Multi-module project structure in Spring Boot - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

How does a multi-module Spring Boot project handle dependencies?

Consider a multi-module Spring Boot project where module A depends on module B. What happens when you build module A?

A Module A can only use module B if both modules are merged into a single jar file.

B Module A ignores module B unless you manually copy module B's jar into module A's classpath.

C Module A must declare module B as a runtime dependency but not as a compile-time dependency.

D Module A automatically includes module B's classes and resources during its build and runtime.

💡 Hint

Think about how Maven or Gradle handles project dependencies in multi-module setups.

In a multi-module Spring Boot project, when module A declares a dependency on module B, the build system ensures that module B's classes and resources are available to module A both at compile time and runtime automatically.

📝 Syntax

intermediate

Correct parent POM declaration for multi-module Spring Boot project

Which of the following is the correct way to declare a parent POM for a multi-module Spring Boot project?

A

<parent>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-parent</artifactId>
  <version>2.5.0</version>
</parent>

B

<parent>
  <groupId>com.example</groupId>
  <artifactId>parent-project</artifactId>
  <version>1.0.0</version>
</parent>

C

<parent>
  <groupId>com.example</groupId>
  <artifactId>parent-project</artifactId>
  <version>1.0.0</version>
  <scope>compile</scope>
</parent>

D

<parent>
  <groupId>com.example</groupId>
  <artifactId>child-module</artifactId>
  <version>1.0.0</version>
</parent>

💡 Hint

The parent POM should represent the overall project, not a child module.

The parent POM declaration must point to the parent project artifact, not a child module. Scope is not valid inside <parent> tag.

🔧 Debug

advanced

Why does a Spring Boot multi-module project fail to start with NoSuchBeanDefinitionException?

You have a multi-module Spring Boot project. Module A defines a service bean, and module B depends on module A. When running module B, you get NoSuchBeanDefinitionException for the service in module A. What is the most likely cause?

A Module B does not have module A as a dependency in its build configuration.

B The service bean in module A is not annotated with <code>@Service</code> or <code>@Component</code>.

C Module B's <code>@SpringBootApplication</code> scan does not include module A's packages.

D Module A's service bean is defined as <code>private</code> and cannot be accessed.

💡 Hint

Think about how Spring Boot scans for beans in multi-module projects.

Spring Boot scans for beans starting from the package of the class annotated with @SpringBootApplication. If module B's main class is in a package that does not include module A's packages, Spring will not find the beans defined there.

❓ state_output

advanced

What is the output when running a multi-module Spring Boot project with conflicting properties?

In a multi-module Spring Boot project, module A and module B both define application.properties files with the same property app.name but with different values. When running the project, which value will Spring Boot use?

A The value from the module that appears last in the classpath is used.

B The value from module A's <code>application.properties</code> is used.

C Spring Boot merges both and throws an error due to conflict.

D The value from module B's <code>application.properties</code> is used.

💡 Hint

Consider how Spring Boot loads properties from multiple sources.

Spring Boot loads properties from all application.properties files found in the classpath. When the same property is defined multiple times, the last one loaded (usually the one appearing last in the classpath order) overrides the previous ones.

🧠 Conceptual

expert

Best practice for sharing common code in multi-module Spring Boot projects

In a large multi-module Spring Boot project, you want to share common utility classes and configurations across multiple modules. What is the best practice to organize this?

A Create a separate common module that contains shared code and declare it as a dependency in other modules.

B Duplicate the common code in each module to avoid dependency issues.

C Place all common code in the parent POM file as Java classes.

D Use Spring Boot's auto-configuration to automatically share code without dependencies.

💡 Hint

Think about modular design and code reuse principles.

Creating a separate common module for shared code is a standard practice. It allows clean separation, easier maintenance, and clear dependency management. Duplicating code leads to maintenance problems. The parent POM cannot contain Java classes. Auto-configuration helps but does not replace module dependencies.