Spring @Resource、@Autowired、@Qualifier的注解注入及区别

╰半橙微兮° 2022-08-09 09:48 132阅读 0赞

spring2.5提供了基于注解（Annotation-based）的配置，我们可以通过注解的方式来完成注入依赖。在Java代码中可以使用 @Resource或者@Autowired注解方式来经行注入。虽然@Resource和@Autowired都可以来完成注入依赖，但它们之间是有区 别的。首先来看一下：

a.@Resource默认是按照名称来装配注入的，只有当找不到与名称匹配的bean才会按照类型来装配注入；

b.@Autowired默认是按照类型装配注入的，如果想按照名称来转配注入，则需要结合@Qualifier一起使用；

c.@Resource注解是又J2EE提供，而@Autowired是由Spring提供，故减少系统对spring的依赖建议使用

@Resource的方式；

d. @Resource和@Autowired都可以书写标注在字段或者该字段的setter方法之上

因为本人使用的全是注解，配置文件就不在写出。

1.Resource 使用方法

@Resource(name="userDao")  
      private UserDao<Suser> userDao;

2.Autowire 使用方法

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  </tr> 
 </tbody> 
</table>

在java代码中可以使用@Autowire或者@Resource注解方式进行装配，这两个注解的区别是：  
@Autowire 默认按照类型装配，默认情况下它要求依赖对象必须存在如果允许为null，可以设置它required属性为false，如果我们想使用按照名称装配，可 以结合@Qualifier注解一起使用;(一般不推荐使用)

@Resource默认按照名称装配，当找不到与名称匹配的bean才会按照类型装配，可以通过name属性指定，如果没有指定name属 性，当注解标注在字段上，即默认取字段的名称作为bean名称寻找依赖对象，当注解标注在属性的setter方法上，即默认取属性名作为bean名称寻找 依赖对象.

注意：如果没有指定name属性，并且按照默认的名称仍然找不到依赖的对象时候，会回退到按照类型装配，但一旦指定了name属性，就只能按照名称 装配了.