69 Spring Interview Questions and Answers

This document lists 69 common Spring interview questions with concise answers, aimed at Java backend developers preparing for interviews.

Framework Overview Spring is an open‑source Java enterprise application framework that simplifies development through Inversion of Control (IoC) and supports web, data‑access, and transaction features.

Benefits of Using Spring

Lightweight (core jar ~2 MB).

Inversion of Control for loose coupling.

Aspect‑Oriented Programming (AOP) to separate cross‑cutting concerns.

Container that manages object lifecycles and configuration.

Integrated MVC web framework.

Comprehensive transaction management (local and JTA).

Consistent exception handling.

Core Modules The framework is divided into modules such as Core, Bean, Context, Expression Language, JDBC, ORM, OXM, JMS, Transaction, Web, Web‑Servlet, Web‑Struts, and Web‑Portlet.

IoC Container and BeanFactory The BeanFactory (e.g., org.springframework.beans.factory.xml.XmlBeanFactory) creates and wires beans based on XML definitions. ApplicationContext extends BeanFactory and adds features like message source and web‑specific capabilities.

Dependency Injection (DI) DI can be performed via constructor injection or setter injection. Constructor injection is preferred for mandatory dependencies, while setter injection is suitable for optional ones.

Bean Scopes Spring supports several bean scopes: singleton (default), prototype, request, session, and global-session. Singleton beans are not thread‑safe by default.

Bean Lifecycle The lifecycle includes instantiation, property population, aware‑interface callbacks, BeanPostProcessor pre‑initialization, custom init methods or afterPropertiesSet, post‑initialization processing, and destruction callbacks.

Autowiring Five autowiring modes are available: no (manual), byName, byType, constructor, and autodetect. Limitations include the need for explicit configuration for complex cases and inability to autowire primitive types.

Annotations Common Spring annotations include @Configuration, @Bean, @Autowired, @Qualifier, @Required, and @Component. Annotation‑based configuration requires enabling <context:annotation-config/> in XML.

Data Access Spring simplifies JDBC via JdbcTemplate, provides DAO support, and integrates with ORM frameworks such as Hibernate, iBatis, JPA, TopLink, JDO, and OJB. Access to Hibernate can be achieved through HibernateTemplate, Callback, or extending HibernateDaoSupport.

Transaction Management Both programmatic and declarative transaction management are supported. Declarative management (using annotations or XML) is preferred for its non‑intrusive nature.

MVC Framework Spring MVC is built around DispatcherServlet and uses WebApplicationContext. Controllers are annotated with @Controller and request mappings are defined with @RequestMapping.

AOP Concepts AOP separates cross‑cutting concerns into aspects. Key terms include aspect, join point, pointcut, advice (before, after, after‑returning, after‑throwing, around), and proxy. Spring provides both XML‑based and annotation‑based ( @Aspect) aspect definitions.