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Using JSR 330 Standard Annotations
Spring offers support for JSR-330 standard annotations (Dependency Injection). Those annotations are scanned in the same way as the Spring annotations. To use them, you need to have the relevant jars in your classpath.
If you use Maven, the
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Dependency Injection with @Inject
and @Named
Instead of @Autowired
, you can use @jakarta.inject.Inject
as follows:
-
Java
-
Kotlin
import jakarta.inject.Inject;
public class SimpleMovieLister {
private MovieFinder movieFinder;
@Inject
public void setMovieFinder(MovieFinder movieFinder) {
this.movieFinder = movieFinder;
}
public void listMovies() {
this.movieFinder.findMovies(...);
// ...
}
}
import jakarta.inject.Inject
class SimpleMovieLister {
@Inject
lateinit var movieFinder: MovieFinder
fun listMovies() {
movieFinder.findMovies(...)
// ...
}
}
As with @Autowired
, you can use @Inject
at the field level, method level
and constructor-argument level. Furthermore, you may declare your injection point as a
Provider
, allowing for on-demand access to beans of shorter scopes or lazy access to
other beans through a Provider.get()
call. The following example offers a variant of the
preceding example:
-
Java
-
Kotlin
import jakarta.inject.Inject;
import jakarta.inject.Provider;
public class SimpleMovieLister {
private Provider<MovieFinder> movieFinder;
@Inject
public void setMovieFinder(Provider<MovieFinder> movieFinder) {
this.movieFinder = movieFinder;
}
public void listMovies() {
this.movieFinder.get().findMovies(...);
// ...
}
}
import jakarta.inject.Inject
class SimpleMovieLister {
@Inject
lateinit var movieFinder: Provider<MovieFinder>
fun listMovies() {
movieFinder.get().findMovies(...)
// ...
}
}
If you would like to use a qualified name for the dependency that should be injected,
you should use the @Named
annotation, as the following example shows:
-
Java
-
Kotlin
import jakarta.inject.Inject;
import jakarta.inject.Named;
public class SimpleMovieLister {
private MovieFinder movieFinder;
@Inject
public void setMovieFinder(@Named("main") MovieFinder movieFinder) {
this.movieFinder = movieFinder;
}
// ...
}
import jakarta.inject.Inject
import jakarta.inject.Named
class SimpleMovieLister {
private lateinit var movieFinder: MovieFinder
@Inject
fun setMovieFinder(@Named("main") movieFinder: MovieFinder) {
this.movieFinder = movieFinder
}
// ...
}
As with @Autowired
, @Inject
can also be used with java.util.Optional
or
@Nullable
. This is even more applicable here, since @Inject
does not have
a required
attribute. The following pair of examples show how to use @Inject
and
@Nullable
:
public class SimpleMovieLister {
@Inject
public void setMovieFinder(Optional<MovieFinder> movieFinder) {
// ...
}
}
-
Java
-
Kotlin
public class SimpleMovieLister {
@Inject
public void setMovieFinder(@Nullable MovieFinder movieFinder) {
// ...
}
}
class SimpleMovieLister {
@Inject
var movieFinder: MovieFinder? = null
}
@Named
and @ManagedBean
: Standard Equivalents to the @Component
Annotation
Instead of @Component
, you can use @jakarta.inject.Named
or jakarta.annotation.ManagedBean
,
as the following example shows:
-
Java
-
Kotlin
import jakarta.inject.Inject;
import jakarta.inject.Named;
@Named("movieListener") // @ManagedBean("movieListener") could be used as well
public class SimpleMovieLister {
private MovieFinder movieFinder;
@Inject
public void setMovieFinder(MovieFinder movieFinder) {
this.movieFinder = movieFinder;
}
// ...
}
import jakarta.inject.Inject
import jakarta.inject.Named
@Named("movieListener") // @ManagedBean("movieListener") could be used as well
class SimpleMovieLister {
@Inject
lateinit var movieFinder: MovieFinder
// ...
}
It is very common to use @Component
without specifying a name for the component.
@Named
can be used in a similar fashion, as the following example shows:
-
Java
-
Kotlin
import jakarta.inject.Inject;
import jakarta.inject.Named;
@Named
public class SimpleMovieLister {
private MovieFinder movieFinder;
@Inject
public void setMovieFinder(MovieFinder movieFinder) {
this.movieFinder = movieFinder;
}
// ...
}
import jakarta.inject.Inject
import jakarta.inject.Named
@Named
class SimpleMovieLister {
@Inject
lateinit var movieFinder: MovieFinder
// ...
}
When you use @Named
or @ManagedBean
, you can use component scanning in the
exact same way as when you use Spring annotations, as the following example shows:
-
Java
-
Kotlin
@Configuration
@ComponentScan(basePackages = "org.example")
public class AppConfig {
// ...
}
@Configuration
@ComponentScan(basePackages = ["org.example"])
class AppConfig {
// ...
}
In contrast to @Component , the JSR-330 @Named and the JSR-250 @ManagedBean
annotations are not composable. You should use Spring’s stereotype model for building
custom component annotations.
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Limitations of JSR-330 Standard Annotations
When you work with standard annotations, you should know that some significant features are not available, as the following table shows:
Spring | jakarta.inject.* | jakarta.inject restrictions / comments |
---|---|---|
@Autowired |
@Inject |
|
@Component |
@Named / @ManagedBean |
JSR-330 does not provide a composable model, only a way to identify named components. |
@Scope("singleton") |
@Singleton |
The JSR-330 default scope is like Spring’s |
@Qualifier |
@Qualifier / @Named |
|
@Value |
- |
no equivalent |
@Lazy |
- |
no equivalent |
ObjectFactory |
Provider |
|