Annotations in Spring Boot

Regarding Spring Boot Annotations for Semster

Anotations

• Annotations are a form of meta data that provides data about a program

• Provides Supplemental information about a program

• Does not have a direct effect on the operation of the code

Types of Spring Boot Annotation

• Spring Core Annotation

• Spring Web Annotation

• Spring Web Annotation

• Spring Scheduling Annotation

• Spring Data Annotation

• Spring Bean Annotation

Core Annotation

• These Annotations belong to the spring core module

• They provide meta data to manage beans, dependency injection and control the application context without requiring a XML file

Core Annotation Example

• Dependency Injection Relate Annotations

  • @Autowired

  • @Qualifier

  • @Bean

  • @Primary

  • @Lazy

• Context Configuration Annotation

  • @Profile

  • @Import

  • @Import Resource

Dependency Injection related Annotations Code Example

//Field Injection

class Student{
@Autowired
Address address;}

//Constructor Injection

class Student{
@Autowired Student(){

//Setter Injection

class Student{

Address address;

@Autowired
void setAddress(Address ad){

address = ad;}

Context Configuration Annotations Code Example

@Component @Profile("developer") class Student{}

Spring Web Annotation

• Spring Web Annotations are a part of the Spring MVC Framework

• Used to build web applications and restful API

• help to map HTTP request to Java methods, data binding, and define controller behaviour

Examples for Spring Web Annotation

• @Request Mapping

• @Response Body

• @Path Variable

• @Controller

Request Mapping Code

@Request mapping (value = "url")
class Demo{

@Get Request("url continuation")
some function to be executed

• @Request Mapping is a class level annotation

• Used to map HTTP request to their respective methods

• It is a generic annotation as it can be used for any HTTP method like GET, POST, PUT, DELETE.

@Response Body

@Response Body

//Followed by similar code to before

• It can be applied on both classes and methods

• It tells the spring to return the method’s return value as the response body(ex : JSON)

@Controller

@Controller

//Followed by request mapping code

• Marks a Java class as a web controller making it responsible for handling HTTP requests

Spring Boot Annotations

• These simplify the development of restful API

• Work on top of the spring framework and focus on auto configuration

Examples for Spring Boot Annotation

• @Spring Boot Application

• @Enable Auto Configuration

Auto-Configuration Conditions

• @Conditional on Class

• @Conditional on Bean

• @Conditional on Property

• @Conditional on Resource

• @Conditional on Web Application

• @Conditional on Not Web application

• @Conditional

Example for @Spring Boot Application

@SpringBootApplication
public class MyApplication {
    public static void main(String[] args) {
        SpringApplication.run(MyApplication.class, args);
    }
}

• This annotation is used to mark the main class of a spring boot application

• It encapsulates @Configuration, @Enable Auto Configuration, @Component Scan

Spring Scheduling Annotation

• Used to run tasks at a fixed interval or according to a cron expression

• Helpful for automated tasks

Example for Scheduling Annotations

• @Enable Async

• @Enable Scheduling

• @Scheduled

• @Async

Spring Data Annotations

• Used to map Java classes with database entities

• Simplify data access when using JPA, Mongo DB or other spring modules

Spring Data Annotations Example

• Common data Annotations

  • @Id

  • @Params

  • @Created By

  • @Last Modified By

  • @Created Date

• Common Spring JPA Annotations

  • @Query

  • @Procedure

  • @Lock

• Common Mongo Annotation

  • @Query

  • @Document

  • @Field

Spring Bean Annotation

• Used to define and manage beans in a spring container

• Essential for making objects available for dependency Injection

Examples for Spring Bean Annotation

• @Component

• @Component Scan

• @Configuration