Overview of This Lesson

Refresh this page because I am probably still making changes to it.

In this lesson you'll learn how to use a persistent storage mechanism such as MySQL Server to store data instead of (or with) an in-memory database. You'll also learn to use profiles to easily switch from one run configuration to another, for easy testing and debugging.


Before doing this tutorial, make sure you've completed all of the JDBC lessons and that you've also Installed and Configured MySQL Server

Persistent Storage

In previous lessons you learned how to code JDBC in your Spring Boot applications by using H2, an in-memory database. There will be times when you will want to use persistent storage: storage that persists between application restarts.

For example, you might want to store the players on different sports teams so you can go back any time and view the players you've saved. In an inventory application, you would definitely want to store the inventory records persistently so that you always had an updated set of information about what products are in stock. If you ran an online store, you'd want some permanent storage for all of the customer information and all of their orders and payments.

For persistent storage in a Spring Boot application, we generally go with MySQL server: it's free and it's used a lot in industry already.

If you haven't already, make sure you install MySQL Server and Workbench before you proceed with the rest of this lesson.

Make sure the MySQL service is running: if you selected the configuration option to start MySQL Server at system startup, then it's likely already running. If you didn't select this option, just go to Services (in Windows, search for "Services" and run the Services application) and find MySQL80 and start the service.

Run Workbench and connect to your database server. Add a new database called "logindb" where "login" is your Sheridan login name (so if your login is fred, then your db name would be freddb):

Alternatively, if you prefer, you can just use a new SQL statement:

USE logindb;

Using MySQL Server in your Spring applications is not much different from using H2: you just need to make sure you add the MySQL Driver dependency to your project and then add a few properties in the application.properties file.

Start up a new project and add the following dependencies:

Next, open the application properties file and add the following:


These statements indicate that you're going to use MySQL server as the database, that you're going to connect to the database using the connection string "jdbc:mysql://localhost:3306/", and that you want to USE the database called "logindb" (except yours has your own Sheridan login instead of "login").

Additionally, when you set up MySQL server, you added a root account and an Admin account. The root account is powerful: the root account can do ANYTHING with the database and the database server. The Admin account is less powerful, but probably still has too much power than we want for the average user.

When an unauthenticated user visits your application, you don't want that user to have any database access at all. Once a user is authenticated, you only want that user to have whatever permissions they need to do what they are able to do. For example, a customer should only be able to view their own customer account and update some of their own data, but they should not have permissions to add or delete other records in the customers table, nor should they be allowed to perform any kind of data manipulation operations on the products/inventory table.

So when you're setting up your project to use MySQL, you'll want to set it up to use only those users with the most limited access to your database. You should NEVER use the root account as the default account for your application: not only does this give a hacker complete power over your entire dataase server, but it makes it easy for another member of your team to do some serious accidental damage.

You can easily create additional users using the UI in MySQL Workbench:

Alternatively, you can just open a new SQL window and type statements such as:

CREATE USER IF NOT EXISTS 'dbUser'@'localhost' IDENTIFIED BY 'dbPassword';
GRANT SELECT, INSERT, UPDATE, DELETE ON dbName.* TO 'dbUser'@'localhost';

Where "dbUser" is the name of the user account, "dbPassword" is the password assigned to this account, and "dbName" is the name of the database where this user has specific privileges granted to them.

In the example above, the user "dbUser" can do CRUD operations, but nothing else.

For our example today, make sure your user has the ability to do basic CRUD operations on the logindb database.

Once you've created the user(s) you will need, choose the default for visitors to your application and add that information to your application.properties file:


Make sure you replace "dbUser" and "dbPassword" with the actual username and password for your user. For these exercises, make sure this user has access to CRUD operations, but nothing else.

Now copy over the Player and Team beans from the database project you did in the CRUD Operations lessons (or feel free to use any database project where you have at least one read and one insert operation).

Copy over the database classes and any HTML form input and/or tabular output that allows a user to insert a new player and list all the players (I think in the last version of the Player/Team project, we did the input and the output on a single HTML page).

In that same project, you had a schema.sql and data.sql file that created the teams and players table and populated the teams table with teams. Copy the code inside those 2 files and paste it into an SQL window in Workbench. Add the command USE logindb; (but with your own Sheridan login instead of "login") above all of the other code. Then execute the SQL code by clicking on the lightning bold button on top of the query window.

the sql code that uses the logindb database, creates players and teams tables, and populates teams, also adds foreign key players.team to teams.id
Execute the SQL that creates the database schemas.

That's it.

No really, that's it.

Run your program, add a new player, etc: it works just like it did back in week 5. If you don't believe me, go back to Workbench and type "SELECT * FROM players;" in a new SQL query window. See?

Why was this so easy??!!

Because you have been using SOLID principles!! We created all of our database configuration and database access code in separate classes, and we wrote it all in such a way that we could easily switch database technologies with very little effort!!

If you wanted to switch back to H2, that would also be super easy, and in fact, we'll do that next, just so you can see how simple it really is.


When we develop applications that use a database, we don't want to do the testing on the actual database server: testing can be resource-intensive, and we don't want to slow down the same database server that the actual users are currently using! They will notice the slowness and get annoyed, and might even stop using the application in favour of a faster one.

For this reason, it's common to use H2 or other in-memory database for testing, and then switch to the actual database server (i.e. MySQL) for production. Because you've developed your application using good design principles, including SOLID, this is really easy to do!

Spring allows you to easily set up different profiles. A profile is just a collection of settings and configuration information. For example, you can use one profile for developing, testing, and debugging, and a completely different profile for deployment and production.

In our example application, let's set up a "development" profile that we'll use whenever we want to come back and continue development on our application, perform tests, add new features, debug, etc. Typically you would actually use this as the default profile and then set up a separate profile for production, but we're doing it backwards today!

Create a new profile by simply adding a new .properties file to the /resources directory. The name of the properties file should be application-profilename.properties, where the value "profilename" is the name of this profile. Make sure you use a dash to separate the word "application" from the profile name. Let's add the development profile:

Now just add the normal properties you would use when you want to use H2 as the database:


Notice the extra property spring.jpa.database=h2. This extra property says that we're using H2 for this profile (in the past, it was detected automatically). It's a good idea to have this extra line in here when you're working with different profiles that have different database vendors.

Also, you might find that when you add spring.jpa.database=h2, you may not actually need to also specify driverClassName because it's detected automatically when you set the database vendor to H2.

Since you're using H2 for development, make sure you copy your schema.sql and data.sql files over to this project. H2 needs those files to create the database schema and load the teams table.

Now create the production profile: add another properties file but call this one application-prod.properties.

In the application-prod.properties file, add the properties to use your MySQL database:


(Remember that logindb uses your own login name and dbUser/dbPassword refer to the user you added that has permission to perform basic CRUD operations)

How do we make sure the project runs with a specific profile? You create a Run Configuration for it:

select your Profile in the run configuration
Edit the Run Configuration and select the new profile

We might as well try it out, though. so click the Run button if you're still in the dialog. If you're not in the dialog, you can just run the project normally now, as long as you changed the profile in the run configuration.

Your program runs! How do you know for sure that it's using H2? Run the H2 console.

If you ever want to switch profiles, go back to the application properties file and change the spring.profile.active value (or swap the commented lines, if appropriate). Then set the profile for the run configuration.

Now you know how to easily switch between different environments by using profiles, and also how to switch between different database vendors! It's so easy because you started out using good design principles. :)


Go to one of your previous database projects and add a production profile (e.g. "-prod") that allows you to use MySQL Server in a production environment. Test out your project with the new profile. Make sure MySQL server is running!