[英]Spring: Injecting list of all concrete classes implementing an interface
I have an @Service
class which contains a List
of other @Service
classes.我有一个@Service
class ,其中包含其他@Service
类的List
。 That List
basically contains all the services which implements UniformEventsResearchApi
.该List
基本上包含所有implements UniformEventsResearchApi
的服务。
Being a rookie with Spring, I'm not sure how I can get Spring to allow me to follow the Open-Closed Principle and thus having that list automagically injected with all of the concrete implementations.作为 Spring 的新手,我不确定如何让 Spring 允许我遵循开闭原则,从而使该列表自动注入所有具体实现。
Here is an incomplete UML class diagram:这是一个不完整的 UML class 图:
And here is some "code":这是一些“代码”:
@Service
public class EventsResearchService {
// todo: this should be Injected automatically
private List<UniformEventsResearchApi> eventsResearchApis = Arrays.asList(new EventbriteApi());
// Already tried, but without success:
//
// @Autowired
// private List<UniformEventsResearchApi> eventsResearchApis2;
//
// @Autowired
// @Qualifier("EventsResearchApi")
// public void setXList(List<UniformEventsResearchApi> apis) {
// this.eventsResearchApis2 = apis;
// }
}
@Service
@Qualifier("EventsResearchApi")
public interface UniformEventsResearchApi { /* ... */ }
public abstract class EventsResearchApi implements UniformEventsResearchApi { /* ... */ }
/** Any class like this one which extends EventsResearchApi should be automatically injected in the List */
public class EventbriteApi extends EventsResearchApi { /* ... */ }
This is an easy task for spring actually:实际上,这对 spring 来说是一项简单的任务:
You can auto wire a list of beans just like a regular bean In this case spring will indeed find all the beans that implement the interface and inject:您可以像普通 bean 一样自动连接 bean 列表。在这种情况下,spring 确实会找到所有实现接口并注入的 bean:
public interface SomeInterface {
}
@Component
public class SomeImpl1 implements SomeInterface {}
@Component
public class SomeImpl2 implements SomeInterface {}
@Service
public сlass SampleBean {
@Autowired
private List<SomeInterface> beans;
}
One note, there should be at least one implementation of beans available, Otherwise Spring won't let you such an injection.需要注意的是,至少应该有一个可用的 bean 实现,否则 Spring 不会让你进行这样的注入。 If you know that such a situation is possible you can inject Optional<List<SomeInterface>>
如果您知道这种情况是可能的,您可以注入Optional<List<SomeInterface>>
With field injection it looks rather ugly, but you can use constructor injection (which is better anyway) or consider using “java configuration”:使用字段注入它看起来相当丑陋,但您可以使用构造函数注入(无论如何更好)或考虑使用“java配置”:
@Service
public class SampleBean {
private final List<SomeInterface> beans;
// I haven’t checked this with compiler, should work
@Autowired // optional, if you have a single constructor, you can omit it
public SampleBean(Optional<List<SomeInterface>> beans) {
this.beans = beans.orElse(Collections.emptyList());
}
}
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