Spring Boot interview questions (rpm)

Spring Boot is the best Java micro-services framework. We suggest that you can become an expert in a Spring Boot.

Issue a Spring Boot, Spring MVC and Spring What is the difference?

SpringFrame

The most important feature is SpringFramework dependency injection. Dependency injection is not all SpringModules IOC inversion of control.

When we properly use DI or the IOC, we can develop loosely coupled applications. Loosely coupled application unit testing can be easily performed.

SpringMVC

Spring MVC provides a separate way to develop Web applications. By using a few simple concepts like DispatcherServelet, MoudlAndView ViewResolver and so on, the development of Web applications will become very simple.

SpringBoot

Spring and SpringMVC problem is that you need to configure a number of parameters.

<bean
 class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="prefix">
        <value>/WEB-INF/views/</value>
    </property>
    <property name="suffix">
        <value>.jsp</value>
    </property>
  </bean>

  <mvc:resources mapping="/webjars/**" location="/webjars/"/>

Spring Boot entry by automatically configure and start a project to solve the problem. In order to quickly build application-ready products, Spring Boot provides some non-functional characteristics.

Second problem What is auto configuration?

Spring and SpringMVC problem is that you need to configure a number of parameters.

<bean
 class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="prefix">
        <value>/WEB-INF/views/</value>
    </property>
    <property name="suffix">
        <value>.jsp</value>
    </property>
  </bean>

  <mvc:resources mapping="/webjars/**" location="/webjars/"/>

Can we bring more intelligence? When a MVC JAR added to the application, we can automatically configure some beans?

See Spring (available on the CLASSPATH frame) configuration of existing applications. On this basis, Spring Boot Configuration provides the basic framework and the application required. This is automatically configured.

Question three What is Spring Boot Stater?

Initiator is a convenient descriptor is not dependent, it can be placed in their own procedures. You can get the related art Spring and you need to stop, by way of example without relying on code search descriptors and paste the copied load.

For example, if you want to use Sping and JPA access the database , only need your project consists of spring-boot-starter-data- jpa dependencies, you can be perfect.

Question four Can you give an example to explain the contents of more Staters?

Let us consider an example of a Stater -Spring Boot Stater Web.

If you want to develop an application or a web application is open REST services. Spring Boot Start Web is preferred. Let's create a Spring Boot Start Web project quickly using Spring Initializr.

Spring Boot Start Web dependencies

<dependency>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-web</artifactId>
</dependency>

The following screenshot is added to our application of different dependencies

Dependencies can be divided into

Spring - core，beans，context，aop

Web MVC - （Spring MVC）

Jackson - for JSON Binding

Validation - Hibernate,Validation API

Enbedded Servlet Container - Tomcat

Logging - logback,slf4j

Any classic Web applications will use all of these dependencies. Spring Boot Starter Web prepackaged these dependencies.

As a developer, I do not need to worry about these dependencies and their compatible version.

Five questions Spring Boot which also offers other Starter Project Options?

Spring Boot also offers other items comprises a launcher, typically including dependencies for developing specific types of applications.

spring-boot-starter-web-services - SOAP Web Services

spring-boot-starter-web - Web applications and RESTful

spring-boot-starter-test - unit and integration test

spring-boot-starter-jdbc - traditional JDBC

spring-boot-starter-hateoas - added functionality for service HATEOAS

spring-boot-starter-security - SpringSecurity use for authentication and authorization

spring-boot-starter-data-JPA - 带有 Hibeernate 的 Spring Data JPA

spring-boot-starter-data-rest - simply use the Spring Data REST REST service announcement

Question six Spring is how to quickly create product-ready applications?

Spring Boot committed to rapid product-ready applications. For this purpose, it provides a non-functional characteristics such as cache, logging, monitoring, and embedded servers out of the box.

spring-boot-starter-actuator - such as monitoring and tracking the use of some of the advanced features of the application

spring-boot-starter-undertow, spring-boot-starter-jetty, spring-boot-starter-tomcat - Choose your specific Embedded Servlet Container

spring-boot-starter-logging - logging using logback

spring-boot-starter-cache - the cache is enabled support for the Spring Framework

What are the minimum Java version ### Spring2 and Spring5 need is?

Spring Boot 2.0 requires Java8 or newer. Java6 Java7 and is no longer supported.

Method 1: Close Security verification

application.properties

management.security.enabled:FALSE

Method two: the search for the password in the log and delivered to the request headers

Question thirteen What is Spring Date?

From: //projects.spring.io/spring- data /

Spring Data's mission is to ensure that the premise of the special nature of the underlying data store, providing a familiar data access, consistency, Spring-based programming model. This makes the use of data access technology, relational databases and non-relational databases, map-reduce framework and cloud-based data services become very easy.

