Top 20 Spring Framework Testing Interview Questions Answers for 2 to 5 Years Experienced

Testing is an important part of Software development but many people don't pay attention to it only to find bugs in the later stages of development that can be easily avoided by unit testing. When it comes to Java and Spring Boot development, we are lucky to have JUnit, Mockito, JsonPath, AssertJ, and some in-built testing facilities on Spring Framework and Spring Boot for our testing needs. Since the advent of DevOps, there is an increased focus on automation testing and that's why unit testing and integration testing has become important topics on Java Interviews and it's essential for Java developers to have in-depth knowledge about how to test a Spring framework and Spring Boot based Java application.

Difference between @Autowired and @Qualifier Annotation in Spring Framework? Example Tutorial

Hello Java programmers, the difference between @Autowired and @Qualifier annotations in Spring is a common question frequently asked in Spring on Java interviews, and if you are looking for an answer then you have come to the right place. Earlier, I have shared the best Spring courses and books, and in this article, Since most Java developers are familiar with annotations in Spring, they need to understand the difference between them and where to use them. Autowiring is a Spring Framework feature that enables you to inject the object dependency implicitly. This was added to Spring 2.5 to make an annotations-driven dependency injection that helps to "injects" objects into other objects or "dependencies." 

Difference between @RequestMapping and @GetMapping in Spring MVC? Example

Hello Java programmers, if you are wondering what is the difference between @RequestMapping and @GetMapping annotation in Spring MVC and when and how to use them then you have come to the right place. Earlier, I have shared the best Spring MVC coursesand books, and In this tutorial, we are going to discuss spring and spring boot web services. In there, most of the interviewers asked about the difference between @RequestMapping and @GetMapping annotations in spring applications. Before going to discuss the difference between these annotations, first, understand what is @RequestMapping?, How do we use the @RequestMapping?, What is a request? and types of them.

How HTTP Basic Authentication works in Spring Security?

In the last article, you have learned how to enable Http basic authentication in Spring security-based Java application, and now we'll go one step further to understand how exactly http basic authentication works in Spring security. If you remember, when you use HTTP Basic for authentication purposes, the client, like a browser or a rest client sends login credentials in the http request header. The header is aptly named "Authorization," and it contains a Base64 encoded string, which is created by concatenating username and password using a colon. For example, if the username is "johnsmith" and the password is "JOHN3214" then they will be concatenated as "johnsmith:JOHN3214" before encoded using base 64 encoding algorithms.

How to limit number of concurrent session in a Java web application using Spring Security?

If you don't know, Spring security can limit the number of sessions a user can have in a Java web application. If you are developing a web application especially a secure web application in Java JEE then you must have come up with the requirement similar to many online banking portals have like only one session per user at a time or no concurrent session per user. If the user tries to open a new session then either an alert is shown or his previous session is closed. Even though you can also implement this functionality without using spring security but with Spring security, it's just a piece of cake with coffee :). 

2 Ways to setup LDAP Active Directory Authentication in Java - Spring Security Example Tutorial

The LDAP authentication is one of the most popular authentication mechanism around the world for enterprise application and Active directory (an LDAP implementation by Microsoft for Windows) is another widely used LDAP server. In many projects, we need to authenticate against active directory using LDAP by credentials provided in the login screen. Sometimes this simple task gets tricky because of various issues faced during implementation and integration and no standard way of doing LDAP authentication in a Java web application. Even though Java provides LDAP support but in this article, I will mostly talk about spring security because of it's my preferred Java framework for authentication, authorization, and security-related stuff.

What is SecurityContext and SecurityContextHolder in Spring Security?

The SecurityContext and SecurityContextHolder are two fundamental classes of Spring Security. The SecurityContext is used to store the details of the currently authenticated user, also known as a principle. So, if you have to get the username or any other user details, you need to get this SecurityContext first. The SecurityContextHolder is a helper class, which provides access to the security context. By default, it uses a ThreadLocal object to store security context, which means that the security context is always available to methods in the same thread of execution, even if you don't pass the SecurityContext object around. Don't worry about the ThreadLocal memory leak in web application though, Spring Security takes care of cleaning ThreadLocal.

