1.What is the Spring framework, and what are its key features?
Answer:“The Spring framework is an open-source Java platform that provides comprehensive infrastructure support for developing robust Java applications. Its key features include dependency injection, aspect-oriented programming, easy integration with various frameworks, and support for various application architectures.”
2.Explain the concept of dependency injection in Spring.
Answer:“Dependency injection is a design pattern used to develop loosely coupled code. In Spring, it allows the creation of objects dependent on other objects. The injector supplies the dependencies to the object (beans) instead of the object creating them. This approach makes the code more modular, easier to test, and facilitates easier management of dependencies.”
3.What are the different types of dependency injection supported by Spring?
Answer:“Spring supports three types of dependency injection: constructor injection, setter injection, and method injection. Constructor injection involves passing dependencies through a class constructor. Setter injection involves setting the dependencies through setter methods. Method injection involves injecting dependencies through specific methods.”
4.Explain the concept of Inversion of Control (IoC) in the context of the Spring framework.
Answer:“Inversion of Control in the Spring framework refers to the mechanism through which the control of object creation and lifecycle is shifted from the application code to the Spring container. It helps in creating loosely coupled and modular applications, allowing developers to focus on business logic rather than managing object lifecycles.”
5.How does Spring support aspect-oriented programming (AOP)?
Answer:“Spring AOP provides a way to enable cross-cutting concerns in application code. It allows developers to modularize cross-cutting concerns such as logging, security, and transaction management. Spring AOP uses aspects to enable the separation of concerns, and it integrates seamlessly with the Spring framework, making it easy to implement and manage.”
6.Explain the use of the Spring MVC framework and its components.
Answer:“Spring MVC is a part of the Spring framework that provides a powerful way to create Java web applications. Its components include the model, view, and controller. The model represents the business data, the view represents the presentation layer, and the controller handles the user requests, processes them, and returns the appropriate response.”
7.What is Spring Boot, and how does it differ from the Spring framework?
Answer: “Spring Boot is a part of the Spring framework that provides an opinionated way to build production-ready applications quickly. It simplifies the configuration and setup of Spring applications, making it easier to create stand-alone, production-grade Spring-based applications. Unlike the Spring framework, Spring Boot reduces the need for boilerplate code and configuration, allowing developers to focus more on writing business logic.”
8.How does Spring integrate with other Java frameworks and libraries?
Answer:Spring integrates with other Java frameworks and libraries through various mechanisms, making it a versatile and widely adopted framework for building enterprise applications.
9.Explain the role of the Spring MVC framework in web development.
Answer:“Spring MVC is a module within the Spring framework that supports the development of web applications. It provides a powerful Model-View-Controller architecture, allowing developers to create flexible and loosely coupled web applications. The model represents the data, the view represents the presentation layer, and the controller processes the user’s requests.”
10.How does Spring support transaction management?
Answer:“Spring provides support for declarative transaction management through AOP. It simplifies the implementation of transaction management by allowing developers to define transactional boundaries using annotations or XML configurations. Spring handles the underlying transaction management details, making it easier to manage database transactions in the application.”
11.Explain Dependency Injection (DI) in the context of the Spring framework?
Answer:“Dependency Injection is a design pattern used to develop loosely coupled code. In Spring, it allows the creation of objects dependent on other objects. The injector supplies the dependencies to the object (beans) instead of the object creating them. This approach makes the code more modular, easier to test, and facilitates easier management of dependencies.”
12.What are the different ways to configure the Spring container?
Answer:The Spring container can be configured in several ways, providing flexibility to developers based on their preferences and project requirements.XML-based configuration: In this approach, the Spring container is configured using XML files. The XML configuration defines the beans, their dependencies, and the relationships between them.
13.What is inversion of control (IoC), and how is it implemented in the Spring framework?
Answer:Inversion of Control (IoC) is a design principle in software engineering that refers to the process of externalizing the construction and management of objects. In traditional programming, the application itself is responsible for creating objects and managing their lifecycle. In contrast, with IoC, the control over object creation and management is inverted and delegated to a container or framework.
14.Explain the use of the Spring Bean life cycle.
Answer:The Spring Bean life cycle refers to the various stages that a Spring bean goes through, from its instantiation to its destruction. Understanding the Spring Bean life cycle is crucial for managing and customizing bean initialization, configuration, and destruction. The life cycle consists of the following phases:
Instantiation: The Spring container creates an instance of the bean using the bean’s class and configuration metadata. This marks the beginning of the bean’s life cycle.
Populating Properties: After the bean is instantiated, the container injects the dependencies and properties into the bean using either constructor injection or setter injection.
15.Explain the use of Spring Security and its main features?
Answer:Spring Security is a powerful and highly customizable security framework that provides comprehensive security services for Java-based enterprise applications. It enables developers to secure their applications at various levels, including HTTP requests, method invocations, and domain object instances.
16.Explain the role of the DispatcherServlet in Spring MVC?
Answer:The DispatcherServlet plays a pivotal role in the Spring MVC (Model-View-Controller) framework. It acts as the front controller for managing and dispatching HTTP requests to the appropriate handlers within the Spring MVC application. Its primary responsibilities include:
Request Handling: The DispatcherServlet is responsible for intercepting and handling incoming HTTP requests from clients. It acts as the entry point for all requests, centralizing the request-handling process for the entire application.
Request Routing: Based on the configuration defined in the Spring application context, the DispatcherServlet routes the incoming requests to the corresponding controller that is capable of processing the request
17.What are the different components of the Spring MVC framework?
