spring 基于环境变量的引导自动配置

Question

In my understanding in a spring-boot application when having spring-boot-starter-data-jpa on your classpath and also mysql-connector spring-boot will still try to use in memory h2 (as per default), if no db related properties are defined.

But if you have properties like the following:

spring.jpa.hibernate.ddl-auto=update
spring.datasource.url=jdbc:mysql://${MYSQL_HOST:localhost}:3306/db_example
spring.datasource.username=springuser
spring.datasource.password=ThePassword

It will use mysql database.

My question is: what happens if you have those properties only declared as environmental variables? Is this behaviour still valid?

thanks!

Answer 1

I tried using the following dependencies together: "web", "mysql", "jpa". A simple run without any configuration shows the following error:

***************************
APPLICATION FAILED TO START
***************************

Description:

Failed to configure a DataSource: 'url' attribute is not specified and no embedded datasource could be configured.

Reason: Failed to determine a suitable driver class


Action:

Consider the following:
    If you want an embedded database (H2, HSQL or Derby), please put it on the classpath.
    If you have database settings to be loaded from a particular profile you may need to activate it (no profiles are currently active).

And if you use the environment route instead of "application.properties" as long as you set them correctly it should act the same as a fully configured "application.properties" file.