此版本仍在开发中，尚不被认为是稳定的。对于最新的稳定版本，请使用 Spring Framework 6.2.10！spring-doc.cadn.net.cn

微调基于注释的自动接线@Primary或@Fallback

由于按类型自动布线可能会导致多个候选者，因此通常需要 对选择过程有更多的控制权。实现此目的的一种方法是使用 Spring 的@Primary注解。@Primary表示应该给出一个特定的 bean 当多个 bean 是自动连接到单值的候选对象时的首选项 Dependency。如果候选者中恰好存在一个主 Bean，则它将成为 autowired 值。spring-doc.cadn.net.cn

请考虑以下定义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 { ... }

	// ...
}

或者，从 6.2 开始，有一个@Fallback用于划分的注释 除要注射的常规豆子之外的任何豆子。如果只有一个常规 bean 是 left，它实际上也是主要的：spring-doc.cadn.net.cn

@Configuration
public class MovieConfiguration {

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

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

	// ...
}
@Configuration
class MovieConfiguration {

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

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

	// ...
}

对于上述配置的两种变体，以下内容MovieRecommender使用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>