Best 50+ Java Spring Interview Questions with Answers

Spring Interview Questions

The following are the Spring Interview Questions which discuss the top 50+ questions with proper explanation. 

What is a spring?

A spring is a framework designed to assist Java programmers in developing code. It offers features such as an IOC (Inversion of Control) container, a Dependency Injector, an MVC (Model-View-Controller) flow, and numerous other APIs tailored to Java developers.

What are Advices in Spring? 

Execution of an aspect can be likened to a performance on a stage. An advice serves as a method of teaching your application a new skill. These teachings are typically introduced at specific moments known as “joinpoints.”

What is the default scope of bean in the Spring framework?

In the Spring framework, beans are the fundamental building blocks of an application, representing various components and services. The term “scope” refers to the lifecycle and visibility of a bean within the Spring container. Among the different scopes available, the default scope is Singleton. When a bean is configured with Singleton scope, a single instance of that bean is created and shared throughout the entire application context.

This means that every time the application requests the creation of a bean with Singleton scope, the Spring container provides the same instance, promoting efficient resource utilization and maintaining consistency across the application. However, developers should be cautious when using Singleton scope for beans that require unique states or concurrent access, as the shared instance might lead to unintended side effects. For scenarios where distinct instances are needed, developers can explicitly configure beans with other scopes such as Prototype, Request, Session, or Custom scopes to suit the specific requirements of their application.

Name the types of transaction management that are supported by Spring?

Spring supports two main types of transaction management:

• Declarative Transaction Management: This approach involves configuring transactions through XML configuration or annotations. Developers specify the transactional behavior for methods or classes using metadata, and Spring automatically manages the transactions accordingly. It offers a more concise and modular way of handling transactions, separating the transactional concerns from the business logic.

• Programmatic Transaction Management: In this approach, developers explicitly manage transactions within the application code using Spring’s transaction management APIs. They have full control over when to start, commit, or roll back transactions. While it provides more fine-grained control, it can also result in more verbose code and a mixing of transactional and business logic.

Both approaches have their merits and are suitable for different scenarios. Declarative transaction management is often preferred for its cleaner separation of concerns and reduced boilerplate code, while programmatic transaction management might be used when specific transaction handling is required or in legacy applications.

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Are Singleton beans are a thread-safe in Spring Framework? 

Singleton beans are not inherently thread-safe in the Spring framework. While a singleton bean ensures that there is only one instance of the bean in the application context, it doesn’t guarantee thread safety by default. If multiple threads concurrently access and modify the state of a singleton bean without proper synchronization, it can lead to data inconsistencies and unexpected behavior.

Developers should take appropriate measures, such as using synchronized blocks or employing thread-safe classes and techniques, to ensure the thread safety of singleton beans when needed. Additionally, consider using other bean scopes, like prototype, in scenarios where thread safety is a primary concern.

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What are the benefits of the Spring Framework? 

The Spring framework offers a range of benefits, including:

• Component-Centric Approach: The framework promotes the use of components extensively.
• Enhanced Reusability: It supports increased code reuse.
• Effective Decoupling: Spring facilitates loose coupling between components.
• Efficient Coding: By implementing design patterns like singleton, factory, and service locator, it reduces coding efforts.
• Elimination of Resource Leaks: Spring helps prevent resource leakage issues.
• Declarative Transaction Management: It provides a declarative way to manage transactions.
• Seamless Integration: Spring easily integrates with various third-party tools and technologies.”

What is Bean Factory? 

The Bean Factory serves as the fundamental component within the Spring framework. It functions as a lightweight container responsible for loading bean definitions and overseeing bean management. These beans are configured through XML files and primarily manage singleton-defined instances. Furthermore, the Bean Factory takes charge of lifecycle methods and the injection of dependencies. Additionally, it plays a role in eliminating ad hoc singletons and factories.

Define Bean Wiring.

Bean wiring refers to the process of establishing connections or relationships between various application components, specifically the beans within a Spring container. This enables these beans to interact and collaborate effectively within the Spring framework.