Answer:The Spring MVC (Model-View-Controller) framework is a part of the broader Spring framework, designed to support the development of flexible and robust web applications in Java. It consists of several key components that work together to handle web requests, process business logic, and generate the appropriate responses.
18.How does Spring provide support for RESTful web services?
Answer:Spring provides robust support for building RESTful web services through its dedicated module, Spring Web MVC. Several key features and components facilitate the development of RESTful services within the Spring framework:
Controller Annotations: Spring provides annotations such as @RestController, @RequestMapping, and @PathVariable that enable developers to create RESTful controllers with ease. These annotations help define the request mappings and handle dynamic path variables within the URI.
19.What is Spring Data, and how does it simplify data access in Spring applications?
Answer:Spring Data is a part of the larger Spring Framework that aims to simplify the development of data access layers in Java applications. It provides a unified and easy-to-use data access abstraction for relational and non-relational databases, as well as other data sources.
20.Explain the use of @RequestMapping and @PathVariable annotations in Spring MVC?
Answer:In Spring MVC, the @RequestMapping and @PathVariable annotations play key roles in mapping HTTP requests to specific handler methods within a controller. They enable developers to define the URL patterns and extract dynamic values from the request URL.
@Controller
@RequestMapping("/products")
public class ProductController {
@RequestMapping(value = "/{id}",
method = RequestMethod.GET)
public String getProduct(@PathVariable("id")
long id, Model model) {
// Method logic to retrieve
and display the product with the given ID
return "productView";
}
}
21.List the features of the Spring Framework.
Answer:The Spring Framework, a widely used open-source application framework for Java, offers a rich set of features that make it a popular choice for developing enterprise-level applications.
- Inversion of Control (IoC):This feature allows the Spring container to manage the creation and lifecycle of application objects, reducing the need for hard-coded dependencies and promoting loosely coupled code.
- Aspect-oriented Programming (AOP):Spring supports AOP, enabling developers to modularize cross-cutting concerns such as logging, security, and transactions, making the code cleaner and more maintainable.
22.Explain the benefits of using the Spring Framework.
Answer:Using the Spring Framework offers numerous benefits that contribute to the development of robust, scalable, and maintainable applications. Some of the key advantages of using the Spring Framework include:
- Inversion of Control (IoC):Spring’s IoC container manages the creation and lifecycle of objects, reducing the need for manual management of object dependencies. This leads to more modular, testable, and maintainable code.
- Modular Design:Spring’s modular design promotes the use of loosely coupled and reusable components, making it easier to build and maintain complex applications.
23.What are the different modules in the Spring Framework?
Answer:
The Spring Framework is organized into several modules, each catering to specific aspects of application development and providing different functionalities. These modules are designed to be used independently or in combination to address various requirements in enterprise application development.
24.Differentiate between inversion of control and dependency injection.
Answer:
Inversion of Control (IoC):
- Inversion of Control is a broader concept that refers to a design principle in which the control of object creation and lifecycle is transferred from the application to a container or framework.
- It essentially means that the flow of control in an application is inverted: instead of the application controlling the instantiation and management of objects, this control is delegated to a container or framework.
Dependency Injection (DI):
- Dependency Injection is a specific implementation of the Inversion of Control principle, where the dependencies of an object are provided externally rather than created within the object itself.
- The primary purpose of DI is to facilitate loose coupling between classes by delegating the responsibility of creating and managing dependencies to a separate entity.
25.Explain the concept of aspect-oriented programming (AOP) in Spring.
Answer:Aspect-Oriented Programming (AOP) is a programming paradigm that enables developers to separate cross-cutting concerns from the main business logic of an application. Cross-cutting concerns are functionalities that affect multiple parts of an application and are not related to the core business logic. Examples of cross-cutting concerns include logging, security, and transaction management.
26.What is the role of the BeanFactory in the Spring Framework?
Answer:The BeanFactory is one of the central components of the Spring Framework and plays a crucial role in managing the instantiation, configuration, and assembly of beans in a Spring application. It serves as the fundamental interface for providing configuration information to the Spring IoC container.
27.Explain the ApplicationContext in Spring.
Answer:
Bean Management: The ApplicationContext manages the lifecycle of beans within a Spring application, handling their creation, initialization, and destruction based on the configuration provided in the application context.
Dependency Injection (DI): Similar to the BeanFactory, the ApplicationContext facilitates dependency injection, allowing the injection of dependencies into beans at runtime, ensuring loose coupling and better maintainability.
28.What is the purpose of the Spring container?
Answer:The primary purpose of the Spring container is to manage the lifecycle of objects (beans) in a Spring application. It serves as the core of the Spring Framework’s Inversion of Control (IoC) container, providing essential functionalities that enable the creation, configuration, and assembly of application objects.
29.Explain the concept of Spring configuration metadata.
Answer:In the context of the Spring Framework, configuration metadata refers to the information provided to the Spring container that defines how beans should be created, configured, and managed within an application. This metadata plays a crucial role in instructing the Spring container on how to instantiate, configure, and assemble the objects in the application context.
30.What are the types of dependency injection in Spring?
Answer:
- Constructor Injection:In this approach, dependencies are provided to the dependent class through the class constructor
- Setter Injection:Setter injection involves the use of setter methods to inject dependencies into the dependent class.
- Field Injection: Field injection involves the direct injection of dependencies into the class fields using annotations such as @Autowired.
31.Explain constructor injection and setter injection in Spring.
