显示目录

Qualifier

当找到多个同类型的 Bean 的定义时,@Autowired 注入的时候不知道要用哪一个,会报异常,可以使用 @Qualifier 指定要注入的 Bean。

@Resource 相当于 @Autowired 和 @Qualifier 的组合。

spring-beans.xml

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<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd">
<context:component-scan base-package="com.xtuer.beans"/>
<bean id="door1" class="com.xtuer.beans.Door"/>
<bean id="door2" class="com.xtuer.beans.Door"/>
</beans>

House

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package com.xtuer.beans;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Component;
// 生成的 Bean 的 ID 是 house
@Component
public class House {
private String description;
@Autowired
@Qualifier("door1") // 注入标志为 door1 的 Bean
private Door door;
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
public Door getDoor() {
return door;
}
public void setDoor(Door door) {
this.door = door;
}
}