 

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What is called Spring MVC? 

Spring MVC, or Spring Model-View-Controller, refers to a singular shared controller instance that manages request-type controllers and interceptors within the Inversion of Control (IoC) container. This architecture supports the utilization of multiple Dispatcher Servlets, enabling them to share the application context interface while maintaining separation in the class-based interface.

 

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What are the various event types associated with Listeners? 

 

The following represent the diverse event types for listeners:

1. ContextClosedEvent: Triggered upon the closure of the context.
2. ContextRefreshedEvent: Fired during the initialization or refreshment of the context.
3. RequestHandledEvent: Activated when the web context manages a request.

 

Differentiate between singleton and prototype bean

Singleton Bean: A singleton bean in Spring refers to a scenario where only one instance of the bean is created within the application context. This single instance is shared among all the requesting components. Any subsequent requests for that bean will result in the same instance being returned. Singleton beans are suitable for stateless objects or when a single shared instance is desired for efficiency.

Prototype Bean: On the other hand, a prototype bean involves creating a new instance of the bean for each request made to the Spring container. This means that every time a component requests the prototype bean, a distinct instance is returned. Prototype beans are ideal for stateful objects or scenarios where diverse instances are required, ensuring independence and isolation.

 

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What are the Varieties of Dependency Injection? 

 

The Spring framework facilitates two primary forms of dependency injection:

1. Setter Injection
2. Constructor Injection

 

Write about the Core container module? 

At the heart of the Spring framework lies the core container module, which forms the foundation for its fundamental functionalities. Serving as the cornerstone of the entire Spring framework, this module is pivotal in shaping its architecture and capabilities.

What is the AOP module? 

The AOP module within the Spring framework is tailored for applications that leverage Spring’s capabilities. It incorporates support from the AOP Alliance to establish seamless compatibility between Spring and alternative AOP frameworks.

This module guides Spring in introducing annotations into the source code, elucidating how aspects should be implemented and applied.

What is AOP Alliance? 

The AOP Alliance represents an open-source initiative designed to encourage the widespread utilization of Aspect-Oriented Programming (AOP). Its primary objective is to establish a unified collection of components and interfaces, fostering enhanced interoperability across diverse AOP implementations.

What is called the spring configuration file? 

The Spring configuration file, commonly referred to as the “Spring configuration file,” is an XML document that contains organized information. This file outlines the configuration and interaction details among various classes within the Spring framework.

 

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What are the different types of Autowire? 

 

The Spring framework offers four distinct autowiring options:

• byName
• byType
• constructor
• autodetect

 

What are the types of transaction management that are supported by spring? 

Spring provides support for two main types of transaction management:

1. Declarative Transaction Management
2. Programmatic Transaction Management

 

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When are declarative and programmatic transaction management used? 

Programmatic transaction management is recommended when dealing with a limited number of transactional operations. On the other hand, for handling a substantial volume of transactional operations, declarative transaction management is the preferred approach.

Why the Spring framework is needed? 

The Spring framework is indispensable due to its:

• Lightweight Container: It offers a remarkably lightweight container.
• Framework Features: It provides comprehensive framework functionalities.
• Inversion of Control (IoC): Spring facilitates the Inversion of Control principle.
• Aspect-Oriented Programming (AOP): It supports Aspect-Oriented Programming capabilities.

Name the various modules used in the spring framework.

List of Modules Utilized in the Spring Framework:

• AOP Module (Aspect Oriented Programming)
• JDBC Abstraction and DAO Module
• Core Container Module
• MVC Framework Module
• Application Context Module
• Object/Relational (O/R) Mapping Integration Module
• Web Module

 

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Explain the RowCallbackHandler in Spring.

The RowCallbackHandler within the Spring framework serves the purpose of being invoked for every individual row contained within a ResultSet. Its main function revolves around the extraction of values from the ResultSet.

