SpringBoot

SpringBoot

• SpringBoot Application : 

• Pros & Cons : 

• SpringBoot Application creation using spring.io : 

• SpringBoot Application Annotations : 

                    @SpringBootApplication : 

                            @SpringBootConfiguration

                            @EnableAutoConfiguration

                            @ComponentScan

                        

• SpringBoot Application RestApi representation : 

• SpringBoot Application RestApi with SpringJpa with CRUD operations :

• Create

• Insert

• Update

• Delete

• SpringBoot Application RestApi with JPA Repository with Relationships : 

• One to many

• Many to one 

• Many to many

• One to one

Spring boot Interview Based Questions

Annotations : 

@SpringBootApplication : will take care of everything

@SpringBootConfiguration : will take about the configurations

@EnableAutoConfiguration : it configures the classpath beans

@ComponentScan : will scan all the classes 

ex : adding mongo dependency in the pom but beans no need to specify, enable auto configuration will take care.

SpringBoot Console Application : 

    

Diff between SpringBootConfiguration vs EnableAutoConfiguration

@Sterotype :

@Service :

@Controller :

@Componet :

@ResponseBody :

@ResponseEntity :

@Lazy :

IOC vs Dependency Injection :

    Earlier we are provind the dependency injection in xml but after spring boot comes its easy to inject the bean using @Autowired.

Diff mvc and spring boot ::

                Springboot                                            SpringMVC

    ==> embeded server                                        ==> need to configure the server
    ==> embeded db                                                ==> need to configure the db

    ==> faster development                                     ==> takes time to develop

    ==> avoid boilerplate code                                

SpringProfiling : using Profile we can instantiate the bean to the particular env.

For dev env we can instantiate the few beans for production we can instantiation using spring profiling.

Retry mechanism : 

@EnableRetry is used to retry the springboot application. It will retry the calls when exception occurs.

@Retryable(value=RuntimeException.class)

What is the starter dependency of the Spring boot module : web starter, Test starter , Data JPA starter.

How can you configure the RestTemplate in Spring not springBoot : 

        ==> ApplicationContext ctx = new AnnotationConfigApplicationContext(RestTemplate.class)

                RestTemplate rs = ctx.getBean(RestTemplate.class);

How can you secure your api in Spring not SpringBoot(SpringWebFilter)

        @EnableWebSecurity and overrride the configure(HttpSecurity http) method

When the beans will destroy in SpringBoot : 

When the beans will initialize : By Starting the springboot tomcat server or applicaiton starting time.

Bean Life Cycle :    

            ==> ContainerStarted --> Bean instantiated --> Dependcies injected --> Init() -> destroy()

    

Spring Actuator Apis : 

            ==> Health check purpose 

            ==>  /health

            ==> / beans

            ==> /caches

            ==> /configProps

            ==> /env

What is thymeleaf?

   

Spring cloud config server : 

GraphQL : Graphql is a query language to retrive the data from servers. Its a alternative to SOAP and REST and GRPC. 

The main steps of creating a GraphQL Java server are:

1. Defining a GraphQL Schema.
2. Deciding on how the actual data for a query is fetched

GraphQL offers a solution to both of these problems. It allows the client to specify exactly what data it desires, including from navigating child resources in a single request, and allows for multiple queries in a single request.
It also works in a much more RPC manner, using named queries and mutations, instead of a standard mandatory set of actions. This works to put the control where it belongs, with the API developer specifying what's possible, and the API consumer specifying what's desired.

2 Piller of GraphQL : 

1. GraphQL Schema
2. GraphQL Query Language

Email Sending Configuration

Email Configuration

Step 1 : Need Spring Email Dependency 

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

Step 2 : Required Email properties 

Properties props = new Properties ();
props.put ("mail.smtp.auth", Boolean.TRUE);
props.put ("mail.smtp.starttls.enable", Boolean.TRUE);
props.put ("mail.smtp.host", "smtp-mail.outlook.com"); // gmail : smtp-mail.gmail.com
props.put ("mail.smtp.port", "587");

Step 3 : Use below code to send email using springboot application 

try
{
   Session session = Session.getInstance(props, new javax.mail.Authenticator()
   {
      protected PasswordAuthentication getPasswordAuthentication()
      {
         return new PasswordAuthentication("user-email", "user-password");
      }
   });
   Message msg = new MimeMessage(session);
   msg.setFrom(new InternetAddress("user-email", false));

   msg.setRecipients(Message.RecipientType.CC,
         InternetAddress.parse("user-mails"));

   msg.setRecipients(Message.RecipientType.TO,
         InternetAddress.parse("user-email"));
   msg.setSubject("Email Configuration");
   msg.setSentDate(new Date());

   MimeBodyPart messageBodyPart = new MimeBodyPart();
   messageBodyPart.setContent("MESSAGE_BODY",
         MediaType.TEXT_HTML_VALUE);

   Multipart multipart = new MimeMultipart();
   multipart.addBodyPart(messageBodyPart);

   MimeBodyPart attachPart = new MimeBodyPart();
   attachPart.attachFile(file);
   multipart.addBodyPart(attachPart);
   msg.setContent(multipart);
   Transport.send(msg);
}
catch (Exception exe)
{
   log.error ("error @ Email sending {} ", exe);
}