java JavaConfig 中的 Spring Bean 别名
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Spring Bean Alias in JavaConfig
提问by dtrunk
I have a @Serviceannotated class which provides core functionality which I can use in all my projects:
我有一个带@Service注释的类，它提供了我可以在所有项目中使用的核心功能：
@Service
public class MyService {}
and another one which extends it to implement project specific stuff:
另一个扩展它以实现项目特定的东西：
@Service
public class ExtendedMyService extends MyService {}
Now I would like to configure a bean alias to be able to use @Qualifier("MyServiceAlias")when autowiring it using a property:
现在我想配置一个 bean 别名，以便@Qualifier("MyServiceAlias")在使用属性自动装配它时能够使用：
# MyService qualifier (default: myService)
myService.qualifier=extendedMyService
In XML it would look like:
在 XML 中，它看起来像：
<alias name="${myService.qualifier}" alias="MyServiceAlias" />
It is also discussed here, but I need to do it w/o XML, JavaConfig only. Is it possible and how to realize?
这里也讨论了它，但我只需要在没有 XML、JavaConfig 的情况下进行。是否可能以及如何实现？
回答by Evgeni Dimitrov
There is an open Jira for this: https://jira.spring.io/browse/SPR-6736
为此有一个开放的 Jira：https: //jira.spring.io/browse/SPR-6736
The workaround is to use @Beanin @Configurationclass:
解决方法是@Bean在@Configuration课堂上使用：
@Configuration
public class AppConfig {
@Bean(name = { "dataSource", "subsystemA-dataSource", "subsystemB-dataSource" })
public MyService myService() {}
}
回答by herau
If you want to use the placeholder, another workaround is to use @Bean in a @Configuration class using @Value and the Spring applicationContext.
如果要使用占位符，另一种解决方法是使用 @Value 和 Spring applicationContext 在 @Configuration 类中使用 @Bean。
@Configuration
public class AppConfig {
@Autowired
private ApplicationContext context;
@Bean
public MyService myService(@Value("${myService.qualifier}") String qualifier) {
return (MyService) context.getBean(qualifier);
}
}
NB : special consideration must be taken for the placeholder bean which must be loaded at the beginning (cf javadoc)
注意：必须特别考虑必须在开头加载的占位符 bean (cf javadoc)
回答by jankovd
With small amount of configuration and one ImportBeanDefinitionRegistraryou can configure bean aliases via Java configuration. You can check bean-aliaslibrary project for reference - developed for the needs of my projects. Feel free to modify and/or copy the source into your own project in case the spring version used in it does not work with your setup.
ImportBeanDefinitionRegistrar只需少量配置，您就可以通过 Java 配置配置 bean 别名。您可以查看bean-alias库项目以供参考 - 为我的项目需要而开发。随意修改和/或将源代码复制到您自己的项目中，以防其中使用的 spring 版本不适用于您的设置。
Once you have the library on your path, you declare an alias through the annotation:
一旦你的路径上有了库，你就可以通过注释声明一个别名：
@Configuration
@BeanAlias(name = "fromName", alias = "toName")
public class ExampleConfiguration {
}
That's it.
而已。
How it works is that with the annotation we import a ImportBeanDefinitionRegistrarimplementation
它的工作原理是使用注释导入一个ImportBeanDefinitionRegistrar实现
@Import(BeanAliasBeanRegistrar.class)
public @interface BeanAlias {
}
which registers the alias in the BeanDefinitionRegistry
它将别名注册在 BeanDefinitionRegistry
class BeanAliasBeanRegistrar implements ImportBeanDefinitionRegistrar, PriorityOrdered {
@Override
public void registerBeanDefinitions(AnnotationMetadata metadata, BeanDefinitionRegistry registry) {
...
registerAlias(registry, metadata.getAnnotationAttributes(BeanAlias.class.getName()));
}
private void registerAlias(BeanDefinitionRegistry registry, Map<String, Object> attributes) {
...
registry.registerAlias(name, alias);
}
}