Answer:
Constructor Injection:Constructor injection involves injecting dependencies into a class through its constructor. The required dependencies are provided as parameters to the constructor when the bean is instantiated. Here is an example:
public class MyClass {
private final Dependency dependency;
public MyClass(Dependency dependency) {
this.dependency = dependency;
}
}
public class MyClass {
private Dependency dependency;
public void setDependency(Dependency dependency) {
this.dependency = dependency;
}
}
Answer:Autowiring is a feature in the Spring Framework that automatically injects the dependencies of a bean into another bean without requiring explicit configuration. It simplifies the process of wiring beans together and reduces the need for manual configuration, making the development process more efficient.
- No Autowiring:his is the default mode in which autowiring is disabled, and dependencies must be explicitly configured using the
or tags in the XML configuration or through the @Autowired annotation in the case of annotation-based configuration. - By Name:Autowiring by name matches beans based on their names. If a bean has a dependency with a specific name, the Spring container looks for another bean with the same name to inject.
33.When would you use constructor injection over setter injection?
Answer:Constructor injection and setter injection are both methods for achieving dependency injection in the Spring Framework, each with its own advantages and use cases. The decision to use constructor injection or setter injection depends on the specific requirements and design considerations of the application.
34.Explain the @Component annotation in Spring.
AnswerIn the Spring Framework, the @Component annotation is used to denote that a class is a component or a bean that should be automatically detected and registered as a Spring bean during the component scanning process. It is a fundamental annotation that is part of the stereotype annotations provided by Spring for configuring and managing beans.
35.Explain the @Qualifier annotation in Spring.
Answer:In the Spring Framework, the @Qualifier annotation is used to resolve ambiguities when multiple beans of the same type are present in the application context. When used in conjunction with the @Autowired annotation, it helps to specify which bean should be injected.
@Component
@Qualifier("myBean")
public class MyBeanImplementation
implements MyBeanInterface {
// Class implementation
}
@Component
public class MyComponent {
@Autowired
@Qualifier("myBean")
private MyBeanInterface myBean;
// Other code
}
Answer:In the Spring Framework, the @Value annotation is used to inject values from properties files, environment variables, or any other external sources directly into Spring beans. It allows for the externalization of configuration properties, making the configuration more flexible and dynamic.
- Value Injection:The @Value annotation can be used to inject literal values, expressions, or property placeholders into Spring beans.
- External Configuration: The @Value annotation allows developers to externalize configuration properties outside of the codebase, making it possible to change the configuration without modifying the source code.
37.Explain the @Service annotation in Spring.
Answer:In the Spring Framework, the @Service annotation is used to indicate that a class is a service component in the business layer. It is a specialization of the @Component annotation and serves to provide additional clarity and semantic value to the role of the annotated class within the application.
- Role Clarification:The @Service annotation is used to mark a class as a service component, which typically encapsulates the business logic and acts as an intermediary between the controller and the data access layers.
- Automatic Bean Registration: Just like the @Component annotation, the @Service annotation enables automatic detection and registration of the annotated class as a Spring bean during the component scanning process.
38.What is the role of the @RestController annotation in Spring?
Answer:In the Spring Framework, the @RestController annotation is used to create RESTful web services. It combines the @Controller and @ResponseBody annotations to simplify the creation of web services that directly return data in the HTTP response body.
39.Describe the @RequestMapping annotation in Spring MVC.
Answer:In Spring MVC, the @RequestMapping annotation is used to map web requests to specific handler methods within a controller. It is a versatile annotation that can be used at the class level or the method level to define the URL mapping for incoming HTTP requests.
- URL Mapping:The @RequestMapping annotation is used to map a specific HTTP request to a handler method within a controller.
- HTTP Methods:The @RequestMapping annotation supports various HTTP methods such as GET, POST, PUT, DELETE, and more.
40.What is a Spring Bean?
Answer:In the Spring Framework, a bean is an object that is instantiated, assembled, and managed by the Spring IoC container. It is a fundamental component within the Spring ecosystem, representing the various components of an application that are managed by the Spring container. Beans are the building blocks of a Spring application and can represent any Java object, from simple POJOs (Plain Old Java Objects) to more complex business logic components.
41.Explain the different scopes of a Spring Bean.
Answer:In the Spring Framework, the scope of a bean defines its lifecycle and the way it is managed within the Spring IoC container. Spring provides several built-in bean scopes, each serving a specific purpose and suitable for different use cases
- Singleton:This is the default scope for a Spring bean. A singleton bean is created once, and the same instance is returned for subsequent requests.
- Prototype: In this scope, a new instance of the bean is created every time it is requested from the container.
42.What is the default scope of a Spring Bean?
Answer:The default scope of a Spring bean is the singleton scope. When a bean is declared in the Spring configuration without specifying a scope explicitly, it is by default considered to be a singleton bean. In this scope, a single instance of the bean is created, and the same instance is returned for every request for that bean within the application context. The singleton scope is suitable for stateless beans and components that can be safely shared across the application.
43.How would you create a Spring Bean using XML configuration?
AnswerTo create a Spring bean using XML configuration, you would typically define the bean within the Spring configuration file (often named applicationContext.xml or any other name ending with .xml). Here is an example of creating a simple bean using XML configuration:
<beans xmlns="http://www.springframework
.org/schema/beans"
xmlns:xsi="http://www.w3
.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework
.org/schema/beans
http://www.springframework
.org/schema/beans/spring-beans.xsd">
<bean id="myBean" class="com.example.MyBean">
<!-- You can define
properties and their values here -->
<!-- Example: -->
<!-- <property name="propertyName"
value="propertyValue" /> -->
</bean>
</beans>
Answer:In Spring, you can create beans using Java-based configuration by using the @Configuration annotation along with the @Bean annotation to define and configure the beans. Here’s an example:
import org.springframework.context.annotation.Bean;
import org.springframework.context
.annotation.Configuration;
@Configuration
public class AppConfig {
@Bean
public MyBean myBean() {
return new MyBean();
}
}
45.Explain the concept of aspect-oriented programming (AOP) in Spring.
