Project structure walkthrough in Spring Boot - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What is the purpose of the 'src/main/resources' folder in a Spring Boot project?

In a typical Spring Boot project, what kind of files do you place inside the 'src/main/resources' folder?

A Java source code files that contain the main application logic.

B Test source code files for unit and integration tests.

C Configuration files, static assets, and templates used by the application.

D Compiled class files generated after building the project.

💡 Hint

Think about where you keep files like application.properties or HTML templates.

The 'src/main/resources' folder holds non-code files like configuration, static files, and templates that the application uses at runtime.

❓ component_behavior

intermediate

What happens if you place a Java class outside 'src/main/java' in a Spring Boot project?

Consider a Java class placed in 'src/test/java' instead of 'src/main/java'. What is the effect on the Spring Boot application?

A The class will only be compiled and used during testing, not in the main application runtime.

B The class will be included in the main application build and run normally.

C The class will cause a build failure due to incorrect folder placement.

D The class will be ignored completely and not compiled or used anywhere.

💡 Hint

Think about the difference between main and test source folders.

Classes in 'src/test/java' are compiled and used only for testing, not included in the main application runtime.

📝 Syntax

advanced

Which folder should you place your Spring Boot controller classes in for proper component scanning?

Given a Spring Boot project with base package 'com.example.app', where should controller classes be placed to be detected automatically?

A com.example.app.services inside 'src/main/resources'

B com.example.controllers outside the base package

C com.example.app.controllers inside 'src/test/java'

D com.example.app.controllers inside 'src/main/java'

💡 Hint

Controllers must be inside the base package or its subpackages.

Spring Boot scans the base package and its subpackages for components like controllers. Placing them inside 'com.example.app.controllers' ensures detection.

🔧 Debug

advanced

Why does Spring Boot fail to find your application.properties file?

You placed your application.properties file in 'src/main/java' instead of 'src/main/resources'. What will happen when you run the app?

A The application will crash with a FileNotFoundException.

B Spring Boot will fail to load the properties file because it only looks in 'src/main/resources'.

C The application.properties file will be ignored but no error will occur.

D Spring Boot will load the properties file without any issues.

💡 Hint

Where does Spring Boot expect configuration files to be?

Spring Boot loads configuration files from the classpath, which includes 'src/main/resources' but not 'src/main/java'. Placing the file in the wrong folder means it won't be found.

❓ lifecycle

expert

What is the role of the 'META-INF' folder inside 'src/main/resources' in a Spring Boot project?

You find a 'META-INF' folder inside 'src/main/resources'. What is its typical purpose in a Spring Boot application?

A It holds metadata files like 'MANIFEST.MF' that describe the packaged jar.

B It stores static web assets like CSS and JavaScript files.

C It contains compiled Java bytecode for the application.

D It contains test reports generated after running tests.

💡 Hint

Think about what metadata about the jar or application might be stored.

The 'META-INF' folder contains metadata files such as 'MANIFEST.MF' that describe the jar file and its contents, important for packaging and deployment.

Practice

1. In a typical Spring Boot project, where should you place your main application Java files?

easy

A. src/resources/java

B. src/main/resources

C. src/test/java

D. src/main/java

Solution

1. Step 1: Understand Spring Boot folder roles

   The src/main/java folder is for main Java source code including the application entry point.

2. Step 2: Identify correct folder for main Java files

   Main application files should not be in resources or test folders, so src/main/java is correct.

3. Final Answer:

   src/main/java -> Option D

4. Quick Check:

   Main Java code = src/main/java [OK]

Hint: Main Java code always goes under src/main/java [OK]

Common Mistakes:

• Confusing resources folder with Java source folder
• Placing main code in test folder
• Using incorrect folder names like src/resources/java

2. Which file is commonly used to manage dependencies and build steps in a Spring Boot Maven project?

easy

A. pom.xml

B. application.properties

C. build.gradle

D. settings.xml

Solution

1. Step 1: Identify build tool for Maven projects

   Maven uses pom.xml to manage dependencies and build configuration.

2. Step 2: Differentiate from Gradle and config files

   build.gradle is for Gradle, application.properties is for app config, and settings.xml is not for dependencies.

3. Final Answer:

   pom.xml -> Option A

4. Quick Check:

   Maven build file = pom.xml [OK]

Hint: Maven uses pom.xml; Gradle uses build.gradle [OK]

Common Mistakes:

• Confusing application.properties with build files
• Mixing Gradle and Maven build files
• Thinking settings.xml manages dependencies

3. Given this Spring Boot project structure snippet, where will the test Java files be located?

src/
  main/
    java/
    resources/
  test/
    java/
    resources/

medium

A. src/main/resources

B. src/test/java

C. src/main/java

D. src/test/resources

Solution

1. Step 1: Understand test folder purpose

   The src/test/java folder is for Java test source files.

2. Step 2: Identify test Java files location

   Test Java files go under src/test/java, not in main or resources folders.

3. Final Answer:

   src/test/java -> Option B

4. Quick Check:

   Test Java code = src/test/java [OK]

Hint: Test Java files go in src/test/java folder [OK]

Common Mistakes:

• Putting test Java files in src/main/java
• Confusing test resources with test Java code
• Using src/main/resources for tests

4. You accidentally placed your application.properties file inside src/main/java. What problem will this cause?

medium

A. The application will fail to start due to missing config

B. The build will fail with a syntax error

C. The properties file will be ignored and default config used

D. The application.properties will be loaded correctly anyway

Solution

1. Step 1: Know where Spring Boot loads config files

   Spring Boot loads application.properties from src/main/resources or classpath root.

2. Step 2: Effect of wrong file location

   If placed in src/main/java, it won't be found and ignored, so defaults apply.

3. Final Answer:

   The properties file will be ignored and default config used -> Option C

4. Quick Check:

   Config files must be in resources, else ignored [OK]

Hint: Config files must be in resources folder to load [OK]

Common Mistakes:

• Assuming app fails to start immediately
• Thinking build fails due to config file location
• Believing misplaced properties still load

5. You want to add a new configuration file for your Spring Boot app that should be packaged inside the jar and accessible at runtime. Where should you place this file?

hard

A. src/main/resources/config

B. src/main/java/config

C. src/test/resources/config

D. src/main/resources/static

Solution

1. Step 1: Understand resource packaging in Spring Boot

   Files in src/main/resources are packaged inside the jar and available at runtime.

2. Step 2: Choose correct folder for config files

   Config files should be under src/main/resources/config to be included and organized.

3. Final Answer:

   src/main/resources/config -> Option A

4. Quick Check:

   Runtime config files go in src/main/resources [OK]

Hint: Put runtime config files in src/main/resources folder [OK]

Common Mistakes:

• Placing config files in src/main/java which is for code
• Using test resources folder which is not packaged
• Putting config in static folder meant for web assets