Using JSR 330 Standard Annotations (Using JSR 330 Standard Annotations) _ Spring Framework6.1.13中文文档(官方文档中文翻译)|Spring 教程 —

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.spring-doc.cn

If you use Maven, the jakarta.inject artifact is available in the standard Maven repository ( https://repo.maven.apache.org/maven2/jakarta/inject/jakarta.inject-api/2.0.0/). You can add the following dependency to your file pom.xml:spring-doc.cn

<dependency>
	<groupId>jakarta.inject</groupId>
	<artifactId>jakarta.inject-api</artifactId>
	<version>2.0.0</version>
</dependency>

<dependency>
	<groupId>jakarta.inject</groupId>
	<artifactId>jakarta.inject-api</artifactId>
	<version>2.0.0</version>
</dependency>

Dependency Injection with `@Inject` and `@Named`

Instead of @Autowired, you can use @jakarta.inject.Inject as follows:spring-doc.cn

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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:spring-doc.cn

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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:spring-doc.cn

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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:spring-doc.cn

public class SimpleMovieLister {

	@Inject
	public void setMovieFinder(Optional<MovieFinder> movieFinder) {
		// ...
	}
}

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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:spring-doc.cn

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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:spring-doc.cn

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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:spring-doc.cn

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@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:spring-doc.cn

Table 1. Spring component model elements versus JSR-330 variants
Spring	jakarta.inject.*	jakarta.inject restrictions / comments
@Autowiredspring-doc.cn	@Injectspring-doc.cn	`@Inject` has no 'required' attribute. Can be used with Java 8’s `Optional` instead.spring-doc.cn
@Componentspring-doc.cn	@Named / @ManagedBeanspring-doc.cn	JSR-330 does not provide a composable model, only a way to identify named components.spring-doc.cn
@Scope("singleton")spring-doc.cn	@Singletonspring-doc.cn	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.spring-doc.cn
@Qualifierspring-doc.cn	@Qualifier / @Namedspring-doc.cn	`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`.spring-doc.cn
@Valuespring-doc.cn	-spring-doc.cn	no equivalentspring-doc.cn
@Lazyspring-doc.cn	-spring-doc.cn	no equivalentspring-doc.cn
ObjectFactoryspring-doc.cn	Providerspring-doc.cn	`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.spring-doc.cn

Table 1. Spring component model elements versus JSR-330 variants
Spring	jakarta.inject.*	jakarta.inject restrictions / comments
@Autowiredspring-doc.cn	@Injectspring-doc.cn	`@Inject` has no 'required' attribute. Can be used with Java 8’s `Optional` instead.spring-doc.cn
@Componentspring-doc.cn	@Named / @ManagedBeanspring-doc.cn	JSR-330 does not provide a composable model, only a way to identify named components.spring-doc.cn
@Scope("singleton")spring-doc.cn	@Singletonspring-doc.cn	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.spring-doc.cn
@Qualifierspring-doc.cn	@Qualifier / @Namedspring-doc.cn	`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`.spring-doc.cn
@Valuespring-doc.cn	-spring-doc.cn	no equivalentspring-doc.cn
@Lazyspring-doc.cn	-spring-doc.cn	no equivalentspring-doc.cn
ObjectFactoryspring-doc.cn	Providerspring-doc.cn	`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.spring-doc.cn

Dependency Injection with @Inject and @Named

@Named and @ManagedBean: Standard Equivalents to the @Component Annotation

Limitations of JSR-330 Standard Annotations

Dependency Injection with `@Inject` and `@Named`

`@Named` and `@ManagedBean`: Standard Equivalents to the `@Component` Annotation