Spring Boot Interview Questions And Answers- Part 2

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The essential components of Spring Boot are as follows:

• Spring Boot Starter
• Spring Boot autoconfiguration
• Spring Boot Actuator
• Spring Boot CLI

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Spring CLI represents a Command Line Interface for Spring Boot. CLI can run Groovy scripts that eliminate the need to write boilerplate code; thus, it enables them to focus on business logic. It is the fastest way to create Spring-based applications.

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The properties of a Spring Boot application can be defined into a file called application.properties. You can use Spring Initializer to create the file.

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Spring Boot support three main embedded containers:

• Jetty
• Tomcat
• Undertow
• Spring Boot uses Tomcat as an embedded container by default

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Hibernate facilitates ORM or Object-Relational Mapping. It enables users to retrieve, store, map, & update application’s data to & from Java objects & relational databases. Hibernate maps the Java data types to Structured Query Language or SQL data types, and the classes in Java are mapped to the database tables. Thus, it relieves developers from scripting data persistence SQL programs.On the other hand, a Spring Data JPA provides an abstraction over the Data Access Layer, applying JPA & ORM implementations, such as Hibernate. JPA renders the smooth implementation of JPA repositories. It aims to improve the overall implementation of the Data Access Layer to a great extent.

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The shutdown is an endpoint that helps applications to be shut down smoothly. It is not enabled by default. Thus, to enable the shutdown feature, you need to use management.endpoint.shutdown.enabled=true in the application.properties file.

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• RequestMapping:It is one of the annotations of the Spring Model View Controller. The RequestMapping annotation is mainly used for mapping web requests into some specific handler classes & handler methods. One of the major benefits of this annotation is that it can be applied to both the controller class & methods. Generally, @requestmapping is considered as a class-level annotation. One can redefine the RequestMapping with the help of the method level.
  It is advised to be specific when declaring a RequestMapping on the controller methods as it is a lengthy annotation that requires more typing than the GetMapping method. Due to its time taking nature & need for long typing code, it is often only used for framing the base path & not for other levels. Coding with the RequestMapping annotation can result in a complex & lengthy code that may become troublesome for coders as it is difficult to pick out errors from so code lines.
• GetMapping:It is also a Spring annotation used in mapping HTTP GET requests into some specific handler methods. GetMapping is not usually used in mapping the handler classes. It is an annotation that acts as a shortcut of RequestMapping. Also, the lines of code in GetMapping are comparatively less than RequestMapping. Getmapping is relatively a new annotation that was developed to overcome the drawbacks of RequestMapping annotation. It can be considered as a specialization with RequestMapping annotation that can be used to map & get requests only.

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LiveReload means a Spring Boot DevTools module that includes an embedded server named as LiveReload. It enables applications to automictically trigger a browser refresh when we make any changes in the resources. It is also called auto-refresh.

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Hot-swapping is a way to reload the changes without restarting the Jetty or Tomcat server. Eclipse and many other IDEs support the bytecode hot swapping. If you have made changes that do not affect the method signature, then it should reload without any side effects.

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Auto-configuration is a feature of Spring Boot used to configure a Spring application based on the classpath parameter’s dependencies. It helps to make easier & faster development.

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Spring Boot utilizes Apache Commons logging for all the internal loggings. It has default configurations that render support for Log4j2, Java Util Logging, & Logback. You can configure the console & file logging using these logging options.

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Cross-Origin Resource Sharing, abbreviated as CORS, is a security mechanism that restricts resource implementation in web browsers. It prevents JavaScript code from consuming or producing requests against different origins.

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Spring Boot allows developers to run the same application in different environments through external configuration. It deploys properties files, environment variables, YAML files, system properties, & command-line arguments to mention the required configuration properties. Below are some possible sources of external configuration:

• Application Properties- By default, Spring Boot searches for an application YAML file or properties file in the current directory, config directory, or classpath root to load the properties.
• Command-line properties-Spring Boot offers command-line arguments & converts them to properties. It then adds them to a set of environment properties.
• Profile-specific properties– These properties are loaded from an application-{profile}. YAML file or properties file. It resides in the same location as the non-specific property files & the{profile} placeholder refers to an active profile.

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Spring Data aims to streamline the use of cloud-based data services, relational, non-relational databases, & other data access technologies. It makes it easy to access data while retaining the underlying data.

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Both @SpringBootApplication & @EnableAutoConfiguration annotations are used to enable the auto-configuration of Spring Boot; however, they do share some differences. The @SpringBootApplication annotation performs more functions than @EnableAutoConfiguration. It is a combination of three annotations:

• @Configuration- It is used in Java-based configuration on Spring.
• @ComponentScan- This annotation enables scanning of the components you write, e.g., @Controller classes.
• @EnableAutoConfgiuration- It enables auto-configuration in the Spring Boot applications.

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To register a custom auto-configuration class with Spring Boot, you must have its fully-qualified name listed under the EnableAutoConfiguration key in the META-INF/spring.factories file.

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Swagger is a specification, open-source tool & complete framework implementation for producing visual representation or APIs of RESTful Web Services. It allows documentation to be updated at the same pace as that of the server.

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Spring Batch offers reusable functions essential in processing large volumes of records, such as tracing/logging, job restart, job processing statistics, transaction management, & resource management. It provides more advanced technical features & services that enable high-volume & performance batch jobs through partitioning & optimization techniques. To implement Spring Batch, you need to add the annotation of @EnableBatchProcessing in the configuration class file.

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FreeMarker refers to a server-side Java template engine for both standalone & web environments. These templates are written in (FTL) FreeMarker Template Language, which is a specialized & simple language. The programmers can work on the application’s code while the designers can work on its Html page design. By FreeMarker, these functions can be combined to give the final output page.

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AOP or Aspect-Oriented Programming refers to a programming pattern that enlarge modularity by allowing the separation of a cross-cutting concern different from the main business logic. One can add an additional behavior to the existing code without modification of the code.