在春季，'autowire = Autowire.NO'是做什么的？ [英] In Spring, what does 'autowire = Autowire.NO' do?

问题描述

来自这个Spring文档我知道当我使用@Bean时，默认值已经等效于：

From this Spring documentation I know that when I use @Bean, the default is already equivalent to:

@Bean（autowire = Autowire.NO）

@Bean(autowire = Autowire.NO)

（默认）无自动装配。 Bean引用必须通过ref元素定义。对于大型部署，建议不要更改默认设置，因为明确指定协作者可以提供更好的控制和清晰度。在某种程度上，它记录了系统的结构。

(Default) No autowiring. Bean references must be defined via a ref element. Changing the default setting is not recommended for larger deployments, because specifying collaborators explicitly gives greater control and clarity. To some extent, it documents the structure of a system.

我只是想了解这对我意味着什么。如果我的系统是100％Java Config 并且没有XML配置，那么据我所知，当我使用@Bean时， Autowire.no不会产生任何影响。

I am just trying to understand what this means for me. If my system is 100% Java Config and has no XML configuration, then from what I can tell, when I use @Bean, the 'Autowire.no' has no impact whatsoever.

编辑

没有影响是指其他@Autowired引用到该bean的是自动装配的（在其他Java Config类中）。我怀疑这是因为在Java Config中没有定义显式的 ref元素，所以此（默认）设置无效。

By "no impact" I mean that other @Autowired references to this bean ARE autowired (in other Java Config classes). I suspect that is because with Java Config there is no explicit 'ref element' defined, so this (default) setting has no effect.

示例：

第一个配置：

package a.b.c;

@Configuration
public class AlphaConfig {

    @Bean(autowire = Autowire.NO)
    public AlphaBeanType alphaBean() {
        return new AlphaBeanType();
    }
}

然后在第二个配置中：

package d.e.f;

import a.b.c.AlphaBeanType;

@Configuration
public class AnotherConfig {

    @Autowire
    private AlphaBeanType alphaBeanType;

    @Bean
    . . .
}

我看到的是'alphaBeanType'总是自动连接到第二个配置类中-似乎与文档冲突-因此是我的问题。

What I see is that 'alphaBeanType' is always autowired in the second config class - which seems to be in conflict with the documentation - hence my question.

最终编辑

当然，我不能完全从文档中得知！有人确定吗？

Of course, I can't quite tell from the documentation! Does anyone know for sure?

推荐答案

设置 Autowire.NO 不会表示该豆不能通过 @Autowire 注入其他豆中。 @Autowire 默认情况下按类型工作，也可以使用 @Qualifier 按名称工作。

Setting Autowire.NO does not mean that the bean cannot be injected in other beans via @Autowire. @Autowire works by default by type, and can also work by name using @Qualifier.

因此，如果您的bean具有正确的类型或名称，它将被注入其他bean中，这是正常的。

So if your bean has the right type or name, it will get inject in other beans, that's normal.

Autowire.NO 的含义类似于：

不要注入 THIS 使用 @Bean 声明的bean，无论是类型还是名称。如果未在 @Bean 方法代码中设置Bean属性，请将其保留为空。

Don't inject the properties of THIS bean being declared with @Bean neither by type or by name. If the bean properties are not set in the @Bean method code, leave them unfilled.

这是一个如何工作的代码示例，让我们定义两个bean：

This a code example of how this works, let's define two beans:

public class MyBeanTwo {

    public MyBeanTwo() {
        System.out.println(">>> MY Bean 2 created!");
    }
}

public class MyBean {

    private MyBeanTwo myBeanTwo;

    public MyBean() {
        System.out.println(">>>MyBean created !!");
    }

    public void setMyBeanTwo(MyBeanTwo myBeanTwo) {
        System.out.println(">>> Injecting MyBeanTwo INTO MyBeanOne !!!");
        this.myBeanTwo = myBeanTwo;
    }
}

和某些配置：

@Configuration
public class SimpleConfigOne {

    @Bean
    public MyBean createMyBean()   {
        return new MyBean();
    }

    @Bean
    public MyBeanTwo createMyBeanTwo() {
        return new MyBeanTwo();
    }
}

使用此配置，此应用程序的启动将为日志：

With this configuration, the startup of this application gives this log:

>>>MyBean created !!
>>> MY Bean 2 created!

每个Bean均创建了一个实例，但 MyBean 没有注入 MyBeanTwo ，即使存在具有正确类型的强韧豆。

Meaning one instance of each bean was created, but MyBean did NOT get injected with MyBeanTwo, even tough a bean with the correct type existed.

通过声明 MyBean 像这样：

@Bean(autowire = Autowire.BY_TYPE)
public MyBean createMyBean()   {
    return new MyBean();
}

MyBeanOne 现在可以通过按类型自动装配来设置其属性。

MyBeanOne is now eligible to have it's properties set via autowiring by type.

启动日志变为：

>>>MyBean created !!
>>> MY Bean 2 created!
>>> Injecting MyBeanTwo INTO MyBeanOne !!!

这表明 MyBean 的 MyBeanTwo 通过按类型注入按类型进行注入。

This shows that MyBean had MyBeanTwo injected by type via a by type injection.

为什么使用Autowire.NO是默认值：

通常，我们不想自动连接使用 @Bean 创建的bean的属性。我们通常要做的是通过代码显式设置属性以提高可读性，作为一种文档形式，并确保将属性设置为正确的值。

Usually we don't want to autowire the properties of beans created with @Bean. What we usually do is set the properties explicitly via code for readability, as a form of documentation and to make sure the property is set with the correct value.

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