JSR-330 Standard Annotations

Starting with spring 3.0, spring begins to support annotations of the JSR-330 standard (dependency injection). These annotations and spring annotations are scanned in a way that developers only need to configure the relevant jar packages in classpath.

If a developer uses MAVEN to manage a project, javax.inject artifact is available in the Maven repository (http://repo1.maven.org/maven2/javax/inject/javax.inject/1/). Developers only need to refer to this dependency in the Pom.

<dependency>    <groupId>javax.inject</groupId>    <artifactId>javax.inject</artifactId>    <version>1</version></dependency>

Pass @InjectAnd @NamedMake Dependency Injection

In JSR-330, the @javax.inject.Inject same responsibilities as in spring @Autowired :

import javax.inject.Inject;public class SimpleMovieLister {    private MovieFinder movieFinder;    @Inject    public void setMovieFinder(MovieFinder movieFinder) {        this.movieFinder = movieFinder;    }    public void listMovies() {        this.movieFinder.findMovies(...);        ...    }}

and @Autowired consistent, developers can use @Inject dependency injection in instance variables, methods, and construction parameter levels. Also, developers can declare injections as Provider , by Provider.get() requesting those beans that are either short-scoped or deferred-initialized. For example, the following examples:

import javax.inject.Inject;import javax.inject.Provider;public class SimpleMovieLister {    private Provider<MovieFinder> movieFinder;    public void listMovies() {        this.movieFinder.get().findMovies(...);        ...    }}

If the developer wants to qualify the injected bean by name, you can use @Named annotations:

import javax.inject.Inject;import javax.inject.Named;publicclass SimpleMovieLister {    private MovieFinder movieFinder;    @Inject    publicvoidsetMovieFinder(@Named("main") MovieFinder movieFinder) {        this.movieFinder = movieFinder;    }    // ...}

@Named: Equivalent to @ComponentAnnotations

In JSR-330, the responsibilities in spring are similar to the @javax.inject.Named @Component following:

import javax.inject.Inject;import javax.inject.Named;@Named("movieListener")publicclass SimpleMovieLister {    private MovieFinder movieFinder;    @Inject    publicvoidsetMovieFinder(MovieFinder movieFinder) {        this.movieFinder = movieFinder;    }    // ...}

@ComponentOften do not need to specify the name of the use, the @Named annotations are the same:

import javax.inject.Inject;import javax.inject.Named;@Namedpublicclass SimpleMovieLister {    private MovieFinder movieFinder;    @Inject    publicvoidsetMovieFinder(MovieFinder movieFinder) {        this.movieFinder = movieFinder;    }    // ...}

@NamedYou can also use component scans when using annotations:

"org.example")public class AppConfig  {    ...}

Unlike spring's @Component components, JSR-330 Named annotations cannot be combined and use spring's component annotations if you want to customize component annotations.

Limitations of JSR-330 Standard annotations

When using JSR-330 standard annotations, it is also necessary to understand the different points of the spring annotations, as shown in the following table:

Spring	javax.inject.*	Javax.inject Restrictions
@Autowired	@Inject	@InjectAnnotations have no required attributes, but can be replaced by Java 8 Optional
@Component	@Named	The jsr_330 standard does not provide a composite model, there is only one way to identify the component
@Scope ("singleton")	@Singleton	JSR-330 The default scope is similar to spring, prototype However, why it is consistent with spring's default, beans in the JSR-330 standard are also singleton by default in spring. If you want to use a non-singleton scope, the developer should use spring @Scope annotations. java.injectan annotation is also provided @Scope , however, this annotation can only be used when creating a custom scope.
@Qualifier	@Qualifier/@Named	javax.inject.Qualifieris just a meta-annotation used to build a custom qualifier. A string qualifier (such as in spring @Qualifier ) can be used javax.inject.Named to implement the
@Value	-	Unequal price
@Required	-	Unequal price
@Lazy	-	Unequal price
Objectfactory	Provider	javax.inject.ProviderIs ObjectFactory another spring option, which get() Provider can be used in combination with spring by means of proxy. @Autowired

JSR-330 Standard Annotations