Answer:Aspect-oriented programming (AOP) is a programming paradigm that enables modularization of cross-cutting concerns in software. In the context of the Spring Framework, AOP provides a powerful mechanism for separating cross-cutting concerns from the core business logic of an application. A cross-cutting concern is a functionality or requirement that cuts across multiple modules or components of an application, such as logging, security, transaction management, and caching.
45.What is a pointcut in AOP?
Answer:In Aspect-Oriented Programming (AOP), a pointcut is an expression that determines the specific join points in a program’s execution flow where advice (code implementing cross-cutting concerns) should be applied. Join points represent points in the application where the execution of the program can be intercepted, such as method executions, field access, or exception handling.
46.Explain the concepts of advice and joinpoint in AOP.
Answer:In Aspect-Oriented Programming (AOP), “advice” and “joinpoint” are fundamental concepts that form the basis of how cross-cutting concerns are applied to the core application logic. These concepts are essential in understanding how aspects are implemented and executed within the AOP framework.
- Joinpoint: A joinpoint represents a specific point in the application’s execution where an aspect can be applied.
- Advice: Advice is the actual implementation of the cross-cutting concern, which is applied at a particular joinpoint in the application’s execution.
47.What are the different types of advice in Spring AOP?
Answer:In Spring AOP, there are several types of advice that can be applied to the joinpoints in a program’s execution. Each type of advice corresponds to a specific point in the execution flow of the target objects, allowing developers to intercept and modify the behavior of the application as needed.
48.Explain the difference between AOP and OOP.
Answer:
AOP
- Aspect-oriented programming deals with cross-cutting concerns that affect multiple parts of the application, such as logging, auditing, and error handling.
- Modularity in AOP is achieved through the use of aspects, which encapsulate cross-cutting concerns and can be applied to multiple parts of the application without modifying the core logic.
- AOP helps reduce code duplication by providing a way to modularize and manage cross-cutting concerns separately from the core business logic.
OOP
- Object-oriented programming primarily deals with the implementation of business logic and encapsulating data and behavior within objects.
- Modularity in OOP is achieved through the use of classes and interfaces to encapsulate related data and behavior.
- Without proper design, OOP can lead to code duplication when implementing common functionalities in multiple classes.
49.What is Spring MVC?
Answer:Spring MVC (Model-View-Controller) is a popular web framework built on top of the Spring framework, which provides a powerful way to build dynamic and robust web applications. It follows the MVC design pattern, separating the application into three main components: the model, the view, and the controller.
- Powerful request mapping capabilities to map URLs to controller methods.
- Support for data binding and form handling.
- Flexible and customizable view resolution to support different types of views, such as JSP, Thymeleaf, and others.
50.Explain the role of the DispatcherServlet in Spring MVC.
Answer:In Spring MVC, the DispatcherServlet plays a central role as the front controller that receives and processes incoming HTTP requests for a web application. It acts as the entry point for all requests and serves as a traffic cop, directing requests to the appropriate handlers for processing.
- Request Handling:The DispatcherServlet is responsible for receiving all incoming requests and routing them to the appropriate handlers based on the URL mappings configured in the application.
- Centralized Control: It acts as a central hub for managing the entire request-response lifecycle, coordinating the processing of requests, and managing the flow of control throughout the application.
51.What is the purpose of the @Controller annotation in Spring MVC?
Answer:In Spring MVC, the @Controller annotation is used to mark a class as a controller component within the MVC architecture. It indicates that the annotated class serves as a specialized type of Spring component responsible for handling and processing incoming HTTP requests. Here’s an explanation of the purpose of the @Controller annotation:
- Request Handling: The @Controller annotation is used to identify a class as a request-handling component within the Spring MVC framework.
- URL Mapping: Controllers annotated with @Controller are capable of mapping specific HTTP requests to corresponding handler methods within the class.
52.Explain the concept of a ModelAndView in Spring MVC.
Answer:In Spring MVC, a ModelAndView is a class that combines both the model and the view components and is used to carry data from a controller to a view for rendering. It represents a data structure that contains the model data and the logical view name to be resolved by the view resolver. Here’s an explanation of the concept of a ModelAndView in Spring MVC:
- Model Data: The ModelAndView object holds the model data, which is essentially a data structure containing the information that will be rendered by the view.
- Logical View Name: The ModelAndView object also holds the logical view name, which is the identifier used by the view resolver to determine the actual view that will be rendered to the client.
53.What is the role of the ViewResolver in Spring MVC?
Answer:In Spring MVC, the ViewResolver is a component that resolves the logical view names returned by the controller to the actual view templates that will be rendered and sent back to the client. It plays a crucial role in the view resolution process, allowing developers to define how the logical view names are mapped to the physical view templates.
54.Explain the purpose of the @ModelAttribute annotation.
Answer:In Spring MVC, the @ModelAttribute annotation is used to bind method parameters to a model attribute, making the data available to the view. It is typically used within a controller method to add one or more attributes to the model before returning a view.
- Data Binding: The @ModelAttribute annotation is used to bind a method parameter to a model attribute, allowing data to be transferred from the client to the server and then added to the model.
- Model Population: It facilitates the population of the model with attribute values, which can be accessed by the view for rendering.
55.What is Spring Data?
Answer:Spring Data is a part of the Spring Framework that aims to simplify the development of applications that interact with different types of data stores, including relational databases, NoSQL databases, and other data sources. It provides a unified and consistent way to work with various data access technologies, reducing the amount of boilerplate code typically required for data access operations. Spring Data encompasses a set of projects that offer different features and capabilities for working with data.
