application.yml alternative in Spring Boot - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Alternative to application.yml for configuration in Spring Boot

Which file can be used as a direct alternative to application.yml for defining configuration properties in Spring Boot?

A settings.json

B config.xml

C application.properties

D config.yaml

💡 Hint

Think about the default property file format supported by Spring Boot besides YAML.

Spring Boot supports application.properties as the standard alternative to application.yml for configuration. Both serve the same purpose but use different formats.

❓ component_behavior

intermediate

Behavior difference between application.yml and application.properties

What is a key difference in how Spring Boot processes application.yml compared to application.properties?

A YAML supports hierarchical data structures natively, properties file uses dot notation for nesting

B YAML files are ignored if properties file exists

C Properties file supports lists natively, YAML does not

D Properties files require explicit type declarations, YAML does not

💡 Hint

Consider how nested configuration is represented in each format.

YAML allows nested structures using indentation, making it easier to represent complex configurations. Properties files use dot notation keys to simulate nesting.

📝 Syntax

advanced

Correct syntax for list in application.properties

How do you define a list of values for a property named app.servers in application.properties?

A app.servers=server1,server2,server3

B app.servers=[server1, server2, server3]

C

app.servers:
  - server1
  - server2
  - server3

D app.servers=server1;server2;server3

💡 Hint

Think about how lists are represented in properties files.

In application.properties, lists are represented as comma-separated values in a single line.

🔧 Debug

advanced

Why does Spring Boot ignore my application.properties file?

You have both application.yml and application.properties in your Spring Boot project. You update application.properties but changes are not reflected at runtime. What is the most likely reason?

A application.properties must be renamed to config.properties to be recognized

B Spring Boot gives priority to application.yml over application.properties by default

C application.properties is only loaded if application.yml is missing

D Spring Boot requires a command line flag to enable properties file loading

💡 Hint

Consider the order in which Spring Boot loads configuration files.

Spring Boot loads application.yml before application.properties, but properties in application.yml override those in application.properties if both exist.

❓ state_output

expert

Resulting property value with multiple config files

Given these files in a Spring Boot project:

application.yml:
server:
port: 8080

application.properties:
server.port=9090

What port will the embedded server run on?

A Application fails to start due to conflicting configs

B 9090

C Default port 8080 is used ignoring both files

D 8080

💡 Hint

Remember the precedence rules of Spring Boot configuration files.

Spring Boot gives higher priority to application.yml over application.properties. So the port 8080 from YAML is used.

Practice

1. Which file format is a common alternative to application.yml in Spring Boot for configuration?

easy

A. config.ini

B. config.xml

C. settings.json

D. application.properties

Solution

1. Step 1: Understand Spring Boot configuration files

   Spring Boot supports multiple configuration file formats, but the two most common are application.yml and application.properties.

2. Step 2: Identify the alternative format

   The application.properties file uses simple key=value pairs and is widely used as an alternative to YAML files.

3. Final Answer:

   application.properties -> Option D

4. Quick Check:

   Alternative to application.yml = application.properties [OK]

Hint: Remember: properties files use key=value lines [OK]

Common Mistakes:

• Confusing XML or JSON as default Spring Boot config
• Thinking config.ini is supported by Spring Boot
• Assuming YAML is the only option

2. Which of the following is the correct syntax for setting a server port in application.properties?

easy

A. server.port=8080

B. server.port => 8080

C. server.port : 8080

D. server.port -> 8080

Solution

1. Step 1: Recall properties file syntax

   In application.properties, each configuration is set as a key=value pair without colons or arrows.

2. Step 2: Identify the correct key-value format

   The correct syntax uses an equals sign: server.port=8080.

3. Final Answer:

   server.port=8080 -> Option A

4. Quick Check:

   Properties syntax uses = not : or arrows [OK]

Hint: Properties files always use key=value format [OK]

Common Mistakes:

• Using colon instead of equals sign
• Using arrow symbols which are invalid
• Mixing YAML syntax with properties syntax

3. Given the following application.properties snippet:

spring.datasource.url=jdbc:mysql://localhost:3306/mydb
spring.datasource.username=root
spring.datasource.password=pass123

What is the effect of this configuration?

medium

A. It sets up a PostgreSQL database connection.

B. It configures a MySQL database connection with the specified URL and credentials.

C. It disables the datasource configuration.

D. It causes a syntax error and fails to start.

Solution

1. Step 1: Analyze the datasource properties

   The keys spring.datasource.url, username, and password configure the database connection details.

2. Step 2: Identify the database type and credentials

   The URL contains jdbc:mysql://, indicating a MySQL database with host localhost and database mydb. Username and password are set accordingly.

3. Final Answer:

   It configures a MySQL database connection with the specified URL and credentials. -> Option B

4. Quick Check:

   Datasource URL with jdbc:mysql = MySQL config [OK]

Hint: Look for jdbc:mysql in URL to identify MySQL config [OK]

Common Mistakes:

• Assuming PostgreSQL from MySQL URL
• Thinking this disables datasource
• Confusing syntax as error

4. You wrote this in application.properties:

server.port9090

Why does your Spring Boot app fail to start on port 9090?

medium

A. Spaces are not allowed anywhere in properties files.

B. Port 9090 is reserved and cannot be used.

C. Missing equals sign between key and value causes syntax error.

D. Property name is incorrect; should be server.port.number.

Solution

1. Step 1: Check properties file syntax

   Each line must have a key and value separated by an equals sign (=) or colon (:).

2. Step 2: Identify the missing equals sign

   The line server.port9090 lacks the equals sign, causing it to be parsed as a single key with no value and preventing the port from being set.

3. Final Answer:

   Missing equals sign between key and value causes syntax error. -> Option C

4. Quick Check:

   Properties need key=value format [OK]

Hint: Always use = or : between key and value [OK]

Common Mistakes:

• Omitting equals sign
• Using wrong property name
• Assuming spaces are forbidden everywhere

5. You want to migrate your Spring Boot app configuration from application.yml to application.properties. Which of the following is the correct way to convert this YAML snippet?

server:
  port: 9090
spring:
  datasource:
    url: jdbc:h2:mem:testdb
    username: sa
    password: ""

hard

A. server.port=9090
spring.datasource.url=jdbc:h2:mem:testdb
spring.datasource.username=sa
spring.datasource.password=

B. server.port : 9090
spring.datasource.url : jdbc:h2:mem:testdb
spring.datasource.username : sa
spring.datasource.password : ""

C. server.port => 9090
spring.datasource.url => jdbc:h2:mem:testdb
spring.datasource.username => sa
spring.datasource.password => ""

D. server.port9090
spring.datasource.urljdbc:h2:mem:testdb
spring.datasource.usernamesa
spring.datasource.password""

Solution

1. Step 1: Understand YAML to properties conversion

   YAML uses indentation and colons, while properties files use dot notation and equals signs.

2. Step 2: Convert nested YAML keys to dot notation with =

   The nested keys become dot-separated keys, and values are assigned with equals signs. Empty password is represented by an empty value.

3. Final Answer:

   server.port=9090 spring.datasource.url=jdbc:h2:mem:testdb spring.datasource.username=sa spring.datasource.password= -> Option A

4. Quick Check:

   YAML nesting = dot notation + = in properties [OK]

Hint: Convert YAML nesting to dot keys with = [OK]

Common Mistakes:

• Using colon instead of equals in properties
• Using arrows or spaces instead of =
• Not converting nested keys to dot notation