Spring Interview Question and Answers

1) What is Spring Framework (Spring 6)?

Spring Framework is a comprehensive programming and configuration model for Java-based enterprise applications. As of Spring 6, it supports:

• Java 17+ as a baseline

• Jakarta EE 9 (e.g., jakarta.servlet instead of javax.servlet)

• Native support for GraalVM and AOT (Ahead-of-Time) compilation

• Enhanced observability and performance

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2) What are the advantages of Spring Framework 6?

• Loose Coupling & Dependency Injection (DI)

• Predefined Templates (JdbcTemplate, RestTemplate, etc.)

• Faster Development

• Declarative Programming (with annotations)

• Lightweight & Modular

• Native Compilation Support (via GraalVM)

• Better Observability (Micrometer support)

• Improved Testing Support

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3) What are the modules in Spring 6?

• Core Container: Beans, Core, Context, SpEL

• Data Access/Integration: JDBC, ORM, Transactions, JMS

• Web: Spring MVC, WebFlux (reactive)

• AOP, Aspects and Instrumentation

• Test: JUnit 5, Mockito, Spring TestContext

• Native: GraalVM and AOT support

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4) What is IoC and DI?

IoC (Inversion of Control) is a design principle where control of object creation is inverted to a container (Spring).
DI (Dependency Injection) is how Spring implements IoC.

Without DI:

class Employee {
    Address address = new Address(); // tightly coupled
}

With DI:

class Employee {
    Address address;
    public Employee(Address address) {
        this.address = address; // loosely coupled
    }
}

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5) What is the role of IoC Container in Spring?

The IoC container is responsible for:

• Creating objects

• Configuring them

• Wiring dependencies

• Managing lifecycle

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6) Types of IoC Containers in Spring:

• BeanFactory: Basic container

• ApplicationContext: More feature-rich, supports internationalization, AOP, etc.

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7) Difference: BeanFactory vs ApplicationContext

Feature	BeanFactory	ApplicationContext
Lazy Initialization	Yes	No (by default)
AOP Support	No	Yes
i18n Support	No	Yes
Event Propagation	No	Yes
Annotation Config	Limited	Full support

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8) Constructor vs Setter Injection

Criteria	Constructor Injection	Setter Injection
Partial Injection	Not possible	Possible
Overriding Values	No	Yes
Immutable Dependency	Yes	No
Use Case	Mandatory dependencies	Optional dependencies

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9) Autowiring in Spring

Autowiring automatically injects beans without manual configuration.

Modes:

Mode	Description
no	Default, no autowiring
byName	Matches bean by property name
byType	Matches bean by type
constructor	Injects using constructor

Note: XML-based autowiring is deprecated in favor of @Autowired, @Inject, @Qualifier.

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10) Bean Scopes in Spring 6

Scope	Description
singleton	Single shared instance (default)
prototype	New instance per request
request	One per HTTP request (web only)
session	One per HTTP session
application	One per ServletContext
websocket	One per WebSocket

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11) What is the default bean scope?

The singleton scope is the default.

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12) Are Singleton Beans Thread-Safe?

No, Spring singleton beans are not thread-safe by default. You must handle synchronization explicitly.

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13) What is Dependency Injection (DI)?

DI is a design pattern that promotes loose coupling by injecting dependencies into objects rather than letting objects construct their dependencies.

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14) What is a ViewResolver in Spring MVC?

A ViewResolver maps logical view names returned by controllers to actual views (e.g., JSPs, Thymeleaf, etc.).

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15) View Resolver Pattern

• Controller returns view name (e.g., "home")

• ViewResolver maps it to an actual view (/WEB-INF/views/home.jsp or home.html)

• Supports pluggable view technologies (JSP, Thymeleaf, PDF, Excel)

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16) Spring Transaction Management Types

1. Programmatic – using TransactionTemplate or PlatformTransactionManager

2. Declarative – using @Transactional

Declarative is recommended in most cases.

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17) Advantages of JdbcTemplate

• Reduces boilerplate code (no need to handle connection, statement, result set manually)

• Handles exceptions and resources automatically

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18) Key Classes in Spring JDBC API

• JdbcTemplate

• NamedParameterJdbcTemplate

• SimpleJdbcInsert

• SimpleJdbcCall

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19) How to fetch records using JdbcTemplate

Use query() method with:

• RowMapper: For row-wise mapping

• ResultSetExtractor: For custom extraction logic

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20) Advantage of NamedParameterJdbcTemplate

1. Improves readability using named parameters instead of ?, e.g.:

String sql = "SELECT * FROM users WHERE name = :name";

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21) What is the front controller in Spring MVC?

DispatcherServlet acts as the front controller that routes requests to appropriate controllers and views.

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22) What is AOP?

Aspect-Oriented Programming is a way to modularize cross-cutting concerns like logging, security, and transactions into reusable modules called aspects.

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23) Advantages of Spring AOP

• Modularizes repetitive concerns

• Reduces code duplication

• Dynamic proxy-based implementation

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24) Key AOP Terminology

Term	Description
JoinPoint	A point during execution (e.g., method call)
Advice	Action at a JoinPoint (e.g., before, after)
Pointcut	Expression to select JoinPoints
Aspect	Class with Advices and Pointcuts
Target	Actual object being advised
Proxy	Wrapper created to apply AOP
Weaving	Applying aspects to target objects