Why is spring boot connecting to database successfully

[viscid comet]

I'm following a youtube spring boot tutorial and I have a few questions about why/how it is working.

I'm using spring boot postgres driver & docker-compose support.

Images + questions to follow...

[severe smelt]

<@&1004656351647117403> please have a look, thanks.

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I'm following a youtube spring boot tutorial and I have a few questions about why/how it is working. I'm using spring boot `postgres driver` & `docker-compose support`. Images + questions to follow...

spring-boot-starter-data-jpadependencies in my project. When I configure theapplication.properties` file with the database URL, username, and password, Spring Boot automatically uses these configurations to establish a connection to the database.

Spring Boot simplifies the process of connecting to a database by providing auto-configuration features. It scans the classpath and automatically configures beans based on the dependencies present in the project. In this case, when it detects the postgres driver and spring-boot-starter-data-jpa dependencies, it sets up a data source bean for connecting to a PostgreSQL database.

Additionally, Spring Boot utilizes Hibernate as its default JPA implementation. When you create a repository interface extending JpaRepository or CrudRepository, Spring Boot generates the necessary SQL queries at runtime based on method names. This eliminates the need to write boilerplate code for basic CRUD operations.

Overall, Spring Boot's convention over configuration approach and built-in features make it easy to connect to databases and perform database operations without much manual configuration or coding effort.

If you have any specific questions or issues with your Spring Boot project's database connection, feel free to ask for help here!

- AI generated response

[viscid comet]

I have these properties in application.properties

and this docker-compose.yml

My questions:

1. What's the purpose of spring.datasource.url?
   I can connect via JDBC url in my GUI client jdbc:postgresql://localhost:5432/mydatabase
   but isn't that URL autogenerated with dbName + user + password?

Why is it configurable in application.properties ?
When I try to connect with the spring.datasource.url in my client, it doesn't work. So it doesn't seem like it's configuring anything.

2. The username and password properties are blank; the DB username and password are provided in the docker-compose.
Is the spring boot docker-compose support dependency configuring Spring Boot to read the credentials from docker-compose.yml to make the DB connection?

[viscid comet]

For question 2, I think it was working with blank username & password because my docker-compose had the default values. After I changed them, it stopped working and I had to define them in application.properties

But still I don't know what datasource.url does.
If I put a wrong jdbc url as the value, my app still connects to the DB.