password: root
#      maxSize: 5

Hibernate

Hibernate uses a proxy object to implement lazy loading with a default implementation generating a proxy during the runtime.
This has a few disadvantages:
Runtime class generation can affect startup and runtime performance
Environments like GraalVM don’t support it

If you wish to use lazy entity associations and avoid runtime proxies you can enable compile-time proxies:

jpa:
  default:
    compile-time-hibernate-proxies: true

The entity Owner needs to be annotated with @GenerateProxy to have a proxy generated and the compile-time.

@Entity
@GenerateProxy
public class Owner {
    //...
}

Joins

@Repository
public interface ProductRepository extends CrudRepository<Product, Long>, JpaSpecificationExecutor<Product> {
    @Join(value = "manufacturer", type = Join.Type.FETCH)
        // 
    List<Product> list();
}

JPA Entity Graphs

@EntityGraph(attributePaths = {"manufacturer", "title"})
    // 
List<Product> findAll();

Hibernate schema generation

The hibernate.hbm2ddl.auto configuration property is used to customize the Hibernate database schema generation process, and it can take the following values:

none – This option disables the hbm2ddl.auto tool, so Hibernate is not going to take any action for managing the underlying database schema.
create-only – This option instructs Hibernate to generate the database schema from the entity model.
drop – This option instructs Hibernate to drop the database schema using the entity model as a reference for the DDL DROP statements.
create – This option instructs Hibernate to drop the database schema and recreate it afterward using the entity model as a reference.
create-drop – This option instructs Hibernate to drop the database schema and recreate it afterward using the entity model as a reference.
validate – This option instructs Hibernate to validate the underlying database schema against the entity mappings.
update – This option instructs Hibernate to update the database schema by comparing the existing schema with the entity mappings and generate the
appropriate schema migration scripts.

Reactive Hibernate

micronaut:
  server:
    port: 8082
  router:
    versioning:
      enabled: true
  application:
    name: hibernate
#datasources:
#  default:
#    url: jdbc:mysql://localhost:3306/ssi
#    username: root
#    password: root
#    dialect: MYSQL
#    driverClassName: com.mysql.cj.jdbc.Driver
#    db-type: mysql
#    schema-generate: none
jpa:
  default:
    reactive:                       true
    compile-time-hibernate-proxies: true
    entity-scan:
      packages:
        - "com.ssi.integration"
        - "com.ssi.result"
        - "com.ssi.request"
        - "com.ssi.Enums"
    properties:
      hibernate:
        show-sql: true
        hbm2ddl:
          auto: update
        connection:
          db-type:  mysql
          url:      jdbc:mysql://localhost:3306/ssi
          username: root
          password: root
netty:
  default:
    allocator:
      max-order: 3

DB Migration

Liquibase

yml

liquibase:
  enabled: true
  datasources:
    default:
      change-log: "classpath:db/liquibase-changelog.xml"
endpoints:
  liquibase:
    enabled:   true
    sensitive: false

changelog

<?xml version="1.0" encoding="UTF-8"?>
<databaseChangeLog
        xmlns="http://www.liquibase.org/xml/ns/dbchangelog"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://www.liquibase.org/xml/ns/dbchangelog http://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-3.1.xsd">

    <include file="changelog/01-create-person.xml"
             relativeToChangelogFile="true"/>

</databaseChangeLog>

db change file

<?xml version="1.0" encoding="UTF-8"?>
<databaseChangeLog
        xmlns="http://www.liquibase.org/xml/ns/dbchangelog"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://www.liquibase.org/xml/ns/dbchangelog http://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-3.1.xsd">

    <changeSet id="01" author="sdelamo">

        <createTable tableName="person"
                     remarks="A table to contain persons">

            <column name="id" type="BIGINT" autoIncrement='true'>
                <constraints nullable="false"
                             unique="true"
                             primaryKey="true"
                             primaryKeyName="personPK"/>
            </column>

            <column name="version" type="BIGINT">
                <constraints nullable="false"/>
            </column>

            <column name="first_name" type="VARCHAR(55)">
                <constraints nullable="false"/>
            </column>

            <column name="last_name" type="VARCHAR(55)">
                <constraints nullable="false"/>
            </column>

        </createTable>

    </changeSet>

</databaseChangeLog>