Define Application context module

The Application Context module holds significant importance as it furnishes essential services such as EJB integration, remoting, JNDI access, and scheduling. It elevates Spring to the status of a comprehensive framework. Furthermore, it expands upon the concept of BeanFactory through the implementation of lifecycle events, support for internationalization messages, and validation.

Write about the AOP module.

The Aspect-Oriented Programming (AOP) module within the Spring framework provides a powerful and flexible way to address cross-cutting concerns in your application. Cross-cutting concerns are aspects of your software that affect multiple parts of your codebase, such as logging, security, and transaction management. AOP allows you to modularize and manage these concerns separately from the main business logic, promoting better code organization and maintainability.

 

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What is a BeanFactory Interface? 

The BeanFactory interface is a core component of the Spring Framework that serves as a central registry for managing and providing instances of beans within an application. It acts as a container for holding various bean definitions, enabling the creation, configuration, and retrieval of bean instances based on these definitions. The BeanFactory interface forms the foundation for the broader application context in Spring, offering essential functionalities for inversion of control (IoC) and dependency injection, which are fundamental principles of the framework’s design philosophy.

State the differences between ApplicationContext and BeanFactory in spring.

Comparison between ApplicationContext and BeanFactory in Spring:

• Initialization: ApplicationContext initializes beans eagerly, while BeanFactory initializes beans lazily.
• Bean Post-Processing: ApplicationContext supports automatic bean post-processing, whereas BeanFactory does not provide advanced support for it.
• Resource Loading: ApplicationContext offers enhanced resource loading capabilities, including internationalization and event propagation. BeanFactory has basic resource capabilities.
• AOP Support: ApplicationContext includes built-in support for aspect-oriented programming (AOP), while BeanFactory requires additional configuration for AOP.
• Integration: ApplicationContext provides integration with various enterprise services like EJB, whereas BeanFactory focuses primarily on bean instantiation and management.
• Customization: ApplicationContext allows easier extension through the HierarchicalApplicationContext class, which supports parent-child relationships for contexts. BeanFactory does not inherently support this feature.

What is Auto Wiring? 

Auto-wiring is a feature in the Spring framework that allows you to automatically inject dependencies into Spring beans without explicitly specifying the wiring details in the XML configuration or Java code. In other words, Spring can automatically detect the dependencies a bean needs and provide them at runtime.

Auto-wiring simplifies the configuration process and reduces the need for manual wiring of dependencies, making the codebase more concise and maintainable.

What are the different Modes of Autowiring? 

Autowiring in Spring operates through five distinct modes:

• No Autowiring (no): No automatic wiring is performed.
• Autowiring by Name (byName): Wiring is based on the property names.
• Autowiring by Type (byType): Wiring is determined by property types.
• Constructor Autowiring (constructor): Similar to byType, but applied within the constructor.
• Autowire Detection (autodetect): Spring autonomously selects between byType and constructor-based autowiring.

How to start using spring? 

To embark on your Spring journey, follow these steps:

• Download Spring and Dependencies: Begin by downloading the necessary Spring framework and its associated files from the official Spring website.

• Create Application Context XML: Construct an application context XML file. This document will define the beans (components) you intend to use and establish their interdependencies.

• Integrate XML with web.xml: Integrate your application context XML file with the web.xml configuration of your project. This step ensures proper coordination between your Spring-defined beans and your web application.

• Deploy and Run: Finally, deploy your application. Execute it to witness your Spring-powered components in action.

What are the methods of the bean life cycle? 

The life cycle of a bean involves two crucial stages:

• Initialization: This stage includes the “Setup” method, which is invoked when the bean is being loaded into the container.

• Destruction: The “Teardown” method is called when the bean is being unloaded from the container.

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What is IOC? 

Inversion of Control (IoC), also referred to as the dependency injection pattern, involves a shift in how object creation is managed. Rather than programmers directly creating objects, IoC designates this responsibility to an assembler. The assembler then handles the instantiation of necessary classes as required within this design pattern.

