[英]Spring inject without autowire annotation
I find some answer: https://stackoverflow.com/a/21218921/2754014 about Dependency Injection.我找到了一些答案: https : //stackoverflow.com/a/21218921/2754014关于依赖注入。 There isn't any annotation like
@Autowired
, @Inject
or @Resource
.没有像
@Autowired
、 @Inject
或@Resource
这样的注释。 let's assume that there isn't any XML configuration for this example TwoInjectionStyles
bean (except simple <context:component-scan base-package="com.example" />
.让我们假设这个示例
TwoInjectionStyles
bean 没有任何 XML 配置(除了简单的<context:component-scan base-package="com.example" />
。
Is it correct to inject without specify annotation?在没有指定注释的情况下注入是否正确?
From Spring 4.3 annotations are not required for constructor injection.从 Spring 4.3 开始,构造函数注入不需要注解。
public class MovieRecommender {
private CustomerPreferenceDao customerPreferenceDao;
private MovieCatalog movieCatalog;
//@Autowired - no longer necessary
public MovieRecommender(CustomerPreferenceDao customerPreferenceDao) {
this.customerPreferenceDao = customerPreferenceDao;
}
@Autowired
public setMovieCatalog(MovieCatalog movieCatalog) {
this.movieCatalog = movieCatalog;
}
}
But you still need @Autowired
for setter injection.但是你仍然需要
@Autowired
来进行 setter 注入。 I checked a moment ago with Spring Boot 1.5.7
(using Spring 4.3.11
) and when I removed @Autowired
then bean was not injected.我刚才检查了
Spring Boot 1.5.7
(使用Spring 4.3.11
),当我删除@Autowired
bean 没有被注入。
Yes, example is correct (starting from Spring 4.3 release).是的,示例是正确的(从 Spring 4.3 版本开始)。 According to the documentation ( this for ex), if a bean has single constructor,
@Autowired
annotation can be omitted.根据文档(例如this ),如果 bean 具有单个构造函数,则可以省略
@Autowired
注释。
But there are several nuances:但是有几个细微差别:
1. When single constructor is present and setter is marked with @Autowired
annotation, than both constructor & setter injection will be performed one after another: 1.当存在单个构造函数并且setter被
@Autowired
注解标记时,构造函数和setter注入将@Autowired
执行:
@Component
public class TwoInjectionStyles {
private Foo foo;
public TwoInjectionStyles(Foo f) {
this.foo = f; //Called firstly
}
@Autowired
public void setFoo(Foo f) {
this.foo = f; //Called secondly
}
}
2. At the other hand, if there is no @Autowire
at all (as in your example ), than f
object will be injected once via constructor, and setter can be used in it's common way without any injections. 2.另一方面,如果根本没有
@Autowire
(如您的示例),那么f
对象将通过构造函数注入一次,并且 setter 可以在没有任何注入的情况下以常见方式使用。
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