Role based Access control using Spring Security and MVC, Mapping LDAP Groups to Authorities for Authorization

Authentication and Authorization is an integral part of any Java enterprise or web application. Since most of the company uses LDAP Active directory for authentication, authorization, and Role-based access control (RBAC), it's good to know How to implement Role-based access control using Spring MVC and Spring Security. This is the second part of my articles on using Spring Security for authentication and authorization in Spring MVC based Java application. In the last part, we have learned about doing LDAP authentication against Windows active directory, and in this Spring Security tutorial, we will learn How to map LDAP groups to authorities for implementing Role-based access control or authorization.

Difference between Setter vs Constructor Injection in Spring

Spring Setter vs. Constructor Injection

Spring supports two types of dependency Injection, using a setter method, e.g. setXXX(), where XXX is a dependency or via a constructor argument. The first way of dependency injection is known as setter injection while later is known as constructor injection. Both approaches of Injecting dependency on Spring bean has there pros and cons, which we will see in this Spring framework article. The difference between Setter Injection and Constructor Injection in Spring is also a popular Spring framework interview question. 

What is Bean scope in Spring MVC framework with Example

Bean scope in Spring framework or Spring MVC is scope for a bean managed by Spring IOC container. You may know that Spring is a framework that is based on Dependency Injection and Inversion of Control and provides bean management facilities to Java application. In Spring-managed environment bean (Java Classes) are created and wired by the Spring framework. Spring allows you to define how those beans will be created and the scope of the bean is one of those details. 

Top 20 Spring Boot Interview Questions with Answers for Java Developers

Hello Java developers, there is no doubt that the Spring Boot is now the standard way to develop Java application using Spring Framework, and that's why Spring Boot Questions are increasingly becoming popular on Java interviews. In the past, I have shared many Spring MVC interview questions in this blog like the @RestController vs. @Controller, but I haven't got a chance to share any questions on Spring Boot, Spring Cloud, and Microservices. After a couple of personal requests from my readers, I thought to write about, and here comes my list of top 20 Spring Boot interview questions for Java developers.

What is the Use of DispatcherServlet in Spring MVC Framework?

If you have worked with Spring MVC then you should know what is a DispatcherServlet? It's actually the heart of Spring MVC, precisely the C of MVC design pattern or Controller. Every single web request which is supposed to be processed by Spring MVC goes through DispatcherServlet. In general, its an implementation of Front Controller Pattern which provides a single point of entry in your application. It handles all incoming requests. It is also the bridge between Java and Spring. Btw, the DispatcherServlet is like any other Servlet is declared in the web.xml with a URL pattern but the only special thing is that the URL pattern for dispatcher servlet is enough to map every single web request to DispathcherServlert.

Difference between @Component, @Service, @Controller, and @Repository in Spring

Before you learn the difference between @Component, @Service, @Controller, and @Repository annotations in the Spring framework, it's important to understand the role of @Component annotation in Spring. During the initial release of Spring, all beans are used to be declared in an XML file. For a large project, this quickly becomes a massive task, and Spring guys recognize the problem rather quickly. In later versions, they provide annotation-based dependency injection and Java-based configuration. From Spring 2.5 annotation-based dependency injection was introduced, which automatically scans and registers classes as Spring bean which is annotated using @Component annotation.

Top 20 Spring and REST Interview Questions Answers for Java/JEE Programmers

Hello guys, I have been sharing a lot of REST with Spring tutorials from last a couple of weeks and today, I am going to share some of the frequently asked Spring and REST interview questions to Java developers applying for Web developer roles. Since Spring Framework is the most popular and the standard framework for developing Java web application and RESTful Web Services, a good knowledge of Spring core and Spring MVC is expected from any senior Java developer, but if the job description mention about REST and Web Services, you also need to be aware of how to develop RESTful Web Services using Spring Framework.

Difference between @RestController and @Controller Annotation in Spring MVC and REST

The @RestController annotation in Spring MVC is nothing but a combination of @Controller and @ResponseBody annotation. It was added into Spring 4.0 to make the development of RESTful Web Services in Spring framework easier. If you are familiar with the REST web services you know that the fundamental difference between a web application and a REST API is that the response from a web application is generally view (HTML + CSS + JavaScript)  because they are intended for human viewers while REST API just returns data in form of JSON or XML because most of the REST clients are programs. This difference is also obvious in the @Controller and @RestController annotation.