56.Explain the purpose of the JpaRepository interface in Spring Data.
Answer:The JpaRepository interface in Spring Data is a subinterface of the CrudRepository interface, providing additional JPA-specific methods for working with data persistence in a relational database using the Java Persistence API (JPA). It offers a set of convenient methods for performing CRUD (Create, Read, Update, Delete) operations and querying the database without the need for writing custom boilerplate code.
- CRUD Operations: The JpaRepository interface provides methods for performing CRUD operations, such as saving, updating, deleting, and querying entities in the underlying database.
- Query Generation: It offers support for query methods that automatically generate database queries based on method names.
57.What is Spring WebFlux?
Answer:Spring WebFlux is the new module introduced in Spring 5. Spring WebFlux is the first step towards the reactive programming model in the spring framework.
Spring WebFlux is the alternative to the Spring MVC module. Spring WebFlux is used to create a fully asynchronous and non-blocking application built on the event-loop execution model.
58.How do we implement DI in Spring Framework?
Answer:We can use Spring XML based as well as Annotation-based configuration to implement DI in spring applications. For better understanding, please read Spring Dependency Injection example where you can learn both the ways with JUnit test case. The post also contains a sample project zip file, that you can download and play around to learn more.
59. Name some of the important Spring Modules?
Answer:Some of the important Spring Framework modules are:
- Spring Context – for dependency injection.
- Spring AOP – for aspect-oriented programming.
- Spring DAO – for database operations using DAO pattern
- Spring JDBC – for JDBC and DataSource support.
- Spring ORM – for ORM tools support such as Hibernate
- Spring Web Module – for creating web applications.
- Spring MVC – Model-View-Controller implementation for creating web applications, web services, etc.
60.What is the importance of Spring bean configuration file?
Answer:We use the Spring Bean configuration file to define all the beans that will be initialized by Spring Context. When we create the instance of Spring ApplicationContext, it reads the spring bean XML file and initializes all of them. Once the context is initialized, we can use it to get different bean instances
61.How to get ServletContext and ServletConfig object in a Spring Bean?
Answer:There are two ways to get Container specific objects in the spring bean.
- Implementing Spring *Aware interfaces, for these ServletContextAware and ServletConfigAware interfaces, for a complete example of these aware interfaces, please read Spring Aware Interfaces.
- Using @Autowired annotation with bean variable of type ServletContext and ServletConfig. They will work only in servlet container-specific environments only.
62. Does Spring Bean provide thread safety?
Answer:The default scope of Spring bean is singleton, so there will be only one instance per context. That means that all the having a class level variable that any thread can update will lead to inconsistent data. Hence in default mode spring beans are not thread-safe.
However, we can change spring bean scope to request, prototype or session to achieve thread-safety at the cost of performance. It’s a design decision and based on the project requirements
63.What is a MultipartResolver and when it’s used?
AnswerMultipartResolver interface is used for uploading files – CommonsMultipartResolver and StandardServletMultipartResolver are two implementations provided by spring framework for file uploading. By default there are no multipart resolvers configured but to use them for uploading files, all we need to define a bean named “multipartResolver” with type as MultipartResolver in spring bean configurations.
Once configured, any multipart request will be resolved by the configured MultipartResolver and pass on a wrapped HttpServletRequest.
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64.What are the minimum configurations needed to create a Spring MVC application?
Answer:For creating a simple Spring MVC application, we would need to do the following tasks.
- Add spring-context and spring-webmvc dependencies in the project.
- Configure DispatcherServlet in the web.xml file to handle requests through the spring container.
- Spring bean configuration file to define beans, if using annotations then it has to be configured here. Also, we need to configure the view resolver for view pages.
- Controller class with request mappings defined to handle the client requests.
65.How would you relate Spring MVC Framework to MVC architecture?
Answer:As the name suggests Spring MVC is built on top of Model-View-Controller architecture. DispatcherServlet is the Front Controller in the Spring MVC application that takes care of all the incoming requests and delegates them to different controller handler methods.
The model can be any Java Bean in the Spring Framework, just like any other MVC framework Spring provides automatic binding of form data to java beans. We can set model beans as attributes to be used in the view pages.
View Pages can be JSP, static HTML, etc. and view resolvers are responsible for finding the correct view page. Once the view page is identified, control is given back to the DispatcherServlet controller. DispatcherServlet is responsible for rendering the view and returning the final response to the client.
66. How to upload files in the Spring MVC Application?
Answer:Spring provides built-in support for uploading files through MultipartResolver interface implementations. It’s very easy to use and requires only configuration changes to get it working. We would need to write controller handler method to handle the incoming file and process it. For a complete example, please refer Spring File Upload Example.
67.How to validate form data in Spring Web MVC Framework?
AnswerSpring supports JSR-303 annotation-based validations as well as provides a Validator interface that we can implement to create our own custom validator. For using JSR-303 based validation, we need to annotate bean variables with the required validations.
For custom validator implementation, we need to configure it in the controller class. For a complete example, please read Spring MVC Form Validation Example.
68.What is Spring MVC Interceptor and how to use it?
Answer:Spring MVC Interceptors are like Servlet Filters and allow us to intercept client requests and process them. We can intercept client requests at three places – preHandle, postHandle, and afterCompletion.
We can create a spring interceptor by implementing the HandlerInterceptor interface or by extending the abstract class HandlerInterceptorAdapter.
We need to configure interceptors in the spring bean configuration file.
