Using JPA or JDBC in Micronaut

When building data-driven applications, Micronaut Data allows you to choose between:

JPA (Java Persistence API)
JDBC (Direct SQL Mapping)

Both approaches are fully supported by Micronaut Data, but they serve different use cases.
In this post, we’ll explore both options, their differences, pros/cons, and how to configure them.

🔍 What is JPA?

JPA (Java Persistence API) is the standard API for object-relational mapping (ORM) in Java.
It allows you to map Java objects (entities) to database tables and automatically handles SQL generation.

✅ Familiar if you’ve used Hibernate, Spring Data, Jakarta EE.
✅ Full ORM — relationships, lazy loading, cascading, etc.
✅ More abstraction, less SQL.

Micronaut supports JPA through its micronaut-data-jpa module.

🔍 What is JDBC in Micronaut Data?

JDBC (Java Database Connectivity) uses Micronaut’s micronaut-data-jdbc module for more direct mapping.

✅ Simple SQL mapping without full ORM.
✅ Fast compile-time query generation.
✅ Minimal runtime overhead.
✅ Excellent for microservices where complex ORM features aren’t needed.

Micronaut Data JDBC focuses on compile-time SQL generation — no heavy runtime proxies like Hibernate.

⚖ JPA vs JDBC: Quick Comparison

Feature	JPA	JDBC
Performance	Slower (runtime parsing)	Faster (compile-time SQL)
Complexity	Higher (lazy loading, proxies)	Lower
Learning Curve	Steeper	Easier
Relationships	Full ORM	Limited (manual handling)
Use case	Complex domains	Microservices, high-performance apps

🔧 Configuring JPA in Micronaut

Add Maven Dependencies

<groupId>io.micronaut.data</groupId>

<artifactId>micronaut-data-hibernate-jpa</artifactId>

</dependency>

<groupId>org.hibernate.orm</groupId>

<artifactId>hibernate-core</artifactId>

</dependency>

✅ Micronaut Data uses Hibernate under the hood when JPA is selected.

Sample JPA Entity

package com.kscodes.micronaut.school.entities;

import jakarta.persistence.*;

import java.time.LocalDate;

@Entity

@Table(name = "students")

public class Student {

@Id

@GeneratedValue(strategy = GenerationType.IDENTITY)

private Long id;

@Column(nullable = false)

private String name;

private LocalDate dateOfBirth;

private String email;

// Getters and Setters

}

✅ Uses standard JPA annotations from jakarta.persistence.

Repository Interface (same as before!)

package com.kscodes.micronaut.school.repositories;

import com.kscodes.micronaut.school.entities.Student;

import io.micronaut.data.annotation.Repository;

import io.micronaut.data.repository.CrudRepository;

@Repository

public interface StudentRepository extends CrudRepository<Student, Long> {

}

💡 Even with JPA, Micronaut generates repository code at compile-time.

Enable JPA in application.yml

jpa:

default:

properties:

hibernate:

hbm2ddl:

auto: update

✅ For production, you should disable hbm2ddl.auto and use migrations like Flyway or Liquibase.

🔧 Configuring JDBC in Micronaut

Add Maven Dependencies

<groupId>io.micronaut.data</groupId>

<artifactId>micronaut-data-jdbc</artifactId>

</dependency>

✅ No Hibernate required!

Sample JDBC Entity

package com.kscodes.micronaut.school.entities;

import io.micronaut.data.annotation.*;

import java.time.LocalDate;

@MappedEntity("students")

public class Student {

@Id

@GeneratedValue(GeneratedValue.Type.IDENTITY)

private Long id;

@Column(nullable = false)

private String name;

private LocalDate dateOfBirth;

private String email;

// Getters and Setters

}

✅ Uses @MappedEntity instead of @Entity.
✅ Mapping is much lighter.

Repository Interface (same!)

✅ Whether you use JPA or JDBC — repository code remains very similar.

Configure Datasource for JDBC (same as before)

datasources:

default:

url: jdbc:h2:mem:devDb;DB_CLOSE_DELAY=-1;DB_CLOSE_ON_EXIT=FALSE

username: sa

driverClassName: org.h2.Driver

dialect: H2

🧪 Which one should you choose?

If you need…	Use
Full ORM, relationships, cascading	JPA
Simpler, faster, lightweight mapping	JDBC
Large monolith enterprise systems	JPA
Modern microservices & cloud apps	JDBC

🐞 Common Errors

Error	Cause	Solution
Hibernate exceptions	Missing Hibernate dependency	Add micronaut-data-hibernate-jpa
Table not found	Auto-DLL disabled	Use Flyway/Liquibase or enable auto
Field mapping issues	Incorrect annotations	Use correct annotations for JPA vs JDBC

🌐 External References

✅ Summary

✅ Micronaut supports both JPA and JDBC.
✅ JDBC is lighter and faster.
✅ JPA is full ORM and more powerful for complex domains.
✅ Choose based on your project’s size and complexity.