如何在 kotlin 中使用像 @Autowired 这样的 spring 注释？
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How to use spring annotations like @Autowired in kotlin?
提问by eendroroy
Is it possible to do something like following in Kotlin?
是否可以在 Kotlin 中执行以下操作？
@Autowired
internal var mongoTemplate: MongoTemplate
@Autowired
internal var solrClient: SolrClient
回答by Ruslan
Recommended approach to do Dependency Injection in Spring is constructor injection:
在 Spring 中进行依赖注入的推荐方法是构造函数注入：
@Component
class YourBean(
private val mongoTemplate: MongoTemplate,
private val solrClient: SolrClient
) {
// code
}
Prior to Spring 4.3 constructor should be explicitly annotated with Autowired:
在 Spring 4.3 构造函数之前，应显式注释Autowired：
@Component
class YourBean @Autowired constructor(
private val mongoTemplate: MongoTemplate,
private val solrClient: SolrClient
) {
// code
}
In rare cases, you might like to use field injection, and you can do it with the help of lateinit:
在极少数情况下，您可能喜欢使用字段注入，您可以在以下帮助下进行lateinit：
@Component
class YourBean {
@Autowired
private lateinit var mongoTemplate: MongoTemplate
@Autowired
private lateinit var solrClient: SolrClient
}
Constructor injection checks all dependencies at bean creation time and all injected fields is val, at other hand lateinit injected fields can be only var, and have little runtime overhead. And to test class with constructor, you don't need reflection.
构造函数注入在 bean 创建时检查所有依赖项，所有注入的字段 is val，另一方面，lateinit 注入的字段只能是var，并且运行时开销很小。并且要使用构造函数测试类，您不需要反射。
Links:
链接：
回答by Mike Buhot
Yes, java annotations are supported in Kotlin mostly as in Java. One gotcha is annotations on the primary constructor requires the explicit 'constructor' keyword:
是的，与 Java 一样，Kotlin 主要支持 Java 注释。一个问题是主构造函数上的注释需要显式的 'constructor' 关键字：
From https://kotlinlang.org/docs/reference/annotations.html
来自https://kotlinlang.org/docs/reference/annotations.html
If you need to annotate the primary constructor of a class, you need to add the constructor keyword to the constructor declaration, and add the annotations before it:
如果需要对类的主构造函数进行注解，则需要在构造函数声明中添加constructor关键字，并在其前添加注解：
class Foo @Inject constructor(dependency: MyDependency) {
// ...
}
回答by Mr.Turtle
You can also autowire dependencies through the constructor. Remember to annotate your dependencies with @Configuration, @Component, @Serviceetc
您还可以通过构造函数自动装配依赖项。记得用@Configuration, @Component, @Serviceetc注释你的依赖项
import org.springframework.stereotype.Component
@Component
class Foo (private val dependency: MyDependency) {
//...
}