Write about the different types of Listener related events.

Various Types of Listener-Related Events:

• ContextRefreshedEvent: This event is triggered upon the refresh or initialization of the context.
• RequestHandledEvent: When the web context is actively processing a request, this event is invoked.
• ContextClosedEvent: Whenever the context is closed, this event is fired.

What is Aspect? 

An aspect, often referred to as logging, plays a vital role across the entire application. It represents a cross-cutting feature within an application through Aspect-Oriented Programming (AOP).

 

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What is Joinpoint? 

A joinpoint refers to a specific moment within an application where an aspect can be seamlessly integrated. This juncture could encompass various scenarios such as the alteration of a field, the invocation of a method, or the occurrence of an exception. Within these instances, additional code from a new aspect can be introduced to imbue the application with fresh behaviors.

At this juncture, the aspect’s code can be seamlessly woven into the standard flow of the application, allowing for a modification of the existing behavior.

What is called Advice? 

“Advice” refers to the implementation of an aspect in an application. It introduces new behavior to the application and is injected into the codebase at specific points called joinpoints.

In essence, advice serves as a way to convey fresh functionality to your application. Typically, this advice is integrated into the application precisely at the joinpoints.

What is a Pointcut? 

A pointcut defines specific locations or conditions within a program’s execution flow where advice, such as additional functionality or behavior, can be applied.

What is weaving? 

Weaving involves the creation of a fresh proxy object by applying aspects to the target object.

What is the difference between singleton and prototype bean? 

• Singleton Bean: A singleton bean corresponds to a solitary object instance within the Spring IOC container. This means that only one instance of the bean is created and shared across the entire container.

  Prototype Bean: In contrast, a prototype bean associates a single bean definition with the potential to generate multiple object instances within the Spring IOC container. With a prototype bean, you can create any number of instances, each separate from the others, as per your requirements.

In what points can weaving be applied? 

Weaving can be applied in the following contexts:

• Compile Time: Weaving can be performed during the compilation process.
• Class Load Time: Weaving can take place during the loading of classes.
• Runtime: Weaving can also be applied dynamically during program execution.

What are the different types of AutoProxying? 

There are various forms of AutoProxying available, including:

• BeanNameAutoProxyCreator
• DefaultAdvisorAutoProxyCreator
• Metadata-based AutoProxying

These different AutoProxying methods serve distinct purposes within the Spring Framework.

How can beans be made singleton or prototype? 

Beans can be configured as singleton or prototype using the ‘singleton’ attribute within the bean tag. When the attribute is set to ‘TRUE’, the bean functions as a singleton; otherwise, it operates as a prototype.

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What classes are used to control the database connection? 

Here is a list of classes dedicated to controlling database connections:

• DataSourceUtils
• SmartDataSource
• AbstractDataSource
• SingleConnectionDataSource
• DriverManagerDataSource
• TransactionAwareDataSourceProxy
• DataSourceTransactionManager

Describe DAO in Spring framework.

DAO, which stands for Data Access Object, serves as a bridge between Java’s database connectivity and Object-Relational Mapping (ORM) entities. In Spring, the DAO is a fundamental component that facilitates connections with various data sources such as JDBC, Hibernate, JDO, JPA, Common Client Interface, and Oracle databases. It plays a crucial role in abstracting the underlying data access complexity and enables efficient interaction with databases and persistence layers.

What is Autoproxying? 

Autoproxying in Spring involves the automatic generation of proxies for Spring users. This functionality is supported through the following two classes:

• BeanNameAutoProxyCreator: This class facilitates the automatic creation of proxies based on bean names.

• DefaultAdvisorAutoProxyCreator: This class is responsible for the automatic proxy creation using advisors.

These classes enable Spring to generate proxies seamlessly, enhancing the framework’s capabilities for users.

What is Metadata Autoproxying? 

