Spring Boot Interview Question

Q. What exactly is the Spring Framework?

Spring is a general-purpose development framework for Java programs but is better suited for web and application development. It allows them to use much of the Java functionality out of other libraries while adding some new features. While it is an open-source application, it can be developed in an open manner using the Creative Common platform of the Spring Framework’s integral features. The majority of the functionality can be found in a Java Enterprise program. It has several plugins and APIs that augment the Java EE platform.

We’re able to take advantage of the power of Java during the Spring phase by developing large-scale, complex, cross-platform Java applications. We also use patterns like Dependency Injection and Aspect-Oriented architecture in our software development projects.

Q. Spring vs. Spring Boot

Many people consider the Java Spring Framework to be the most useful development framework. The Spring Framework’s primary function is Dependency Injection, also known as Inversion of Control (IoC). We can build a loosely coupled application with the help of the Spring Framework. It is preferable to use this method if the application’s type or characteristics are well specified.

Spring Boot is a Spring Framework module. It enables us to build a stand-alone application with minimal or no configuration. If we want to build a simple Spring-based application or RESTful services, we can use it.

The following are the main differences between Spring and Spring Boot:

Q. What is Spring Boot, and why do you need it?

Spring Boot is a spring module that makes it easier to use the Spring framework for Java creation and build micro services. You can build Spring-based applications that you don’t have to install. Removes a large number of configurational and dependency requirements. It also includes auto dependency resolution, embedded HTTP servers, endpoints, and auto-configuration, with the spring-boot-web MVC system. You will be up and running quickly with Spring by creating your project and writing your first without complex configuration.

That is why it is so common among Java programmers. It’s relatively simple to create and understand spring applications. Furthermore, since it removes the time-consuming configuration process, you can build and deploy applications more quickly, resulting in increased performance and productivity.

Q. Describe some of the benefits of Spring Boot.

Spring Boot has many advantages:

• The Spring Framework’s primary focus is on the fundamental set of components, which have a very small size. It is simple to integrate and requires little overhead. The standard version has only 2 MB.

• Developing Spring-based applications in Java or Groovy is a breeze.

• IT saves you a lot of time and gets the job done.

• In Aspect-Oriented Java, Spring actively supports and provides. It lets business logic within the system be separate from system-wide functionality. For example, logging could be an issue across multiple applications.

• It removes the need to write a lot of boilerplate code, such as tedious annotations, configuration, and documentation.

• Most libraries from the Spring Boot ecosystem are inherently simple to use, including JDBC, Spring ORM, Spring Data, Spring Security, etc.

• It is based on “opinionated configuration” to save the developer time.

• It includes embedded HTTP servers such as Tomcat, Jetty, and others that make developing and testing web applications a breeze.

• Developing and testing Spring Boot applications from the command line is made very simple and fast using the “CLI.”

• It includes many plugins that make it simple to create and test Spring Boot applications using build tools such as Maven and Gradle.

• Several plugins allow you to work with embedded and in-memory databases with no hassle at all.

• Default initialization to automatically load a collection of default values for new application installations.

• Develops stand-alone applications with a variety of non-functional features that are popular in many project types.

Q. Describe a few important features of Spring.

Check out some of the significant characteristics:

1. Spring CLI – The purpose of Spring Boot CLI is to provide a lightweight, easy-to-use way to quickly and consistently create Spring-based web applications with less boilerplate code.
2. Starter Dependency – With the use of this mechanism, Spring Boot increases efficiency over time.
3. Auto-Configuration – if you operate on the same type of application, then the Spring Boot auto-configuration function loads default configurations. If you refrain from installing any unneeded WAR files, you’ll get rid of all the WARM files.
4. Spring Initializer – This is essentially a web application that can help you build an internal project framework. And so you don’t have to set up the project’s structural framework. You can make use of this function.
5. Spring Actuator – This helps when running spring-boot applications.
6. Logging and Security – The Spring Boot logging and security features ensure you don’t have to worry about securing each application you make.
7. Give a list of the ways an application could be configured.