To make it simpler, Spring Data Abstractions provides an interface from the underlying data source limitation.

Here an example to

interface TodoRepository extends CrudRepository<Todo, Long> {

You can define a simple library to insert, update, delete, and retrieve agency matters without the need to write a lot of code.

Problem fourteen What is Spring Data REST?

Spring Data TEST can be used to publish HATEOAS RESTful resources on Spring database.

Here is an example of the use of JPA

@RepositoryRestResource(collectionResourceRel = "todos", path = "todos")
public interface TodoRepository
        extends PagingAndSortingRepository<Todo, Long> {

You do not need to write too much code, we can publish RESTful API on Spring database.

Here are some examples of display on the server TEST

POST

URL:http：//localhost：8080/todos
Use Header:Content-Type:Type:application/json
Request Content

code show as below

{
  "user": "Jill",
  "desc": "Learn Hibernate",
  "done": false
}

Response content

{
  "user": "Jill",
  "desc": "Learn Hibernate",
  "done": false,
  "_links": {
"self": {
  "href": "http://localhost:8080/todos/1"
},
"todo": {
  "href": "http://localhost:8080/todos/1"
}
  }
}

Href response contains the newly created resource.

Question fifteen path = "users", collectionResourceRel = "users" How to use with Spring Data Rest?

@RepositoryRestResource(collectionResourceRel = "users", path = "users")

public interface UserRestRepository extends
PagingAndSortingRepository<User, Long>

path- this resource to be exported path segment.
collectionResourceRel- rel values used to generate a link to a collection of resources. Used when generating HATEOAS link.

Question sixteen when Spring Boot application runs as a Java application, what happens backstage?

If you use the Eclipse IDE, Eclipse maven plug-in ensures changed dependency or class files are added - will be compiled and ready in the target file! After that, you and other Java applications same.

When you start the java application, spring boot automatic configuration file will magically enabled.

When Spring Boot application detects that you're developing a web application when it starts tomcat.

The 17- Can we jetty tomcat instead of the spring-boot-starter-web with?

Remove the existing dependency in spring-boot-starter-web, and these added to it below.

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
    <exclusions>
        <exclusion>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
        </exclusion>
    </exclusions>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-jetty</artifactId>
</dependency>

Eighteen questions on how to use Spring Boot generate a WAR file?

Recommended reading:

https://spring.io/guides/gs/convert-jar-to-war/

Here are spring documentation directly link address:

https://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/#build-tool-plugins-maven-packaging

Nineteen question of how to use Spring Boot deployed to different servers?

You need to do the following two steps:

Generate a war file in a project.
Deploy it to your favorite server (websphere or Weblogic or Tomcat and so on).

Step One: Getting Started This should help:
https://spring.io/guides/gs/convert-jar-to-war/

Step two: depending on your server.

The twenty RequestMapping and differences GetMapping Where at?

RequestMapping class having attributes, and can be requested method GET, POST, PUT, or have other comments.
GetMapping is a special case of GET request method. It is just an extension of ResquestMapping purpose is to improve clarity.

The twenty-first why we do not recommend using Spring Data Rest in practical applications?

We believe that the Spring Data Rest is suitable for rapid prototyping! In large applications need to use caution.

You can put your data entities as RESTful services directly released by Spring Data REST.

When you design a RESTful server, best practices suggest that you should take into account the interface of two important things:

Your model range.
your customer.

By With Spring Data REST, you do not need to consider these two aspects, just as the issuing entity TEST service.

This is why we recommend using Spring Data Rest in rapid prototyping above, or as a method of solving the initial project. For a complete evolution of the project, this is not a good note.

Twenty-two problem in Spring Initializer, how to change the package name of a project?

The good news is that you can customize it. Click on the link "Go to the full version." You can configure the package name you want to modify!

Twenty-three problem can configure a complete list of properties application.propertierde can be found where?

Here is the complete guide:

https://docs.spring.io/spring-boot/docs/current/reference/html/common-application-properties.html

Problem twenty-four What are the differences JPA and Hibernate have?

in short

JPA is a specification or interface
Hibernate is an implementation of JPA

When we use the JPA, we use javax.persistence package annotations and interfaces without using hibernate import packages.

We recommend using the JPA annotations, oh because we do not have to bind it to Hibernate as the implementation. Later (I know - less than one percent chance), we can use another JPA implementation.

Problem twenty-five business boundaries Where should one start?

We recommend the service layer management obligations. Commercial business logic in the business layer or service layer, at the same time, you want to perform management operations also in this layer.

Problem twenty-six use Spring Boot initiate a connection to the JPA H2-memory database applications which require a dependency?

