Learn to configure hibernate/JPA support in Spring Boot2 applications, along with creating entity classes and extending inbuilt JpaRepository
interfaces.
1. Maven Dependencies
In this example, we are using maven to add runtime jars in project. If you are using gradle then please find related dependencies.
<? xml version = "1.0" encoding = "UTF-8" ?> xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 < modelVersion >4.0.0</ modelVersion > < parent > < groupId >org.springframework.boot</ groupId > < artifactId >spring-boot-starter-parent</ artifactId > < version >2.1.5.RELEASE</ version > < relativePath /> <!-- lookup parent from repository --> </ parent > < groupId >com.howtodoinjava.demo</ groupId > < artifactId >SpringBoot2Demo</ artifactId > < version >0.0.1-SNAPSHOT</ version > < name >SpringBoot2Demo</ name > < description >Demo project for Spring Boot</ description > < properties > < java.version >1.8</ java.version > </ properties > < dependencies > < dependency > < groupId >org.springframework.boot</ groupId > < artifactId >spring-boot-starter-web</ artifactId > </ dependency > < dependency > < groupId >org.springframework.boot</ groupId > < artifactId >spring-boot-starter-data-jpa</ artifactId > </ dependency > < dependency > < groupId >com.h2database</ groupId > < artifactId >h2</ artifactId > < scope >runtime</ scope > </ dependency > < dependency > < groupId >org.springframework.boot</ groupId > < artifactId >spring-boot-starter-test</ artifactId > < scope >test</ scope > </ dependency > </ dependencies > < build > < plugins > < plugin > < groupId >org.springframework.boot</ groupId > < artifactId >spring-boot-maven-plugin</ artifactId > </ plugin > </ plugins > </ build > </ project > |
- spring-boot-starter-data-jpa (required) : It includes spring data, hibernate, HikariCP, JPA API, JPA Implementation (default is hibernate), JDBC and other required libraries.
- h2 : Though we can add any database easily using datasource properties in
application.properties
file, we are using h2 database in reduce unnecessary complexity.
2. Create JPA entity classes
After we have included required jars in classpath, create few entity classes as per project needs. We are here creating one such entity EmployeeEntity for example purpose.
Remember to include only JPA API annotations (javax.persistence.*
) to decouple hibernate from application code.
import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.Table; @Entity @Table (name= "TBL_EMPLOYEES" ) public class EmployeeEntity { @Id @GeneratedValue private Long id; @Column (name= "first_name" ) private String firstName; @Column (name= "last_name" ) private String lastName; @Column (name= "email" , nullable= false , length= 200 ) private String email; //Setters and getters left out for brevity. @Override public String toString() { return "EmployeeEntity [id=" + id + ", firstName=" + firstName + ", lastName=" + lastName + ", email=" + email + "]" ; } } |
- We do not need to do anything to make this class scannable. Spring boot will look for all @Entity annotated classes and configure them by default as JPA entities.
- By default the name of the table is the name of entity class e.g. in above case it shall be
EmployeeEntity
. We can customize the table name using @Table annotation and it’sname
attribute. - The
id
property is annotated with@Id
so that JPA will recognize it as the object’s ID. Also,@GeneratedValue
annotation enable its value generated automatically. - To customize the name of columns,
null
value allowed or size of column etc. use@Column
annotation. - I will suggest to override
toString()
method to print employee’s basic details in logs.
3. Create JPA Repository
Extend JpaRepository
interface to allows to create repository implementations automatically, at runtime, for any given entity class. The types of entity class and it’s ID field are specified in the generic parameters on JpaRepository
.
import org.springframework.data.jpa.repository.JpaRepository; import org.springframework.stereotype.Repository; import com.howtodoinjava.demo.entity.EmployeeEntity; @Repository public interface EmployeeRepository extends JpaRepository<EmployeeEntity, Long> { } |
By this simple extension, EmployeeRepository
inherits several methods for working with Employee
persistence, including methods for saving, deleting, and finding Employee
entities.
Along with default provided methods, we can add our own custom methods and queries to this interface.
4. Properties Configuration
4.1. Data source
Provide the datasource connection properties in application.properties
file which will help in connecting the database to JPA code.
