Using JSR 330 standard annotations
Starting from Spring 3.0, Spring offers support for JSR-330 standard annotations (Dependency Injection).
Those annotations are scanned in the same way as the Spring annotations. You just need to have the relevant jars in your classpath.
If you are using Maven, the javax.inject artifact is available on the standard Maven repository (http://repo1.maven.org/maven2/javax/inject/javax.inject/1/). You just need to add the following dependency to your file pom.xml:
<dependency>
<groupId>javax.inject</groupId>
<artifactId>javax.inject</artifactId>
<version>1</version>
</dependency>
Dependency Injection with <interfacename>@Inject</interfacename> and <interfacename>@Named</interfacename>
Instead of @Autowired, javax.inject.Inject may be used as follows:
import javax.inject.Inject;
public class SimpleMovieLister {
private MovieFinder movieFinder;
@Inject
public void setMovieFinder(MovieFinder movieFinder) {
this.movieFinder = movieFinder;
}
// ...
}
As for @Autowired, it is possible to use @Inject at the class-level, field-level, method-level and constructor-argument level.
If you would like to use a qualified name for the dependency that should be injected, you should use the @Named annotation as follows:
import javax.inject.Inject;
import javax.inject.Named;
public class SimpleMovieLister {
private MovieFinder movieFinder;
@Inject
public void setMovieFinder(@Named("main") MovieFinder movieFinder) {
this.movieFinder = movieFinder;
}
// ...
}
<interfacename>@Named</interfacename>: a standard equivalent to the <interfacename>@Component</interfacename> annotation
Instead of @Component, javax.inject.Named may be used as follows:
import javax.inject.Inject;
import javax.inject.Named;
@Named("movieListener")
public class SimpleMovieLister {
private MovieFinder movieFinder;
@Inject
public void setMovieFinder(MovieFinder movieFinder) {
this.movieFinder = movieFinder;
}
// ...
}
It is very common to use @Component without specifying a name for the component. @Named can be used in a similar fashion:
import javax.inject.Inject;
import javax.inject.Named;
@Named
public class SimpleMovieLister {
private MovieFinder movieFinder;
@Inject
public void setMovieFinder(MovieFinder movieFinder) {
this.movieFinder = movieFinder;
}
// ...
}
When using @Named, it is possible to use component-scanning in the exact same way as when using Spring annotations:
<beans>
<context:component-scan base-package="org.example"/>
</beans>
Limitations of the standard approach
When working with standard annotations, it is important to know that some significant features are not available as shown in the table below:
Spring annotations vs standard annotations
Spring
javax.inject.*
javax.inject restrictions / comments
@Autowired
@Inject
@Inject has no 'required' attribute
@Component
@Named
@Scope("singleton")
@Singleton
jsr-330 default scope is like Spring's prototype. However, in order to keep it consistent with Spring's general defaults, a jsr-330 bean declared in the Spring container is a singleton by default. In order to use another scope than singleton, you should use Spring's @Scope annotation.
javax.inject also provides a @Scope annotation. Nevertheless, this one only aims to be used for creating your own annotations.
@Qualifier
@Named
@Value
-
no equivalent
@Required
-
no equivalent
@Lazy
-
no equivalent