In Spring Boot project when you make sure the following items are dependent on the class path inside, you can load H2 console.

web launcher
h2
jpa data Launcher

Other dependencies in the following:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>

<dependency>
    <groupId>com.h2database</groupId>
    <artifactId>h2</artifactId>
    <scope>runtime</scope>
</dependency>

Some caveats:

An internal data memory exists only during application execution. This is an effective way to learn the framework.
This is not the way the world is really the application you want.
In the question "how to connect an external database?", We explain how to connect a database of your choice.

Twenty-seven question of how not to choose Hibernate as the default JPA implementation by any configuration?

Because Spring Boot is automatically configured.

Here is our dependency added

<dependency>
           <groupId>org.springframework.boot</groupId>
           <artifactId>spring-boot-starter-data-jpa</artifactId>
      </dependency>

spring-boot-stater-data-jpa for Hibernate and JPA transitional dependent.

When Spring Boot detected classpath Hibernate, it will be automatically configured as the default JPA implementation.

Problem twenty-eight where specified database connection information? How does it know to automatically connect to the H2?

This is the Spring Boot automatically configured magic.

From: https: //docs.spring.io/spring-boot/docs/current/reference/html/using-boot-auto-configuration.html

Spring Boot auto-configuration attempt to automatically configure you have added Spring-based application jar dependencies. For example, if there is HSQLDBis your class path, and database connection manually configure the bean has not, then we can automatically configure a memory database.

Step - adding dependency mysql connector to pom.xml

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
</dependency>

The second step - removing H2 from the pom.xml dependency

Or at least use it as the test range.

<!--
<dependency>
    <groupId>com.h2database</groupId>
    <artifactId>h2</artifactId>
<scope>test</scope>
</dependency>
-->

The third step - installing your MySQL database

More to look at here -https: //github.com/in28minutes/jpa-with-hibernate#installing-and-setting-up-mysql

Step Four - Configure your MySQL database connection

Configuration application.properties

spring.jpa.hibernate.ddl-auto=none
spring.datasource.url=jdbc:mysql://localhost:3306/todo_example
spring.datasource.username=todouser
spring.datasource.password=YOUR_PASSWORD

Step 5 - Restart, you're ready!

It's that simple!

Questions on the default H2 database name Spring Boot configuration is the above? Why is the default database name is testdb?

In application.properties which lists all of the default values

https://docs.spring.io/spring-boot/docs/current/reference/html/common-application-properties.html

Locate the following attributes

spring.datasource.name=testdb # Name of the datasource.

If you use an H2 internal memory database, which it identifies Spring Boot H2 to install the name of your database.

Thirty-one problem if H2 is not in the class path which will appear above situation?

We will report the following error

Cannot determine embedded database driver class for database type NONE

H2 added to the pom.xml, then restart your server

<dependency>
    <groupId>com.h2database</groupId>
    <artifactId>h2</artifactId>
<scope>runtime</scope>
</dependency>

Problem thirty-two Can you give an example to ReadOnly as a transaction management?

When you read the content from the database, things you want other users described or described in read-only mode, so that no change in the entity to check again in Hebernate. This is very efficient.

Question thirty-three What is the best way to publish Spring Boot application user custom configuration is?

@Value problem is that you can assign values to configure your application. Better operation is to take centralized approach.
You can use @ConfigurationProperties define a configuration components.

@Component
@ConfigurationProperties("basic")
public class BasicConfiguration {
    private boolean value;
    private String message;
    private int number;

You can configure the parameters in application.properties.

basic.value: true
basic.message: Dynamic Message
basic.number: 100

Question thirty-four What is the demand profile?

Developing enterprise applications are complex, you need a mixed environment:

Dev
QA
Stage
Production

In each environment, you want a different application configuration.

Profile helps you configure the different applications in different environments.

Spring and Spring Boot provides functions that you can develop.

Different configuration files, configuring different environment is what?
Environmental set of activities to develop a profile.

Spring Boot configure the application will be selected according to the active profile specific environment settings.

Question thirty-five how to use the configuration file to configure specific configuration environment through Spring Boot?

Profiles do not critical environmental design.

In the following example, we will use two configuration files

dev
prod

The default application configuration in application.properties in. Let us look at the following example:

application.properties

basic.value= true
basic.message= Dynamic Message
basic.number= 100

We want to dev file application.properties custom attributes. We need to create a file named application-dev.properties, and we want to rewrite the custom attributes.

application-dev.properties

basic.message: Dynamic Message in DEV

Once you have configured the specific configuration files, you need to set a profile of activity in the environment.

There are several ways to do this:

Use Dspring.profiles.active = prod VM parameter in
Use spring.profiles.active = prod in the application.properties

Source: http://www.3xmq.com/article/1522809264295

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