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使用 JSR 330 标准注释
Spring 提供对 JSR-330 标准注释（依赖注入）的支持。那些 Comments 的扫描方式与 Spring Comments 相同。要使用它们，您需要 以将相关的 jar 放在 Classpath 中。
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如果您使用 Maven，则 |
依赖项注入@Inject和@Named
而不是@Autowired，您可以使用@jakarta.inject.Inject如下：
-
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.
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:
Table 1. Spring component model elements versus JSR-330 variants
Spring
jakarta.inject.*
jakarta.inject restrictions / comments
@Autowired
@Inject
@Inject has no 'required' attribute. Can be used with Java 8’s Optional instead.
@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 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 a scope other than singleton,
you should use Spring’s @Scope annotation. jakarta.inject also provides a
jakarta.inject.Scope annotation: however, this one is only intended to be used
for creating custom annotations.
@Qualifier
@Qualifier / @Named
jakarta.inject.Qualifier is just a meta-annotation for building custom qualifiers.
Concrete String qualifiers (like Spring’s @Qualifier with a value) can be associated
through jakarta.inject.Named.
@Value
-
no equivalent
@Lazy
-
no equivalent
ObjectFactory
Provider
jakarta.inject.Provider is a direct alternative to Spring’s ObjectFactory,
only with a shorter get() method name. It can also be used in combination with
Spring’s @Autowired or with non-annotated constructors and setter methods.