Spring Interview Question and Answers for fresher and experienced part 2 | Code Decode

Summary

The video covers the basics of the Spring Framework, its importance in the IT industry, and how legacy Java projects can be converted to Spring. It dives into Inversion of Control (IoC) containers, specifically ApplicationContext and BeanFactory, explaining how POJOs (Plain Old Java Objects) are converted into Spring Beans. The tutorial also demonstrates dependency injection through both setter and constructor methods. Additionally, the video explains the configuration metadata options—XML-based, annotation-based, and Java configuration-based—highlighting their performance trade-offs, and concludes with the differences between ApplicationContext and BeanFactory.

Takeaways

• 📝 Spring is crucial in the IT industry due to its unique features and modular structure.
• 🔄 Many MNCs are migrating legacy Java projects to Spring for better structure and functionality.
• 💡 Inversion of Control (IoC) is a core concept in Spring that helps convert Java POJOs into Spring beans.
• ⚙️ There are three methods for providing configuration metadata in Spring: XML-based, annotation-based, and Java configuration-based.
• 📂 XML and Java-based configuration provide higher performance and readability but are more redundant compared to annotation-based methods.
• 🛠 Annotation-based configuration reduces time and redundancy but may lower performance due to component scanning across multiple packages.
• 🚀 Spring has two primary containers: ApplicationContext and BeanFactory, each with different methods for managing beans.
• ⚡ ApplicationContext eagerly loads beans, while BeanFactory uses lazy loading, instantiating beans only when needed.
• 🔗 There are two types of dependency injection in Spring: constructor injection and setter injection, both demonstrated with examples.
• 🌍 ApplicationContext supports internationalization, while BeanFactory does not, making ApplicationContext more suitable for global applications.

Q & A

What are the main features that make Spring important in the IT industry?

Spring provides dependency injection, aspect-oriented programming, and modularity, making it easier to develop and manage large-scale applications in the IT industry.

What does IoC (Inversion of Control) mean in the Spring framework?

Inversion of Control (IoC) in Spring refers to the container managing the control of object creation, configuration, and dependency injection, instead of the objects controlling these tasks themselves.

How do many companies convert legacy Java projects into Spring-based projects?

Companies often inject dependencies into legacy Java projects, such as converting simple POJOs (Plain Old Java Objects) and integrating them with Spring using components and annotations for dependency management.

What is the purpose of configuration metadata in Spring, and what are the three ways to provide it?

Configuration metadata tells the Spring container how to create and configure beans. It can be provided in three ways: XML-based configuration, annotation-based configuration, and Java configuration-based.

What is the key difference between XML and annotation-based configuration in Spring?

XML-based configuration centralizes bean definitions in a single file, enhancing performance and readability, but is more tedious due to redundancy. Annotation-based configuration is faster and reduces redundancy but can lower performance due to component scanning.

What are the two types of containers in Spring, and how do they differ?

The two types of containers in Spring are ApplicationContext and BeanFactory. ApplicationContext eagerly loads all beans during startup and supports internationalization, whereas BeanFactory is lazy-loaded and instantiates beans only when they are requested.

How does setter injection differ from constructor injection in Spring?

Setter injection injects dependencies via setter methods, whereas constructor injection injects them through the constructor at the time of object creation. Both are ways to perform dependency injection in Spring.

What happens when annotations are removed from a Spring class?

If annotations are removed from a Spring class, the container will no longer recognize the class as a bean unless alternative configuration, such as XML-based or Java-based configuration, is provided.

What is lazy loading in Spring, and how is it applied in BeanFactory?

Lazy loading in Spring means that beans are not instantiated until they are requested. In BeanFactory, beans are lazily loaded, meaning they only get instantiated when the `getBean` method is called.

Why is ApplicationContext preferred over BeanFactory in certain cases?

ApplicationContext is preferred over BeanFactory when features like eager loading, internationalization, event propagation, and annotation-based configurations are needed, which BeanFactory does not support.