Spring @Component, @Service, @Repository and @Controller annotations

We have already seen @Autowired annotation but we have used xml configuration to configure beans and inject it to container but if you use  @Component, @Service, @Repository and @Controller annotations and enable component auto scan, spring will automatically import these bean into container and you don’t have to explicitly define them in xml file.
So basically all 4 annotations are used to register bean definition with spring’s application context.

@Component:

@Component is generic annotation for bean definition and registers with application context.

@Service :

@Service is specialised component annotation which is used to annotate classes which belongs to service layer.

@Repository :

@Repository annotation is specialised component annotation which is used to annotate classes at DAO layer. It also makes unchecked exception eligible for conversion into Spring DataAccessException.

@Controller :

@ Controller annotation is specialised component annotation which is used to annotate classes at Presentation  layer. It is widely used in Spring MVC applications.

You should not use @Component annotation unless you are sure that it does not belong to @Service, @Repository and @Controller annotation.

Enable component Scanning :

All these annotations will work only when you use context:component-scan in applicationcontext.xml. It basically scans for above 4 annotated classes and registers bean with Spring application context.

Spring annotations example :

In this example,we are going to create country object with help of controller, service and Dao classes by using above annotations.
Lets first create our bean class
Country.java


CountryController,java

CountryService.java

CountryDAO.java

applicationcontext.xml

SpringApplicationMain.java

When you run above program, you will get below output:

import_contacts

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