Running the same application in different environments is a significant advantage of using Spring Boot. Since this uses the information, it gets from the assistance. It can be done with the help of an external configuration. Various ways to obtain the configuration properties are listed here, including environment variables, property files, command-line arguments, and YAML files. When using the @value annotation, the properties can be accessed as well. These are the places in which external configuration could be applied:

• Application Properties – By default, Spring Boot looks for properties files in the application, the class path root directory, or the properties directory to use in the application.
• Command-line properties – Command-line arguments are converted to properties by Spring Boot. Finally, it attaches the environment property to the environment to the set.
• Profile-specific properties – We load these properties from the app.properties file, unless otherwise specified. Non-specific property files can be found in the same directory, and the placeholder references an active profile.

Q. Can you illustrate what happens in the background when you “Run as Java Application” a Spring Boot application?

To launch a Spring Boot application while you are creating web applications, you can provide the spring-boot-run-server command, which will start up, and when a server is up, it automatically start, tomcat.

Q. What are the modules in the Spring framework’s Data Access/Integration layer?

The Data Access and Integration layer of the Spring framework is made up of a lot of modules:

JDBC module: A layer of abstraction that minimizes the tediousness of writing JDBC coding.

Object Relational Mapping (ORM) modules are needed to combine the database data with object data for complex models.

OXM module: An abstraction layer supports object XML mapping.

Java Messaging Service (JMS) module: message-generating and message-consuming module.

Transactions module: For POJO classes, transaction management is needed.

Q. Explain the benefits of the Spring Actuator.

Spring Actuator gives you an interactive visualization of what’s happening in your Spring Boot application. So you need to know what’s going on inside your app when you debug. And as in this situation, the Actuator has many interactive features, including bean, CPU use. There are plenty of production-ready REST endpoints given, so it’s easy to access them with the Actuator. This data is obtained using the Spring Security technique of content negotiation.

Q. What is Spring Boot dependency management, and how does it work?

The Spring Boot dependency management feature is often used to keep track of dependencies without supplying their exact version numbers.

Q. Explain what thymeleaf is and how to use it.

Your Java applications have Thymeleaf, which is a templating engine to use on the server. Since it integrates well with the Spring Framework and HTML5, it aims to serve as a neutral framework for web applications. Adding Thymeleaf code to the pom.xml file is needed. 

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring‐boot‐starter‐thymeleaf</artifactId>
</dependency>

Q. Is it possible to modify the embedded Tomcat server’s port in Spring Boot?

The property file allows us to modify the embedded tomcat server’s port. To create a port in this file, you must also specify a “server.port” and then map it to any port. Assigning it to the server.port=8081 means you must identify the server port number. One time you say the port number, the appropriate configurations will be added to the application automatically. 

Q. What are the benefits of using Spring Boot DevTools?

Spring Boot Dev Tools are a comprehensive collection of tools that help to simplify the process of creating an application. If the program runs in development, this module is disabled by default, and archive repackaging is also disabled. As a result, properties are applied to the respective development environments by the Spring Boot Developer Tools. Simply add the following dependency to the pom.xml file to include the DevTools:

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring‐boot‐devtools</artifactId>
</dependency>

Q. Describe how to use Spring Initializer to build a Spring Boot project.

Spring Initializer is a part of the Spring web tool set. You can only have project specifics and make a Spring Boot project with it. In order to build a Spring Boot project using the Spring Initializer, follow these steps:

Select the project and necessary dependencies. After you’ve given Group, Artifact, select the “Generate Project.”

When you’ve finished downloading the project, uninstall it to your system.

Next, you can use the import command on the Spring Toolbar application.

When you are preparing to import the project, ensure that the project form is Maven and that it must include the pom.xml file.

Following all the above steps, you can see that the project has successfully loaded and all dependencies have been resolved.

Q. Describe Spring Data.

It helps developers use relational and non-relational databases, as well as other data-in-as-aided resources in the cloud. This, essentially, allows data access while preserving the original data.

Q. Disabling auto-configuration in Spring Boot, what do you mean?

The program uses Auto-configuration to ensure that all appropriate settings are set automatically. If the data source is present in the classpath, the JDBC prototype would be. With Auto-configuration, you can quickly generate a Java applications.