Metadata Autoproxying is a technique within the Spring Framework that leverages metadata to guide its operation. This process is influenced by source-level attributes, effectively encapsulating metadata within the source code itself. By centralizing metadata in a single location, this approach is primarily employed to facilitate declarative transaction support.

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What is ‘Throws advice’ in Spring? 

In Spring, ‘Throws Advice’ addresses exception handling behavior. It is an interface that doesn’t require explicit method implementations.

For a class to implement this interface, it should possess a method with the following signature:

1. void sampleThrow(Throwable ex)
2. void sampleThrow(Method method, Object[] args, Object target, Throwable ex)

What are the various editors used in spring work? 

The Spring Framework offers a range of custom editors, including:

• PropertyEditor: Manages property editing and type conversion.
• URLEditor: Handles URL type conversion.
• ClassEditor: Facilitates class type conversion.
• CustomDateEditor: Deals with customized date formatting.
• FileEditor: Manages file type conversion.
• LocaleEditor: Handles locale-related conversions.
• StringArrayPropertyEditor: Manages String array property editing.
• StringTrimmerEditor: Handles String trimming.

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What are the advantages of the spring framework? 

The Spring framework offers several advantages, including:

• Layered Architecture: Spring promotes a structured and organized layered architecture.
• POJO Programming: It facilitates Plain Old Java Object (POJO) programming, ensuring simplicity and testability.
• Dependency Injection (DI) and Inversion of Control (IoC): Spring’s DI and IoC concepts simplify JDBC interactions and enhance flexibility.
• Open-Source Framework: Spring is an open-source tool that can be employed for both commercial and non-commercial purposes.

How is Hibernate accessed using the Spring framework? 

Hibernate can be accessed through the Spring framework using the following methods:

• IOC with Callback and Hibernate Template: This involves utilizing Inversion of Control (IOC) alongside a callback mechanism and the Hibernate Template class to interact with the Hibernate ORM.

• AOP Interceptor and HibernateDaoSupport: Another approach is to employ an Aspect-Oriented Programming (AOP) interceptor along with the HibernateDaoSupport class, which extends Spring’s data access support and simplifies Hibernate integration.

What are the various Channels supported by Spring 2.0? 

 

Spring version 2.0 supports the following channels:

• Pollable Channel: Enables polling for messages.
• Subscribable Channel: Supports message subscriptions.
• Publish-Subscribe Channel: Distributes messages to multiple subscribers.
• Queue Channel: Ensures message queuing.
• Priority Channel: Manages message prioritization.
• Rendezvous Channel: Allows communication between sender and receiver.
• Direct Channel: Provides direct point-to-point communication.
• Executor Channel: Executes messages using a specified executor.
• Scoped Channel: Maintains message scope within a specified context.

 

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Why is declarative transaction management preferred in Spring? 

Declarative transaction management is favored in Spring due to its minimal impact on application code, making it an ideal and lightweight container for managing transactions. This approach simplifies the management of transactional behavior without requiring extensive modifications to the codebase.

Explain the concept of a BeanFactory.

The BeanFactory embodies the factory pattern within the Inversion of Control (IoC) paradigm, enabling a clear segregation between an application’s dependencies and configuration on one hand, and its core code on the other.

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What are the different scopes of spring bean? 

Spring beans can have different scopes, including:

• Singleton: A single instance of the bean is created and shared throughout the application context.

• Prototype: A new instance of the bean is created every time it is requested.

• Request: A new instance is created for each HTTP request in a web application.

• Session: A single bean instance is created and shared across a user’s session in a web application.

• Global Session: This scope is specific to a global session in a Portlet context, where a single instance is shared across all portlets in the same session.

What are all the ways to access Hibernate by using Spring? 

There are two primary methods to access Hibernate via Spring:

• Inversion of Control with Hibernate Template and Callback: This approach involves utilizing the Hibernate Template, which offers a simplified way to work with Hibernate sessions and transactions. Additionally, callback mechanisms can be employed to manage specific operations within these sessions.