In given config, we are configuring h2 database.
spring.datasource.url=jdbc:h2:file:~/test spring.datasource.driverClassName=org.h2.Driver spring.datasource.username=sa spring.datasource.password= spring.jpa.database-platform=org.hibernate.dialect.H2Dialect # Enabling H2 Console spring.h2.console.enabled= true # Custom H2 Console URL spring.h2.console.path=/h2-console |
4.2. Hibernate print SQL and Logging
A good way to see how the components are working – is to enable extensive logging. Do it when it’s too easy using only few properties entries.
#Turn Statistics on and log SQL stmts spring.jpa.show-sql= true spring.jpa.properties.hibernate.format_sql= true #If want to see very extensive logging spring.jpa.properties.hibernate.generate_statistics= true logging.level.org.hibernate.type=trace logging.level.org.hibernate.stat=debug |
4.3. Database Initialization
In a JPA-based applications, we can either choose to let Hibernate create the schema using entity classes or use schema.sql
, but we cannot do both.
Make sure to disable spring.jpa.hibernate.ddl-auto if using schema.sql
.
#Schema will be created using schema.sql and data.sql files spring.jpa.hibernate.ddl-auto=none |
DROP TABLE IF EXISTS TBL_EMPLOYEES; CREATE TABLE TBL_EMPLOYEES ( id INT AUTO_INCREMENT PRIMARY KEY, first_name VARCHAR( 250 ) NOT NULL, last_name VARCHAR( 250 ) NOT NULL, email VARCHAR( 250 ) DEFAULT NULL ); |
INSERT INTO TBL_EMPLOYEES (first_name, last_name, email) VALUES ( 'Lokesh' , 'Gupta' , 'abc@gmail.com' ), ( 'Deja' , 'Vu' , 'xyz@email.com' ), ( 'Caption' , 'America' , 'cap@marvel.com' ); |
5. Spring boot hibernate demo
To test hibernate configuration with Spring boot, we need to autowire the EmployeeRepository
dependency in a class and use it’s method to save or fetch employee entities.
Let’s do this testing in @SpringBootApplication
annotated class and using CommandLineRunner
interface. The run()
method from CommandLineRunner
is executed immediately after the application startup.
package com.howtodoinjava.demo; import java.util.Optional; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.boot.CommandLineRunner; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import com.howtodoinjava.demo.entity.EmployeeEntity; import com.howtodoinjava.demo.repository.EmployeeRepository; @SpringBootApplication public class SpringBoot2DemoApplication implements CommandLineRunner { private Logger logger = LoggerFactory.getLogger( this .getClass()); @Autowired EmployeeRepository repository; public static void main(String[] args) { SpringApplication.run(SpringBoot2DemoApplication. class , args); } @Override public void run(String... args) throws Exception { Optional<EmployeeEntity> emp = repository.findById(2L); logger.info( "Employee id 2 -> {}" , emp.get()); } } |
Run the application and observe the output. Please note that to print limited information in logs, I am using property logging.pattern.console=%m%n in application
Tomcat initialized with port(s): 8080 (http) Starting service [Tomcat] Starting Servlet engine: [Apache Tomcat/ 9.0 . 19 ] Initializing Spring embedded WebApplicationContext Root WebApplicationContext: initialization completed in 5748 ms HikariPool- 1 - Starting... HikariPool- 1 - Start completed. HHH000204: Processing PersistenceUnitInfo [ name: default ...] HHH000412: Hibernate Core { 5.3 . 10 .Final} HHH000206: hibernate.properties not found HCANN000001: Hibernate Commons Annotations { 5.0 . 4 .Final} HHH000400: Using dialect: org.hibernate.dialect.H2Dialect Initialized JPA EntityManagerFactory for persistence unit 'default' Initializing ExecutorService 'applicationTaskExecutor' spring.jpa.open-in-view is enabled by default . Therefore, database queries may be performed during view rendering. Explicitly configure spring.jpa.open-in-view to disable this warning Tomcat started on port(s): 8080 (http) with context path '' Started SpringBoot2DemoApplication in 17.638 seconds (JVM running for 19.1 ) Hibernate: select employeeen0_.id as id1_0_0_, employeeen0_.email as email2_0_0_, employeeen0_.first_name as first_na3_0_0_, employeeen0_.last_name as last_nam4_0_0_ from tbl_employees employeeen0_ where employeeen0_.id=? Employee id 2 -> EmployeeEntity [id= 2 , firstName=Deja, lastName=Vu, email=xyz @email .com] |
Clearly, hibernate has been configured and we are able to interact with database using JPA repository interface.
Drop me your questions in comments sections related to configuring hibernate with spring boot.
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