jpa – icod.de Webentwicklung

What are fixtures? Fixed data that is always present in the database. You can think of it as the initial dataset.

application.properties

spring.jpa.hibernate.ddl-auto=create
spring.jpa.generate-ddl=true
spring.jpa.open-in-view=false
spring.sql.init.mode=always
spring.sql.init.data-locations=classpath:db/data.sql
spring.jpa.defer-datasource-initialization=true

spring.jpa.hibernate.ddl-auto=create

spring.jpa.generate-ddl=true

spring.jpa.open-in-view=false

spring.sql.init.mode=always

spring.sql.init.data-locations=classpath:db/data.sql

spring.jpa.defer-datasource-initialization=true

The documentation speaks of “the root classpath”, not knowing Java well I had no idea what that means and an answer on Stackoverflow was of course wrong.
It’s not the “src” dir, but the “resources” dir.

So with the above configuration we set spring.sql.init.data-locations=classpath:db/data.sql
which means we create a directory named “db” under src/main/resources.
Also we create a file named “data.sql”.

If you have spring.jpa.hibernate.ddl-auto=create but not spring.jpa.defer-datasource-initialization=true, data.sql will be executed before the schema is created by JPA and then the tables will be destroyed and created.

data.sql obviously contains sql statements like INSERT INTO profiles (name) VALUES('Darko').
data.sql is only for data, don’t use it for schema.
The location setting for schema is spring.sql.init.schema-locations= e.g. spring.sql.init.schema-locations=classpath:db/schema.sql.
Since you’re using schema.sql you don’t need to defer data initialization.

Details at the Spring Boot JPA reference documentation

I read lots of outdated info on this matter.

Using PostgreSQL v13+ there is a function called gen_random_uuid().
See the manual page of Postgres UUID.

Here’s an example entity called Page

package de.icod.blog.model;

import javax.persistence.*;
import java.util.UUID;

@Entity
@Table(name = "page")
public class Page {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id", nullable = false, columnDefinition = "UUID default gen_random_uuid()")
    private UUID id;

    public UUID getId() {
        return id;
    }

    public void setId(UUID id) {
        this.id = id;
    }
}

package de.icod.blog.model;

import javax.persistence.*;

import java.util.UUID;

@Entity

@Table(name = "page")

public class Page {

@Id

@GeneratedValue(strategy = GenerationType.AUTO)

@Column(name = "id", nullable = false, columnDefinition = "UUID default gen_random_uuid()")

private UUID id;

public UUID getId() {

return id;

}

public void setId(UUID id) {

this.id = id;

}

As you see you can append the columnDefinition to the @Column annotation. “UUID default gen_random_uuid()”
This translates to following SQL

create table page
(
    id uuid default gen_random_uuid() not null
        constraint "primary"
            primary key
);

create table page

(

id uuid default gen_random_uuid() not null

constraint "primary"

primary key

);

And you don’t have to worry about having an empty ID when inserting records.

Tag: jpa

Spring Data JPA fixtures

Spring Data JPA Postgres UUID @Id