Answers to 10 Spring Interview Questions
how do you define spring framework? what are its major components?
Spring is likely the most popular Java framework for creating simple web applications, enterprise-level cloud applications, and microservices. Spring provides comprehensive infrastructure support for application development with complex requirements and designs.
The Spring framework handles infrastructure (via dependency injection), allowing us to concentrate on the application's core functionality. Spring framework contains formalized design patterns as first-class objects, which we can integrate into our application(s) without worrying too much about their backend functionality.
The Spring Framework is composed of individual modules. Depending on the functionality they require, applications can select the modules they need.
As illustrated in the following diagram, Spring modules are categorized as Core Container, Data Access/Integration, WebMVC, AOP (Aspect Oriented Programming), Instrumentation, Messaging, Testing, and others.
what are the spring framework's advantages?
The following is a subset of the advantages of using Spring Framework.
- — Using the Dependency Injection (DI) pattern, application dependencies are declared and managed explicitly.
- — Compared to EJB containers, IoC containers are typically more lightweight. This is beneficial for developing and deploying Spring applications on machines with limited memory and CPU resources.
- — Spring does not reinvent the wheel; rather, it uses existing technologies such as multiple ORM frameworks, logging frameworks, JMS, and view technologies.
- Spring is organized in a modular fashion, so even though the number of packages and classes is substantial, we only need to be concerned with the dependencies we need and can ignore the rest.
- — The environment-dependent code of a Spring application is managed by the framework, making its testing simple. In addition, using POJOs modeled after Java beans makes it simpler to inject test data via dependency injection.
- — Spring's web framework is a well-designed web MVC framework that offers an excellent alternative to web frameworks such as Struts and other over-engineered or less popular web frameworks.
- — Spring provides a consistent transaction management interface that can scale down to a local transaction (using a single database, for instance) and up to global transactions (using JTA, for example).
What are Dependency Injection (DI) and Inversion of Control (IoC)?
In software engineering, inversion of control (IoC) is a programming technique in which object coupling is bound at run time by an assembler object and is typically unknown at compile time through static analysis.
In conventional programming, the flow of business logic is determined by objects that are statically assigned to each other.
Using inversion of control, the application flow is dependent on the object graph instantiated by the assembler and is enabled by object interactions defined through abstractions. "dependency injection" is used to accomplish the binding process.
Inversion of control is a design paradigm used to give more control to the components of an application that are actually performing the work.
Dependency injection is a design pattern used to create instances of objects on which other objects depend without knowing at compile time which class will provide that functionality.
Inversion of control is dependent on dependency injection because a mechanism is required to activate the components that provide the specific functionality. If the framework is no longer in charge, how will it know which components to create?
Spring allows for the following methods of dependency injection:
- Constructor injection, Setter injection, Fields Injection
Explain Spring Framework's Inversion of Control.
In the spring framework, inversion of control refers to the capability of the framework to create, destroy, and manage the beans' lifecycle.
Spring's inversion of control is centered on the ApplicationContext (which uses the BeanFactory internally).
The Spring bean factory assembles beans using configuration metadata, which can take the form of XML configuration or annotations.
What's the distinction between BeanFactory and ApplicationContext?
A BeanFactory is comparable to a factory class that stores a collection of beans. BeanFactory stores bean definitions within itself and instantiates a bean whenever a client requests one.
BeanFactory is capable of establishing associations between cooperating beans as they are instantiated. BeanFactory participates in the life cycle of the beans by invoking initialization and destruction methods.
Application context and bean factory are equivalent at a high level. Both load bean definitions, link beans together, and dispense beans upon demand. In addition, the application context offers:
- — A method for resolving text messages, which includes support for internationalization.
- — A standard method for loading file resources.
- — Events sent to beans registered as listeners.
How Many Ways Can Spring Be Configured for Our Applications?
There are three ways to configure Spring in applications:
- — Annotation-based configuration
- — Java-based configuration
- — XML based configuration
What is Spring Configuration XML?
External configuration files, typically in XML format, are used to specify Spring framework's required dependencies and services. These XML configuration files typically begin with the beans> tag and include numerous bean definitions AND application-specific configuration options.
Spring XML Configuration's primary objective is to configure all Spring components with XML files.
This indicates that no other Spring Configuration will be present (like annotations or configuration via Java classes).
A Spring XML Configuration uses Spring namespaces to make the sets of XML tags used in the configuration accessible; the primary Spring namespaces are context, beans, JDBC, TX, AOP, MVC, etc.
What is Java-based Spring Configuration?
@Configuration annotated classes and @Bean annotated methods form the core of Spring's java-configuration support.
The @Bean annotation indicates that a method creates, configures, and initializes a new object managed by the Spring IoC container. The @Bean annotation provides the same functionality as the <bean/> element.
Annotating a class with @Configuration signifies that its primary function is to provide bean definitions. In addition, @Configuration classes permit inter-bean dependencies to be defined by calling other @Bean methods within the same class.
What precisely is Annotation-based Configuration?
Beginning with Spring 2.5, dependency injection could be configured using annotations. Therefore, instead of using XML to describe a bean's wiring, we can move the bean configuration directly into the component class by using annotations on the relevant class, method, or field declaration.
Annotation injection occurs prior to XML injection; therefore, the XML configuration will supersede the annotation configuration when beans are wired using both approaches.
Spring's default configuration does not include annotation wiring. Therefore, prior to utilizing annotation-based wiring, we must enable it in our Spring configuration file.
Describe the life cycle of Spring Bean.
It is simple to comprehend the life cycle of a Spring bean. When a bean is instantiated, it may be required to perform some initialization in order to be in a usable state. Similarly, spring context may necessitate cleanup when the bean is no longer required and the container is discarded.
The spring bean factory is in charge of managing the life cycle of beans produced in spring containers. The life cycle of beans consists of call back methods that can be categorized broadly into two groups:
- 1-) Post initialization call back methods
- 2-) Pre destruction call back methods
Spring framework offers the following four options for controlling bean life cycle events:
- — InitializingBean and DisposableBean callback interfaces
- — Other Aware interfaces for specific behavior
- — Custom init() and destroy() methods in bean configuration file
- — @PostConstruct and @PreDestroy annotations