java - 为什么 NoUniqueBeanDefinitionException：没有定义类型的限定 bean：预期单个匹配 bean 但找到 2

Question

在这个小应用程序中，我使用@Autowired注解和@Qualifier注解来配置依赖项，但仍然抛出异常，如下所述。

比萨类

public class Pizza {

    private Address deliverydest;

    @Autowired
    @Qualifier("ForPizza")
    public void setDeliverydest(Address deliverydest) {
        this.deliverydest = deliverydest;
    }
}

Spring 上下文配置

<?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-3.0.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd">

    <bean id="pizza" class="com.test.Shopping.Pizza" />

    <bean id="Cust1Address" class="com.test.Shopping.Address" />

    <bean id="dest1" class="com.test.Shopping.Address" >
        <qualifier value="ForPizza" />
        <property name="buildingno" value="flat1/door2" />
    </bean>

    <bean class="org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor" />

</beans>

抛出的异常是

Exception in thread "main" org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'pizza': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire method: public void com.test.Shopping.Pizza.setDeliverydest(com.test.Shopping.Address); nested exception is org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type [com.test.Shopping.Address] is defined: expected single matching bean but found 2: Cust1Address,dest1

Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire method: public void com.test.Shopping.Pizza.setDeliverydest(com.test.Shopping.Address); nested exception is org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type [com.test.Shopping.Address] is defined: expected single matching bean but found 2: Cust1Address,dest1

Caused by: org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type [com.test.Shopping.Address] is defined: expected single matching bean but found 2: Cust1Address,dest1

.

现在为什么 Spring 不考虑@Qualifier注释来找到具有 qualifier的正确 bean dest1value="ForPizza"？

Answer 1

尝试将以下内容添加到您的 Spring 配置中：

<context:annotation-config/>
<context:component-scan base-package="com.test.Shopping"/>

Answer 2

尝试放置@Qualifier在参数而不是方法上：

@Autowired
public void setDeliverydest(@Qualifier("ForPizza") Address deliverydest) { ... }

Answer 3

删除所有注释 bean 后处理器，只需在 xml 中添加以下内容。

<context:annotation-config/>