69. What is the Spring JdbcTemplate class and how to use it?br>
AnswerSpring Framework provides excellent integration with JDBC API and provides JdbcTemplate utility class that we can use to avoid bolier-plate code from our database operations logic such as Opening/Closing Connection, ResultSet, PreparedStatement etc.
70. How to use Tomcat JNDI DataSource in Spring Web Application?
AnswerFor using servlet container configured JNDI DataSource, we need to configure it in the spring bean configuration file and then inject it to spring beans as dependencies. Then we can use it with JdbcTemplate to perform database operations.
<beans:bean id="dbDataSource" class="org
.springframework.jndi.JndiObjectFactoryBean">
<beans:property name="jndiName"
value="java:comp/env/jdbc/MyLocalDB"/>
</beans:bean>
Answer:Spring framework provides transaction management support through Declarative Transaction Management as well as programmatic transaction management. Declarative transaction management is most widely used because it’s easy to use and works in most of the cases.
We use annotate a method with @Transactional annotation for Declarative transaction management. We need to configure the transaction manager for the DataSource in the spring bean configuration file.
72.What is Spring DAO?
Answer:Spring DAO support is provided to work with data access technologies like JDBC, Hibernate in a consistent and easy way. For example we have JdbcDaoSupport, HibernateDaoSupport, JdoDaoSupport and JpaDaoSupport for respective technologies.
73.What is the front controller of Spring MVC?
Answer:The front controller is a DispatcherServlet class present in org.springframework.web.servlet package. It dispatches the request to the appropriate controller and manages the flow of the application. It is required to specify the DispatcherServlet class in the web.xml file.
74.What does an additional configuration file contain in Spring MVC application?
Answer:The Spring MVC application contains an additional configuration file that contains the properties information. This file can be created either in the form of an xml file or properties file. In this file, we generally define the base-package and view resolver where DispatcherServlet searches for the controller classes and view components path. However, it can also contain various other configuration properties.
75.What is Spring Cloud, and what are its key components?
Answer:Spring Cloud is a framework within the Spring ecosystem that provides tools and libraries to help developers build distributed systems and microservices-based applications. It aims to simplify the development of cloud-native applications by providing a set of features and capabilities for building, deploying, and managing distributed systems and services. Spring Cloud integrates seamlessly with the Spring ecosystem, offering various components and modules that facilitate the development of resilient, scalable, and fault-tolerant applications
76.What are classes for spring JDBC API?
Answer:
- JdbcTemplate
- SimpleJdbcTemplate
- NamedParameterJdbcTemplate
- SimpleJdbcInsert
- SimpleJdbcCall
77.Explain the purpose of the @EnableDiscoveryClient annotation in Spring Cloud.
Answer:The @EnableDiscoveryClient annotation in Spring Cloud is used to enable service discovery capabilities in a microservices-based architecture. It is typically applied to the main application class to indicate that the application should participate in service discovery. When used in conjunction with a service registry, such as Eureka or Consul, the @EnableDiscoveryClient annotation allows the application to register itself with the registry and discover other services that are registered within the same environment
78.How do you implement a distributed tracing system using Spring Cloud Sleuth?
Answer:o implement a distributed tracing system using Spring Cloud Sleuth, you need to set up the necessary configurations and dependencies in your Spring Boot application. Spring Cloud Sleuth integrates with various distributed tracing systems, such as Zipkin, Jaeger, and others, to provide visibility into the interactions and dependencies between different microservices.
79.What is the purpose of the Netflix Eureka server in Spring Cloud?
Answer:The Netflix Eureka server, when integrated with Spring Cloud, serves as a service registry that facilitates the registration and discovery of microservices within a distributed system. It provides a centralized location where microservices can register themselves, making it easier for other services to locate and communicate with them. The Eureka server plays a crucial role in enabling service discovery and load balancing in a microservices architecture
80.Explain the concept of testing in Spring.
Answer:In Spring, testing plays a crucial role in ensuring the reliability and quality of applications. Spring provides a comprehensive suite of tools and frameworks that facilitate the testing of various components, including unit tests, integration tests, and end-to-end tests. These testing capabilities help developers verify the functionality, performance, and behavior of Spring-based applications.
81.What is the purpose of the @RunWith annotation in Spring testing?
Answer:The @RunWith annotation is not a part of the Spring testing framework but is commonly used in conjunction with other testing frameworks, such as JUnit, to customize the behavior of the test runner. In the context of Spring testing, the @RunWith annotation is used to specify the test runner that should be used to execute the tests. It allows developers to integrate custom test runners or third-party test runners with the Spring testing framework. By specifying the appropriate test runner using the @RunWith annotation, developers can configure and customize the test execution environment to meet specific testing requirements.
82.Explain the use of the @MockBean annotation in Spring testing.
Answer:The @MockBean annotation is a part of the Spring Boot test framework and is used for creating and injecting mock objects into the Spring application context during testing. It is commonly used to replace the real beans with mock implementations, allowing developers to isolate the components under test and simulate the behavior of dependencies. The @MockBean annotation simplifies the process of creating mock objects and stubs for testing purposes, enabling developers to focus on testing the specific behavior of components without relying on the actual implementations of dependencies.
83.What is the difference between @Mock and @MockBean in Spring testing?
Answer:
@Mock:
- The @Mock annotation is part of the Mockito framework, which is a popular mocking framework for Java. It is typically used in standalone JUnit tests or tests that do not involve the Spring application context.
- When used with Mockito, the @Mock annotation creates a mock object of a specified class or interface, allowing developers to define the behavior of the mock and verify interactions with the mock.
- The @MockBean annotation is specific to the Spring Boot test framework and is used for creating and injecting mock objects into the Spring application context during integration testing.
