CODEWITHSUNDEEP
springannotations
user705414
user705414

Reputation: 21210

For the spring autodetection, what's the difference between component and service?

I think both @Component and @Service can be used to detect bean automatically, anyone can show me the difference between those two annotations?

Upvotes: 7

Views: 2411

Answers (4)

Mayur Gupta
Mayur Gupta

Reputation: 780

here is the explanation to why we need such specialisation...

In Spring 2.0 and later, the @Repository annotation is a marker for any class that fulfills the role or stereotype (also known as Data Access Object or DAO) of a repository. Among the uses of this marker is the automatic translation of exceptions.

Spring 2.5 introduces further stereotype annotations: @Component, @Service, and @Controller. @Component is a generic stereotype for any Spring-managed component. @Repository, @Service, and @Controller are specializations of @Component for more specific use cases, for example, in the persistence, service, and presentation layers, respectively.

Therefore, you can annotate your component classes with @Component, but by annotating them with @Repository, @Service, or @Controller instead, your classes are more properly suited for processing by tools or associating with aspects. For example, these stereotype annotations make ideal targets for pointcuts.

Thus, if you are choosing between using @Component or @Service for your service layer, @Service is clearly the better choice. Similarly, as stated above, @Repository is already supported as a marker for automatic exception translation in your persistence layer.

Upvotes: 0

Aravind A
Aravind A

Reputation: 9697

check the source code

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Component
public @interface Service {

    /**
     * The value may indicate a suggestion for a logical component name,
     * to be turned into a Spring bean in case of an autodetected component.
     * @return the suggested component name, if any
     */
    String value() default "";

}

Service annotation is in turn annotated with @Component . There's nothing much in difference .

Upvotes: 0

skaffman
skaffman

Reputation: 403591

As of and up to Spring 3.1, there is no difference in the way that Spring handles them. The docs say this, but in a rather obscure way:

Spring 2.5 introduces further stereotype annotations: @Component, @Service, and @Controller. @Component is a generic stereotype for any Spring-managed component. @Repository, @Service, and @Controller are specializations of @Component for more specific use cases, for example, in the persistence, service, and presentation layers, respectively. Therefore, you can annotate your component classes with @Component, but by annotating them with @Repository, @Service, or @Controller instead, your classes are more properly suited for processing by tools or associating with aspects. For example, these stereotype annotations make ideal targets for pointcuts. It is also possible that @Repository, @Service, and @Controller may carry additional semantics in future releases of the Spring Framework. Thus, if you are choosing between using @Component or @Service for your service layer, @Service is clearly the better choice. Similarly, as stated above, @Repository is already supported as a marker for automatic exception translation in your persistence layer.

So for now, @Service will be treated by Spring exactly the same as @Component, but @Service can be considered a form of documentation.

I'm not really sure why @Service was included in Spring 2.5 at all, since it doesn't seem to have any really purpose.

Upvotes: 2

fyr
fyr

Reputation: 20869

The basic difference between both annotations is that @Service is a specialization of @Component.

See also spring documentation for @Service:

Indicates that an annotated class is a "Service" (e.g. a business service facade).

This annotation serves as a specialization of @Component, allowing for implementation classes to be autodetected through classpath scanning.

A specialization of component is also a @Repository and a @Controller

Further information can be found e.g. here.

Upvotes: 4

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