To remove the automatic configuration, you must remove the @EnableAutoConfiguration attribute. @EnableAutoConfiguration(exclude={DataSourceAutoConfiguration.class})

To exclude auto-configuration, you must have this code:

@EnableAutoConfiguration(excludeName={Sample.class})

Aside from that, Spring Boot allows you to use the spring.autoconfigure.exclude property to exclude a list of auto-configuration classes. You can either add the attribute in one property or divide it into multiple key-value pairs with a comma.

Q. Could you provide an example of ReadOnly being valid in Transaction Management?

The following is an example of ReadOnly as TRUE in transaction management:

Consider a situation in which you could read data from a database. For example, in a customer database, such as customerID, you might want to look up information such as name and username. For that, you must set the transaction as read-only, so we will not search the entities for changes.

Q. Could you please describe how to use Spring Boot to deploy to a different server?

The steps for deploying a different server with Spring Boot are:

A WAR file can be generated from a project

Now you can upload the WAR file to one of your choice server

Note: The phase to deploy the WAR file depends on the kind of server you want to deploy it on.

Q. Can we use Spring Boot to build a non-web application?

Yes, by removing the web dependencies from the classpath and modifying the way Spring Boot generates the application context, we can build a non-web application.

Q. How do I bind an external database such as MySQL or Oracle?

You must follow these steps to link to an external database:

First, provide the MySQL Connector dependency to the pom.xml.

Follow these steps to delete H2 dependency from pom.xml .

You now, then go ahead and bind to the MySQL and your database.

Q. Describe the benefits of the YAML file over the Properties file, as well as the various methods for loading the YAML file in Spring boot.

The YAML format enables data to be stored in a hierarchical format has a distinct benefit over a properties file. So they can isolate, and repair bugs are minimized, which makes debugging a breeze for developers. Whenever you’re using the SnakeYAML lib on your classpath, you can use the SpringApplication class. As explained by the official guide to YAML in Spring Framework, the various ways to create YAML files in Spring Boot are:

• Use YamlMapFactoryBean to load YAML as a Map.

• Use YamlPropertiesFactoryBean to load YAML as Properties.

Q. How did Hibernate become the default JPA implementation with no configuration?

We automatically add the spring-boot-starter-data-jpa dependency to our pom.xml file when we use the Spring Boot Configuration. Since this classpath dependence has transitive class Hibernate dependency on Hibernate, the current Hibernate implementation is automatically assigned.

Q. At which point of a transaction, should we start the boundary?

Since the reasoning for the business transaction is already present in this layer, the transaction boundary should begin there.

Q. How do you set up Log4j to log data?

Since the configuration logger has Spring Boot logger support, you must exclude Logback and add Log4j2. The project needs to be used to complete this task.

Q. Make a distinction between WAR and embedded containers.

Q. Why do you believe Profiles are necessary?

Profiles are used to separate the various parts of an application’s configuration and make it usable in different environments. A @Profile can be used to restrict the size of any @Component or @Configuration as it is loaded. Consider the fact that you’ll be working in a variety of settings.

• Dev

• QA

• Stage

• Production

Let’s assume you want different device configurations in each of your environments. Different framework configurations for different environments can be created using profiles. As a result, Spring and Spring Boot include features that enable you to specify:

The active profile for a specific environment

The configuration of various environments for various profiles.

Q. What are the steps for using Spring Boot to add custom JS code?

The following are the steps for adding custom JS code to Spring Boot:

Now, under the resources folder, make a folder called static.

This folder is where you can place the static content.

Note: To be on the safe side, you can avoid the browser refusing the request, either disable security or look for the password in the logfile and transfer it to the application in the header.

Q. What is the simplest way to auto-configuration if a bean exists?

You must use the @ConditionalOnMissingBean annotation to tell an auto-configuration class when a bean is missing. This property has the following values:

value: The type of beans to be checked to be stored in this attribute.

name: The name of the beans to be checked is stored in this attribute.

Q. Why is it not recommended using Spring Data REST in real-world applications?

Real-world applications should avoid using Spring Data REST because the entities are exposed as RESTful Services. The two most critical considerations in designing a RESTful service are the domain model and the consumers. Both of these parameters are ignored when using the Spring Data REST. These organizations are revealed directly. When you first start to build a project using Spring Data REST, you don’t have to write lots of API code, just follow the DSLs.