Initialize a Database Using SQL Scripts with Spring Boot

1. Story

  • There are many cases in which we need to initialize an SQL database at application startup.
  • Either creating schema based on DDL scripts or feeding initializing data into database by DML scripts may be required in application startup.
  • Spring Boot provides simple features for developers to run both DDL and DML scripts automatically.
  • In this post we use this feature practically.

2. Create Project

You can find the complete project at Github.

Create a new project by using online Spring initializer either at or on Intellij _Idea > New Project > Spring Initializr.

And in dependencies window select 3 dependencies that we named them in "dependencies section" of this post.

3. Dependencies

The only needed dependency that do the job for running SQL scripts automatically is spring-boot-starter-data-jdbc. But we also want to use h2database as a simple embeded database. And at last we use spring-boot-starter-web to make our project a simple running project, so our dependencies in pom.xml file looks like this:

4. Configure H2 Database

Because of its simplicity we choose embedded h2 as our SQL databse. So no need to have a SQL database like MySQL or Oracle to be installed on your environment.

H2 is a lightweight SQL database written by Java which can also be embedded in a Java application(in memory).

And now as you can guess is the time for telling Spring_data_jdbc how to connect to our database instance of h2. We tell these things as some configuration statements. So let's open "" file in "resources" folder and fill it like this one:

Please note that we want to have a GUI from h2 so we added "spring.h2.console.enabled=true" in the properties file. And by this setting by running the application, we also will have an h2 console on our web-browser which we talk about it in following sections of this post.

Other properties are about addressing our desired h2 database. These settings seems to be much clear and self descriptive.

5. DDL Scripts

In SQL, DDL stands for Data Definition Language. DDL statements create, modify, and remove database objects such as tables and indexes.

We add a file named schema.sql to the resource folder to be loaded to classpath. This file should contains all the DDL scripts for our desired database schema.

6. DML Scripts

In SQL, DML stands for Data Manipulation Language. DML statementa used for adding (inserting), deleting, and modifying (updating) data in a database.

In this step we create a file named "data.sql" in "resource" folder to be added into the classpath and fill it with our desired DML statements:

There are two insert command in our data.sql file and of course you can add any other commands for INSERT, UPDATE, and DELETE data.

7. See Results in Console

Hey congrats, that's all, now you can run your application and if there is no bugs you would get a message like "Started DatabaseInitializationApplication in 1.828 seconds (JVM running for 2.548)" in your console/terminal.

So good. Let's open a browse and go to http://localhost:8080/h2-console. Login with the credentials that you declared in file.

And at last you can find your automatically generated table(s) with its inserted data in the h2 console just like below image.

8. Multi Datasources

If you need more than one datasource in your application, then you must determine one of them as the primary one, so Spring-data-jdbc can do things on this primary datasource.

If you do not determine the primary datasource then while starting the application h2console and also Spring-data-jdbc could not find a primary datasource and return error message. So we add second datasource properties in the file and also we define two beans for primary and second datasource and determine one of them with @Primary.

9. Further Reading

Spring Boot can also supports Higher-level Migration Tools, like Flyway or Liquibase for doing database migrations at startup. This topic is out of the context of this post and you can read more about that in Spring Documents.

Thanks for Reading. Good lock.


Simple Java + Docker

1. Introduction

As a Java developer I want to build a lean Docker image for my java app. A Docker feature named "multi-stage builds" make this process so easy and straight forward.

2. Sample Project

As a simple sample project we have a Spring-Boot hello world project which responses on http://localhost:8080 You can provide your desired project or clone/download the github repository from here:

3. Dockerfile

In the root of the project there would be a file named Dockerfile containing below listing:

4. How to run

  1. Docker must be installed on your system
  2. In terminal go to root of the project and run below command for building docker image:
  3. * Please notice that there is a dot(.) at the end of above command.
  4. In terminal run below commands for running the container:
  5. Check your application in browser: Go to browser and browse into http:\\localhost:8080
  6. Check your docker container: Go to terminal and run below command:

5. Next

Below, a couple of points are mentioned which are not described here to keep this article simple.

  • Use -v option of docker for mounting your local maven repository and prevent downloading maven dependencies in build repetitive phase.
  • Use Maven plugins for building images instead of direct docker CLI commands.
  • Push docker image into a docker hub to make it accessible from hosts outer of your local.