Spring Boot Annotations

Spring Boot Annotations

@SpringBootApllication
we use this annotation to mark the main class


@EnableAutoConfiguration
as its name says, enables auto-configuration. it means that Spring Boot looks for auto-configuration beans


@ConditionalOnClass and @conditionalOnMissingClass
using these conditions spring will only use the marked auto-configuration bean if the class in the 
annotations argument is present/absent


@ConditionalOnBean and @ConditionalOnMissingBean
use these annotations when we want to define conditions basen on the presence or absence of a specific beans


@ConditionalOnProperty
With this annotation, we can make conditions on the values of properties


@ConditionalOnResource
We can make Spring to use a definition only when a specific resource is present


@ConditionalOnWebApplication and @ConditionalOnNotWebApplication
With these annotations, we can create conditions basen on if the current application is or isn`t web app


@ConditionalExpression
We can use this annotations in more complex situations, spring will use the marked definition when the
Spel expressions in evaluated to true


@Conditional
For even more complex conditions we can create a class eveluating the custom condition 
we tell spring to use this custom condition with @Conditional


@EnableAsync
With this annotation, we can enable asynchronous functionality in Spring. We must use it with @Configuration


@EnableScheduling
With this annotation, we can enable scheduling in the app. We also have to use it in conjunction with @Configuration


@Async
We can define methods we want to execute on a different thread, hence run them asynchronously.


@Scheduled
If we need a method to execute periodically, we can use this annotation


@Transactional
When we want to configure the transactional behavior of a method.


@Param
We can pass named parameters to our queries using @Param


@Id
Marks a field in a model class as the primary key.


@Transient
We can use this annotaion to mark a field in a model class as transient. Hence the data store engine 
wont read or write this field`s value


@CreatedBy
@LastModifiedBy
@CreatedDate
@LastModifiedDate
Whit these annotations, we can audit our model classes.Spring automatically populates the annotated fields with the 
principal who created the object.


@Query
We can provide a JPQL implementation for a repository method.


@Repository
DAO or Repository classes usually represent the database access layer in the app.


@Service
The business logic of an app usually resides within te service layer


@Controller
Is class level annotation which tells the Spring what this class serves as a controller


@Configuration
Configuration classes can contain bean definition methods