因為按類型綁定可能會對于到多個合適的對象,所以在選擇上要額外處理,一種方式就是用spring注解`@Primary`,當有多個可以綁定的對象時,選擇此注解的bean, 如下,我們有`firstMovieCatalog` 作為主要的`MovieCatalog` ~~~java @Configuration public class MovieConfiguration { @Bean @Primary public MovieCatalog firstMovieCatalog() { ... } @Bean public MovieCatalog secondMovieCatalog() { ... } // ... } ~~~ 結合以上配置,下面的`MovieRecommender `會注入`firstMovieCatalog` ~~~java public class MovieRecommender { @Autowired private MovieCatalog movieCatalog; // ... } ~~~ 基于xml的配置,等同如下: ~~~xml <?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 http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://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> ~~~