- When used with Spring Boot, the @MockBean annotation creates a mock instance of a specified bean or component, allowing developers to replace the real bean with a mock implementation in the Spring application context.
84.What is the purpose of the @Transactional annotation in Spring?
Answer:The @Transactional annotation in Spring is used to manage the transactional behavior of methods or classes. It is typically applied to methods or classes that perform data access operations or modify data in a database. When a method or class is annotated with @Transactional, Spring ensures that the operations within the annotated scope are executed within a transactional context, providing features such as atomicity, consistency, isolation, and durability (ACID properties). Here’s the purpose of the @Transactional annotation in Spring:
85.Explain the concepts of advice and joinpoint in AOP.
Answer:
Joinpoint:
- A joinpoint represents a specific point in the execution of a program, such as a method invocation, a field access, or an exception being thrown. It is a point in the control flow of the program where an aspect can be applied to introduce additional behavior.
- Joinpoints are defined by specific criteria or conditions that determine when an aspect should be executed. These criteria can include method calls, field access, object instantiation, and exception handling, among others.
- Advice represents the additional behavior that is applied at a particular joinpoint. It defines the actions or functionality that should be executed at the specified joinpoint in the program’s execution flow.
- There are different types of advice that can be applied at various joinpoints, including before, after, around, after-returning, and after-throwing advice.
Answer:In Spring AOP, there are several types of advice that can be applied to joinpoints in the execution of a program. Each type of advice defines a specific aspect behavior that is executed at a particular joinpoint. The different types of advice in Spring AOP include:
- Before advice:
- After returning advice:
- After throwing advice:
- After (finally) advice:
- Around advice:
87. What is the BeanFactory – BeanFactory implementation example?
Answer:A BeanFactory is an implementation of the factory pattern that applies Inversion of Control to separate the application’s configuration and dependencies from the actual application code. The most commonly used BeanFactory implementation is the XmlBeanFactory class.
88.XMLBeanFactory?
AnswerThe most useful one is org.springframework.beans.factory.xml.XmlBeanFactory, which loads its beans based on the definitions contained in an XML file. This container reads the configuration metadata from an XML file and uses it to create a fully configured system or application.
89. Explain the AOP module?
Answer:The AOP module is used for developing aspects for our Spring-enabled application. Much of the support has been provided by the AOP Alliance in order to ensure the interoperability between Spring and other AOP frameworks. This module also introduces metadata programming to Spring.
90. Explain the object/relational mapping integration module?
Answer:Spring also supports using an object/relational mapping (ORM) tool over straight JDBC by providing the ORM module. Spring provides support to tie into several popular ORM frameworks, including Hibernate, JDO, and iBATIS SQL Maps. Spring’s transaction management supports each of these ORM frameworks as well as JDBC.
91.Explain the web module?
Answer:The Spring web module is built on the application context module, providing a context that is appropriate for web-based applications. This module also contains support for several web-oriented tasks such as transparently handling multipart requests for file uploads and programmatic binding of request parameters to your business objects. It also contains integration support with Jakarta Struts.
92.Spring configuration file?
Answer:The Spring configuration file is an XML file. This file contains the class information and describes how these classes are configured and introduced to each other.
93.What is the difference between Bean Factory and ApplicationContext?
Answer:Application contexts provide a means for resolving text messages, a generic way to load file resources (such as images), they can publish events to beans that are registered as listeners. In addition, operations on the container or beans in the container, which have to be handled in a programmatic fashion with a bean factory, can be handled declaratively in an application context. The application context implements MessageSource, an interface used to obtain localized messages, with the actual implementation being pluggable.
94.What does a Spring application look like?
Answer:
- An interface that defines the functions.
- The implementation that contains properties, its setter and getter methods, functions, etc.
- Spring AOP
- The Spring configuration XML file.
- A client program that uses the function
95.Which DI would you suggest Constructor-based or setter-based DI?
Answer:You can use both Constructor-based and Setter-based Dependency Injection. The best solution is to use constructor arguments for mandatory dependencies and setters for optional dependencies.
96.How do you provide configuration metadata to the Spring Container?
Answer:There are three important methods to provide configuration metadata to the Spring Container:
- XML-based configuration file.
- Annotation-based configuration
- Java-based configuration
97.What are inner beans in Spring?
Answer:When a bean is only used as a property of another bean it can be declared as an inner bean. Spring’s XML-based configuration metadata provides the use of elements inside the or elements of a bean definition, in order to define the so-called inner bean. Inner beans are always anonymous and they are always scoped as prototypes.
98.What is bean auto wiring?
Answer:The Spring container is able to autowire relationships between collaborating beans. This means that it is possible to automatically let Spring resolve collaborators (other beans) for a bean by inspecting the contents of the BeanFactorywithout using and elements.
99.Can you inject null and empty string values in Spring?
AnswerYes, you can.
100.What is an Annotation-based container configuration?
Answer:An alternative to XML setups is provided by an annotation-based configuration that relies on the bytecode metadata for wiring up components instead of angle-bracket declarations. Instead of using XML to describe a bean wiring, the developer moves the configuration into the component class itself by using annotations on the relevant class, method, or field declaration.
101.Which ViewResolver class is widely used?
Answer:The org.springframework.web.servlet.view.InternalResourceViewResolver class is widely used.
102.What does the ViewResolver class?
Answer:The View Resolver class resolves the view component to be invoked for the request. It defines prefix and suffix properties to resolve the view component.
103.What does @RequestMapping annotation?
Answer:The @RequestMapping annotation maps the request with the method. It is applied on the method.
104.What does @Controller annotation?
Answer:The @Controller annotation marks the class as controller class. It is applied on the class.