• Extending HibernateDAOSupport and Applying AOP Interceptor: Another method involves extending the HibernateDAOSupport class provided by Spring. By doing so, you can leverage the benefits of Aspect-Oriented Programming (AOP) interception to manage cross-cutting concerns such as transaction handling and error management.

How struts application can be integrated with spring? 

Integrating a Struts application with Spring can be achieved through two approaches:

• Using ContextLoader Plugin: Configure Spring to manage beans through the ContextLoader plugin and establish their dependencies within a Spring context file.

• Explicit Retrieval of Spring Beans: Access Spring-managed beans directly by utilizing the getWebApplicationContext() method.

What is Inversion of control (IOC)? 

Inversion of Control (IoC), also known as Dependency Injection, is a design pattern that transfers the control of class instantiation from the class itself to the assembler. In typical scenarios, a class creates instances of other classes when necessary.

However, in this pattern, the responsibility of instantiation is shifted to the assembler. The assembler will create instances of necessary classes as and when required. This promotes a more flexible and modular approach to constructing software components.

Write the benefits of using IOC? 

IoC, or dependency injection, offers significant benefits for application development:

• Reduced Coding Effort: IoC minimizes the amount of code needed, streamlining application development.
• Simplified Testing: Testing becomes faster and more straightforward, thanks to the elimination of JNDI lookup and singleton usage.
• Efficient Resource Management: IoC containers handle resource management, enhancing efficiency.
• Lazy Loading: IoC supports lazy loading of services, optimizing performance.
• Eager Installation: It also allows for eager installation of services, ensuring readiness when needed.

These advantages collectively contribute to more efficient, maintainable, and well-structured software development.

What is Inner bean? What is the drawback of inner bean? 

An Inner Bean refers to a bean element that is directly enclosed within a property tag during the process of wiring beans. This encapsulation allows for a more concise configuration. However, the drawback of Inner Beans lies in their limited reusability and reprocessing capabilities. Once defined within a property tag, an Inner Bean cannot be easily reused or reconfigured, potentially limiting flexibility in certain scenarios.

What are the different types of Injection in spring? 

Spring offers three injection types:

• Setter Injection: Dependencies are injected through setter methods.
• Constructor Injection: Dependencies are provided via constructor parameters.
• Method Injection (Getter Injection): Dependencies are injected through methods.

 

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What are the benefits of the spring framework? 

The Spring framework offers the following benefits:

• Lightweight Container: Compared to J2EE containers, Spring provides a lightweight container for managing application components.

• Built-in Web MVC Framework: It includes a built-in framework for developing web applications following the Model-View-Controller architecture.

• Loosely Coupled Applications: Spring facilitates the creation of loosely coupled applications, enhancing flexibility and maintainability.

• Aspect-Oriented Programming: Spring supports aspect-oriented programming, enabling features like logging, transaction management, and security to be efficiently integrated.

• XML Configuration: Configuration is easily written and understood using XML format.

What are the types of Advice? 

Spring offers five types of Advice:

• Before Advice: Executed before the target method, allowing preparation or validation.
• After Returning Advice: Runs after successful completion of the target method, dealing with result processing.
• After Throwing Advice: Triggers when an exception occurs in the target method, handling error scenarios.
• Finally Advice: Executes regardless of method outcome, often used for resource cleanup.
• Around Advice: Encompasses the target method, granting control over its invocation and behavior.

What is called PreparedStatementCreator? 

The PreparedStatementCreator serves as a frequently utilized interface for database data insertion. Through its createPreparedStatement() method, a PreparedStatement is crafted and returned based on the supplied Connection argument, with built-in exception handling. Notably, this interface can be accompanied by another interface, SqlProvider, which features a getSql() method for furnishing SQL strings to the JdbcTemplate. It is important to note that SQLExceptions are not managed by this interface.

What is SQLProvider? 

SQLProvider serves a specific purpose through its singular method, getSql(), which is realized using implementations of PreparedStatementCreator. Its primary function revolves around aiding in debugging processes.

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