Configuration precedence order in Spring Boot - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the configuration precedence order in Spring Boot?

Spring Boot loads configuration properties in a specific order where properties defined later override earlier ones. The order is: 1) Command line arguments, 2) Java System properties, 3) OS environment variables, 4) Application properties inside jar (application.properties or application.yml), 5) Default properties.

beginner

Which configuration source has the highest priority in Spring Boot?

Command line arguments have the highest priority and override all other configuration sources.

intermediate

How do environment variables rank in Spring Boot's configuration precedence?

Environment variables have lower priority than command line arguments and Java system properties but higher than application properties inside the jar.

intermediate

What happens if the same property is defined in both application.properties and as a system property?

The system property value overrides the value defined in application.properties because system properties have higher precedence.

beginner

Why is understanding configuration precedence important in Spring Boot?

It helps you know which configuration value will be used when the same property is defined in multiple places, avoiding confusion and bugs.

Which configuration source has the lowest priority in Spring Boot?

A Java System properties

B Application properties inside jar

C Command line arguments

D Environment variables

Application properties inside the jar have lower priority than command line arguments, system properties, and environment variables.

If a property is set both as an environment variable and a command line argument, which one is used?

A Command line argument

B Depends on OS

C Environment variable

D Both are merged

Command line arguments have higher precedence than environment variables.

Where does Spring Boot look for application.properties by default?

A Only in external config folder

B Only in command line arguments

C Only in environment variables

D Inside the jar file

Spring Boot loads application.properties or application.yml inside the jar by default.

Which of these is NOT a valid configuration source in Spring Boot?

A Command line arguments

B Java System properties

C Database configuration table

D Environment variables

Spring Boot does not load configuration from a database table by default.

If a property is missing in all sources, what does Spring Boot do?

A Uses a default value if defined

B Throws an error

C Asks user input

D Skips the property silently

Spring Boot uses default values if defined, otherwise the property remains unset.

Explain the order in which Spring Boot loads configuration properties and why this order matters.

Think about where you can set properties and which one wins if duplicates exist.

Describe a scenario where understanding configuration precedence can help avoid bugs in a Spring Boot application.

Consider when a developer sets a property in environment and also in command line.