105.What is the front controller class of Spring MVC?
Answer:The DispatcherServlet class works as the front controller in Spring MVC.
106.How strings are represented in Java?
Answer:In some other languages, strings are represented as array of characters. But in Java, strings are represented as objects of java.lang.String class.
107.How do you create string objects in Java?
Answer:
There are two ways to create string objects in Java.
1) Using String Literals
String s1 = “ABC”;
String s2 = “123”;
2) Using new Operator
String s1 = new String(“ABC”);
String s2 = new String(“123”);
108.How string objects are stored in the memory?
Answer:Whenever you create string objects using string literals, those objects will be stored in string constant pool and whenever you create string objects using new operator, such objects will be stored in normal heap memory.
109.How to reverse a string in Java?
Answer:Any technical interview is not complete without a question on recursive concept. This question is one of them. You have to write a Java program to reverse a given string using recursive method.
110.How to check whether one string is a rotation of another in Java?
Answer:Concatenate the first string with itself and then check if the second string is a substring of the concatenated string.
111.Annotation for Hibernate exceptions to be translated into Spring’s DataAccessException for consistent exception handling?
Answer:@Repository
112. What is Bean in Spring?
Answer: In Spring, the objects that form the backbone of your application and that are managed by the Spring IoC container are called beans.
113. How to use <ref> in Spring framework?
Answer: <ref> is used with string values.
114. How does spring achieve DI or IOC?
Answer: Service locator pattern
115.What are stereo type annotations in Spring?
Answer: Annotations used for marking a class as a configuration component in Spring.
116.How to find duplicate characters in a string in Java?
Answer: Use a hashmap to store the count of each character and identify duplicates.
117.How to count occurrences of each character in a string in Java?
Answer:Iterate through the string and use a hashmap to count occurrences of each character.
118.How to check whether one string is a rotation of another in Java?
Answer:Concatenate the first string with itself and then check if the second string is a substring of the concatenated string.
119.How to reverse each word of a string in Java?
Answer: Use the String.split() method to split the string into an array of words and then reverse each word.
120.How do you find longest substring without repeating characters in a string?
Answer: Use a sliding window approach with a hash set.
121. percentage of uppercase, lowercase, digits and special characters in a string?
Answer:Calculate the total count of characters and perform arithmetic operations to find the percentage for each type.
122.How do you find longest substring without repeating characters in a string?
Answer: Use a sliding window approach with a hash set.
123.Finding The First Repeated And Non-Repeated Character In A String.Finding The First Repeated And Non-Repeated Character In A String?
Answer: Use a hashmap to store the count of each character.
124.How to remove all vowels from a string in Java?
Answer:Use the String.replaceAll() method with a regular expression.
125.Most repetitive character in a string ?
Answer: Use a hashmap to store the count of each character and then find the one with the highest count.
126.How does Spring help manage cross-cutting concerns in an application?
Answer: Using Aspect-Oriented Programming (AOP)
127.Which Spring module is specifically designed to address cross-cutting concerns?
Answer: Spring AOP
128.What is the primary purpose of using AOP in the context of the Spring Framework?
Answer: To modularize cross-cutting concerns
129. Which of the following is true regarding the implementation of AOP in Spring?
Answer: AOP enables the separation of cross-cutting concerns from the main business logic.
130. What is an “Advice” in the context of Spring AOP?
Answer: It represents the cross-cutting concern logic.
131.String to Integer and Integer to String Conversion program?
Answer: Integer.parseInt(str) is used to convert the String to an integer, and String.valueOf(num) is used to convert the integer back to a String.
132.In Spring, which annotation is used to configure a bean to be automatically detected and configured as a part of the Spring application context?
Answer: @ComponentScan
133.What is the purpose of the @Qualifier annotation in Spring?
Answer: It is used to resolve autowiring conflicts when multiple beans of the same type are present.
134.In the context of Spring Security, what is the purpose of the UserDetails interface?
Answer: It represents the user information required by the authentication provider.
135.Which annotation is used in Spring to define a bean?
Answer: @Bean
136. What is auto-wiring in Spring?
Answer: A mechanism that allows you to inject dependencies into objects automatically.
137.Which annotation is used to enable auto-wiring in Spring?
Answer: @Autowired
138.What happens when multiple beans of the same type are present in the Spring application context and auto-wiring is used without further configuration?
Answer: Spring will throw an ambiguity exception and request more specific configuration.
139.Which auto-wiring mode in Spring does not allow null values to be passed in?
Answer: constructor
140.In Spring, if no matching bean is found during auto-wiring, what will happen?
Answer: Spring will create a new instance of the required bean automatically.
141.What is the purpose of Dependency Injection in software development?
Answer: To facilitate unit testing
142.Which of the following statements best describes the concept of Inversion of Control (IoC) as it relates to Dependency Injection?
Answer: It is a process where the control of managing object creation is transferred to an external entity.
143.In Dependency Injection, which component is responsible for providing the dependent objects to a class?
Answer: Injector
144.Which of the following frameworks is commonly used for Dependency Injection in Java?
Answer: Spring
145.What are the benefits of Dependency Injection?
Answer: Increased code reusability
146.What is Spring Security primarily used for?
Answer: Authentication and Authorization
147.Which of the following is not a feature of Spring Security?
Answer: ORM (Object-Relational Mapping)
148.Which module in Spring Security is used to implement authentication and authorization for a web application?
Answer: spring-boot-starter-security
149.Which of the following authentication mechanisms is not supported by Spring Security?
Answer: FTP (File Transfer Protocol)
150.What is the default authentication provider in Spring Security?
Answer: DaoAuthenticationProvider
