对于最新的稳定版本，请使用 Spring Framework 6.2.0！spring-doc.cadn.net.cn

微调基于 Annotation 的 Autowiring@Primary

因为按类型自动装配可能会导致多个候选者，所以通常需要 对选择过程的更多控制。实现此目的的一种方法是使用 Spring 的@Primary注解。@Primary指示应给定一个特定的 bean 当多个 bean 是自动连接到单值的候选者时，首选项 Dependency。如果候选者中正好存在一个主 bean，则它将成为 autowired 值。spring-doc.cadn.net.cn

考虑以下定义firstMovieCatalog作为 主要MovieCatalog:spring-doc.cadn.net.cn

@Configuration
public class MovieConfiguration {

	@Bean
	@Primary
	public MovieCatalog firstMovieCatalog() { ... }

	@Bean
	public MovieCatalog secondMovieCatalog() { ... }

	// ...
}
@Configuration
class MovieConfiguration {

	@Bean
	@Primary
	fun firstMovieCatalog(): MovieCatalog { ... }

	@Bean
	fun secondMovieCatalog(): MovieCatalog { ... }

	// ...
}

在上述配置中，以下MovieRecommender与firstMovieCatalog:spring-doc.cadn.net.cn

public class MovieRecommender {

	@Autowired
	private MovieCatalog movieCatalog;

	// ...
}
class MovieRecommender {

	@Autowired
	private lateinit var movieCatalog: MovieCatalog

	// ...
}

相应的 bean 定义如下：spring-doc.cadn.net.cn

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns:context="http://www.springframework.org/schema/context"
	xsi:schemaLocation="http://www.springframework.org/schema/beans
		https://www.springframework.org/schema/beans/spring-beans.xsd
		http://www.springframework.org/schema/context
		https://www.springframework.org/schema/context/spring-context.xsd">

	<context:annotation-config/>

	<bean class="example.SimpleMovieCatalog" primary="true">
		<!-- inject any dependencies required by this bean -->
	</bean>

	<bean class="example.SimpleMovieCatalog">
		<!-- inject any dependencies required by this bean -->
	</bean>

	<bean id="movieRecommender" class="example.MovieRecommender"/>

</beans>