Spring Boot Externalized Configuration and Profiles Questions and Answers

Question 1

A Spring Boot application defines the property `server.port=8080` in its `application.properties` file.
An OS environment variable is set as `SERVER_PORT=7070`.
The application is then launched with the command: `java -jar app.jar --server.port=9090`.
On which port will the application start?

Accepted Answer

9090

Answer

8080

Answer

7070

Answer

The application will fail to start due to a configuration conflict.

Question 2

A developer needs to create a configuration bean that is only active when the `production` profile is NOT active. Which annotation should be used on the bean's definition to achieve this?

Accepted Answer

@Profile("!production")

Answer

@Profile("not production")

Answer

@ConditionalOnMissingProfile("production")

Answer

@Profile("default")

Question 3

A developer wants to bind a group of related properties under the prefix `app.credentials` to a type-safe POJO class. Which annotation is the most idiomatic and robust way to achieve this in Spring Boot?

Accepted Answer

Using `@ConfigurationProperties(prefix = "app.credentials")` on the POJO.

Answer

Using individual `@Value` annotations for each field in the POJO.

Answer

Manually binding properties from the `Environment` object.

Answer

Using `@PropertySource` to load the properties into the class.

Question 4

An application has an `application-dev.properties` file with `logging.level.root=DEBUG` and an `application-prod.properties` file with `logging.level.root=WARN`. If the application is launched with `spring.profiles.active=dev,prod`, what will be the effective root logging level?

Accepted Answer

WARN

Answer

DEBUG

Answer

INFO (the default)

Answer

The application will fail due to conflicting properties.

Question 5

Which of the following `application.yml` snippets correctly configures a list of strings for the property `myapp.api-keys`?

Accepted Answer

myapp:
  api-keys:
    - key1
    - key2
    - key3

Answer

myapp.api-keys: [key1, key2, key3]

Answer

myapp:
  api-keys: key1, key2, key3

Answer

myapp.api-keys[0]=key1
myapp.api-keys[1]=key2
myapp.api-keys[2]=key3

Question 6

A developer injects a property into an integer field using `@Value("${app.connection.pool-size:30}")`. If the `app.connection.pool-size` property is not defined in any configuration source, what will be the outcome?

Accepted Answer

The `pool-size` field will be initialized to `30`.

Answer

The application will fail to start because the property cannot be resolved.

Answer

The `pool-size` field will be `null`.

Answer

The `pool-size` field will be initialized to `0`.