java @autowired 注释如何用于私有字段？
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How does @autowired annotation works for a private field?
提问by Vishnudev K
How does @Autowiredannotation work for a private field without a getter and a setter?
How can spring access a private field?
@Autowired注释如何在没有 getter 和 setter 的情况下为私有字段工作？spring如何访问私有字段？
回答by wastl
It works with reflection. Hereyou can find an example of how to set public fields. But setting private fields does not make much of a difference
它适用于反射。您可以在此处找到有关如何设置公共字段的示例。但是设置私有字段并没有太大区别
The only difference with a private field is that you will need to set the setAccessible before you are able to read/write to the field. Further, this method can throw a SecurityException. Java Docs
与私有字段的唯一区别是您需要先设置 setAccessible，然后才能读/写该字段。此外，此方法可以抛出 SecurityException。 Java 文档
回答by anurag gupta
@Component
public class A(){}
@Component
public class B(){
@Autowired
private A a;
}
Spring create beans mentioned as @Component. here bean A will be created first and since B is dependent on A, then injection of A to B is done. there's no need for any setters. just @Component is required. Spring uses CGLib for creation of beans using reflection.
Spring 创建以@Component 命名的 bean。这里首先创建 bean A 并且由于 B 依赖于 A，然后将 A 注入到 B 完成。不需要任何二传手。只需要@Component。Spring 使用 CGLib 通过反射创建 bean。
回答by Rajesh
Three types of dependency injection
依赖注入的三种类型
There are at least three ways an object can receive a reference to an external module:
对象至少可以通过三种方式接收对外部模块的引用：
constructor injection:the dependencies are provided through a class constructor.
构造函数注入：依赖项通过类构造函数提供。
setter injection:the client exposes a setter method that the injector uses to inject the dependency.
setter 注入：客户端公开一个 setter 方法，注入器使用该方法注入依赖项。
interface injection:the dependency provides an injector method that will inject the dependency into any client passed to it. Clients must implement an interface that exposes a setter method that accepts the dependency.
接口注入：依赖提供了一个注入器方法，该方法将依赖注入任何传递给它的客户端。客户端必须实现一个接口，该接口公开接受依赖项的 setter 方法。
