SpringBoot and Database

What you will build
You will create a database, build a Spring application, and connect it to the newly created database.

What you will need
The database is provided on the devtools website, and we are going to use Spring Tool suite but you can use another IDE such as IntelliJ.

A note on MySQL/MariaDB
We will be using MariaDB, which is an almost identical fork of MySQL. The interested can find details about the relationship between the two on Wikipedia, but the short version is that they are mostly interchangeable. We will be using the names interchangably, except in cases where there is a difference that matters, in which case it will be clearly stated that the difference is important. Similarly, most MySQL resources on the web will apply equally to MariaDB and vice versa.

A nice thing that we can do with spring boot JPA and MySQL are that we can start with an empty database (by that I mean there are no tables inside of it) and then we can use some annotations to transfer our data transfer object (DTO) and we can have spring boot automatically map the Data transfer object to the database.

Create a database

Create mariaDB database available on the university server at https://devtools.dsv.su.se
After you create your database you will get the following information as shown in the picture below to connect with your database:
Use a database management application to connect to your database. Some suggested options for database management are DBeaver (cross-platform, must use the MariaDB database driver for connections) or Sequel Pro (for mac). Create a new connection in your management application and fill in the details of the database you created.
After that click on Test connection, and when it connects successfully, Save changes. This step is to make sure that you can connect to your database successfully.

Configure your application to access your database

After you have created the database, then you need to setup a little bit of configuration information in your application properties file in spring boot application. All you need to do is to say what is that URL to your database, the username, the password, and the driver.

We are going to follow the example on Spring guides: https://spring.io/guides/gs/accessing-data-mysql/#scratch

Now you need to add the dependencies for JPA and MySql drivers to your pom file, and make sure that the web dependency is added:

          <!-- Spring web -->
          <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
          </dependency>

          <!-- Spring data JPA -->
          <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
          </dependency>

          <!-- MySQL driver -->
          <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
          </dependency>

          <dependency>
            <groupId>javax.xml.bind</groupId>
            <artifactId>jaxb-api</artifactId>
            <version>2.3.0</version>
          </dependency>

Create the @Entity Model (DTO)
Hibernate automatically translates the entity into a table. You need to have DTO (Data transfer object), where you use some simple annotations on that DTO.
- @Entity says that this is a Data transfer object or java bean, and I want this DTO to persist to a database
- @id and @generatedvalue say that this is the primary key and I want it to be autogenerated
Create a repository that holds user records, by extending an interface called crudrepository.
Create a controller using the @controller annotation, which will handle HTTP requests to your application.
This is the application architecture

Test the application

Run your application. You should now be able to send a request to add an entry to the database or retrieve all records from the database.
You can use send a request using any API for testing such as postman: https://www.postman.com/downloads/
Add a record to database by sending a post request to the server, in this example it is localhost:
```
localhost:8080/demo/add?name=john&email=john@su.se
```
You can check that the user has been added if you go to your database manager and look at the table contents there.
You can get all the records from database by sending a get request to the server:
```
localhost:8080/demo/all
```