Application.properties basics in Spring Boot - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set the server port to 8080 in application.properties.

Spring Boot

server.[1]=8080

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

Aport

Bhost

Caddress

Durl

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'server.host' instead of 'server.port'

Using 'server.address' which is for IP binding

The property server.port sets the port number where the Spring Boot app listens.

2fill in blank

medium

Complete the code to set the application name to 'MyApp' in application.properties.

Spring Boot

spring.application.[1]=MyApp

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

Aname

Bversion

Cid

Dtitle

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'spring.application.version' which is for version info

Using 'spring.application.id' which is not standard

The property spring.application.name defines the app's name used in logs and discovery.

3fill in blank

hard

Fix the error in the property key to enable debug logging for Spring MVC.

Spring Boot

logging.level.[1]=DEBUG

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

Aspringframework.web

Borg.springframework.webmvc

Cspringframework

Dspringframework.webmvc.mvc

Attempts:

3 left

💡 Hint

Common Mistakes

Using too broad package like 'springframework'

Adding extra segments like 'mvc' twice

The correct package for enabling debug logs for Spring MVC is org.springframework.webmvc.

4fill in blank

hard

Fill both blanks to configure a datasource URL and username in application.properties.

Spring Boot

spring.datasource.[1]=jdbc:mysql://localhost:3306/mydb
spring.datasource.[2]=user123

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

Aurl

Bpassword

Cusername

Ddriver-class-name

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'password' instead of 'username' for the second blank

Using 'driver-class-name' for URL

spring.datasource.url sets the database URL, and spring.datasource.username sets the DB user.

5fill in blank

hard

Fill all three blanks to set server port, context path, and enable HTTPS in application.properties.

Spring Boot

server.[1]=8443
server.servlet.[2]=/app
server.ssl.[3]=true

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

Aport

Bcontext-path

Cenabled

Daddress

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'address' instead of 'port'

Using 'contextPath' instead of 'context-path'

Using 'enable' instead of 'enabled'

server.port sets the port, server.servlet.context-path sets the app path, and server.ssl.enabled enables HTTPS.

Practice

1. What is the primary purpose of the application.properties file in a Spring Boot project?

easy

A. To store configuration settings as key=value pairs

B. To write Java code for the application

C. To define HTML templates for the UI

D. To manage database schema migrations

Solution

1. Step 1: Understand the role of application.properties

   This file is used to store configuration settings in a simple key=value format.

2. Step 2: Compare with other options

   Writing Java code, defining HTML templates, or managing database migrations are done elsewhere, not in this file.

3. Final Answer:

   To store configuration settings as key=value pairs -> Option A

4. Quick Check:

   Config file = key=value pairs [OK]

Hint: Remember: properties file holds settings, not code or templates [OK]

Common Mistakes:

• Thinking it contains Java code
• Confusing it with HTML or template files
• Assuming it manages database migrations

2. Which of the following is the correct syntax to set the server port to 8081 in application.properties?

easy

A. server.port=8081

B. server-port: 8081

C. server_port=8081

D. port.server=8081

Solution

1. Step 1: Recall Spring Boot property syntax

   Spring Boot uses dot notation with key=value pairs in application.properties.

2. Step 2: Identify correct key for server port

   The correct key is server.port, and the value is set with an equals sign.

3. Final Answer:

   server.port=8081 -> Option A

4. Quick Check:

   Dot notation + equals sign = correct syntax [OK]

Hint: Use dot notation and equals sign for properties [OK]

Common Mistakes:

• Using underscores instead of dots
• Using colon instead of equals sign
• Swapping key parts order

3. Given this application.properties snippet:

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

What will Spring Boot do with these properties when the app starts?

medium

A. Create a new database named 'mydb'

B. Ignore these properties because they are invalid

C. Start a web server on port 3306

D. Connect to MySQL database at localhost with given credentials

Solution

1. Step 1: Identify datasource properties

   The keys starting with spring.datasource configure database connection details.

2. Step 2: Understand Spring Boot behavior

   Spring Boot uses these to connect to the specified MySQL database with username and password.

3. Final Answer:

   Connect to MySQL database at localhost with given credentials -> Option D

4. Quick Check:

   Datasource properties = DB connection [OK]

Hint: Datasource keys configure DB connection automatically [OK]

Common Mistakes:

• Thinking it starts a web server on DB port
• Assuming properties are ignored
• Believing it creates the database automatically

4. What is wrong with this application.properties line?

server.port-8080

medium

A. The port number 8080 is invalid

B. The key and value are separated by a dash instead of equals sign

C. The key should be port.server instead

D. There should be no spaces around the dash

Solution

1. Step 1: Check property syntax

   Properties require key and value separated by an equals sign (=), not a dash (-).

2. Step 2: Validate the key and value

   The key server.port is correct, and 8080 is a valid port number.

3. Final Answer:

   The key and value are separated by a dash instead of equals sign -> Option B

4. Quick Check:

   Use '=' to separate key and value [OK]

Hint: Always use '=' between key and value in properties [OK]

Common Mistakes:

• Using dash instead of equals sign
• Swapping key parts order
• Thinking spaces fix the syntax

5. You want to add a custom property app.title in application.properties and access it in your Spring Boot code. Which of these steps is correct?

hard

A. Add app.title=MyApp in properties and access it with System.getenv("app.title")

B. Add app.title: MyApp in properties and read it with System.getProperty("app.title")

C. Add app.title=MyApp in properties and use @Value("${app.title}") in code

D. Add app.title=MyApp in properties and use @Autowired String app.title in code

Solution

1. Step 1: Add custom property correctly

   Use key=value syntax: app.title=MyApp in application.properties.

2. Step 2: Access property in Spring Boot code

   Use @Value("${app.title}") annotation to inject the property value.

3. Final Answer:

   Add app.title=MyApp in properties and use @Value("${app.title}") in code -> Option C

4. Quick Check:

   Custom property + @Value injection = correct [OK]

Hint: Use @Value("${key}") to inject properties in code [OK]

Common Mistakes:

• Using colon instead of equals in properties
• Trying to get property from environment variables
• Incorrect use of @Autowired for simple values