Configuration precedence order in Spring Boot - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to specify the highest precedence configuration source in Spring Boot.

Spring Boot

spring.config.location=[1]

Drag options to blanks, or click blank then click option'

Aenvironment variables

Bapplication.yml

Cclasspath:/application.properties

Dcommand-line arguments

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing environment variables instead of command-line arguments

Confusing classpath properties with runtime overrides

Command-line arguments have the highest precedence in Spring Boot configuration order.

2fill in blank

medium

Complete the code to indicate the default configuration file Spring Boot loads from the classpath.

Spring Boot

spring.config.name=[1]

Drag options to blanks, or click blank then click option'

Aapplication.properties

Bapplication

Capplication.yml

Dconfig

Attempts:

3 left

💡 Hint

Common Mistakes

Including the file extension in the config name

Using 'config' instead of 'application'

Spring Boot loads configuration from a file named 'application' with supported extensions like .properties or .yml by default.

3fill in blank

hard

Fix the error in the code to correctly specify a profile-specific configuration file in Spring Boot.

Spring Boot

spring.config.location=classpath:/application-[1].properties

Drag options to blanks, or click blank then click option'

Adev

Bdefault

Cactive

Dprofile

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'profile' or 'active' literally instead of the profile name

Using 'default' which is not a profile

The profile name 'dev' is commonly used to load development-specific configuration files like application-dev.properties.

4fill in blank

hard

Fill both blanks to complete the code that sets the order of configuration precedence: first environment variables, then {{BLANK_1}}.

Spring Boot

spring.config.import=optional:configtree:./config/,{{BLANK_2}}

Drag options to blanks, or click blank then click option'

Aapplication.properties

Bcommand-line arguments

Cclasspath:/application.properties

Denvironment variables

Attempts:

3 left

💡 Hint

Common Mistakes

Reversing the order of command-line arguments and classpath properties

Confusing environment variables with configtree

After environment variables, Spring Boot loads from classpath application.properties, then command-line arguments override all.

5fill in blank

hard

Fill all three blanks to complete the code that defines a configuration property with a default value, overridden by {{BLANK_1}}, then {{BLANK_2}}, and finally {{BLANK_3}}.

Spring Boot

spring.config.override=[1],[2],[3]

Drag options to blanks, or click blank then click option'

Aapplication.properties

Benvironment variables

Ccommand-line arguments

Dprofile-specific properties

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up the order of environment variables and command-line arguments

Including profile-specific properties in the wrong position

The order is default application.properties, then environment variables, and finally command-line arguments which have the highest precedence.

Practice

1. In Spring Boot, which configuration source has the highest priority and overrides all others?

easy

A. Environment variables

B. Command line arguments

C. application.properties file

D. Default properties in code

Solution

1. Step 1: Understand configuration sources in Spring Boot

   Spring Boot loads configuration from multiple sources like properties files, environment variables, and command line arguments.

2. Step 2: Identify the highest priority source

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

3. Final Answer:

   Command line arguments -> Option B

4. Quick Check:

   Highest priority = Command line arguments [OK]

Hint: Remember: command line args always override others [OK]

Common Mistakes:

• Thinking application.properties has highest priority
• Confusing environment variables with command line args
• Assuming default properties override others

2. Which of the following is the correct way to specify a property in Spring Boot's application.properties file?

easy

A. server.port=8080

B. server-port:8080

C. server_port=8080

D. serverPort=8080

Solution

1. Step 1: Recall Spring Boot property syntax

   Spring Boot uses dot notation in application.properties files, like server.port=8080.

2. Step 2: Check each option's syntax

   server.port=8080 uses correct dot notation. Options B, C, and D use invalid separators or camelCase which are not valid in properties files.

3. Final Answer:

   server.port=8080 -> Option A

4. Quick Check:

   Properties use dot notation = server.port=8080 [OK]

Hint: Use dot notation for properties in application.properties [OK]

Common Mistakes:

• Using underscores instead of dots
• Using colon instead of equals sign
• Using camelCase instead of dot notation

3. Given the following Spring Boot configuration sources:
application.properties sets server.port=8080
Environment variable SERVER_PORT=9090
Command line argument --server.port=7070
What port will the application run on?

medium

A. 7070

B. 9090

C. Default port 8081

D. 8080

Solution

1. Step 1: List configuration sources and their values

   application.properties: 8080, environment variable: 9090, command line argument: 7070.

2. Step 2: Apply Spring Boot precedence order

   Command line arguments override environment variables and properties files, so port is 7070.

3. Final Answer:

   7070 -> Option A

4. Quick Check:

   Command line args override others = 7070 [OK]

Hint: Command line args always win over env and properties [OK]

Common Mistakes:

• Choosing environment variable value instead of command line
• Assuming properties file overrides environment variables
• Forgetting default port fallback

4. You set server.port=8080 in application.properties and also pass --server.port=9090 as a command line argument, but the app still runs on port 8080. What is the most likely cause?

medium

A. application.properties has higher priority

B. Spring Boot ignores command line arguments by default

C. Environment variable overrides command line

D. Command line argument syntax is incorrect

Solution

1. Step 1: Understand expected behavior

   Command line arguments should override properties file settings.

2. Step 2: Identify why command line arg might be ignored

   If the syntax is wrong (e.g., missing dashes or wrong format), Spring Boot won't apply it.

3. Final Answer:

   Command line argument syntax is incorrect -> Option D

4. Quick Check:

   Incorrect syntax means command line ignored [OK]

Hint: Check command line argument format carefully [OK]

Common Mistakes:

• Assuming properties file always overrides command line
• Thinking environment variables override command line
• Believing Spring Boot ignores command line args by default

5. You want to set a default property app.mode=dev in your Spring Boot app but allow it to be overridden by environment variables or command line arguments. Which order of precedence correctly applies?

hard

A. Environment variables < Command line arguments < application.properties < Default properties

B. Command line arguments < Environment variables < application.properties < Default properties

C. Default properties < application.properties < Environment variables < Command line arguments

D. application.properties < Default properties < Command line arguments < Environment variables

Solution

1. Step 1: Understand default property placement

   Default properties are lowest priority and can be overridden by all other sources.

2. Step 2: Recall Spring Boot precedence order

   Order is: Default properties < application.properties < Environment variables < Command line arguments.

3. Final Answer:

   Default properties < application.properties < Environment variables < Command line arguments -> Option C

4. Quick Check:

   Lowest to highest priority = Default properties < application.properties < Environment variables < Command line arguments [OK]

Hint: Remember: default < properties < env vars < command line [OK]

Common Mistakes:

• Mixing order of environment variables and properties file
• Placing default properties above application.properties
• Reversing command line argument priority