Question

bar

Spring.xml

public class Car {
    @Qualifier("e2")
    @Autowired  
    private Engine engine;

    public void printData() {
        System.out.println("Engine object ref "+engine.getModelOfYear());
        }
}

public class Engine {

    private String modelOfYear;

    public String getModelOfYear() {
        return modelOfYear;
    }
    public void setModelOfYear(String modelOfYear) {
        this.modelOfYear = modelOfYear;
    }
}

测试课

<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN 2.0//EN" "http://www.springframework.org/dtd/spring-beans-2.0.dtd">
<beans>
<bean class="org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor"/>
    <bean id="e1" class="beans.Engine">
        <property name="modelOfYear" value="2013"/>
    </bean>
    <bean id="e2" class="beans.Engine">
        <property name="modelOfYear" value="2011"/>
    </bean>
    <bean id="c1" class="beans.Car"/>
</beans>

我总是遇到的例外

引起： org.springframework.beans.factory.NoUniqueBeanDefinitionException：没有 bean类型的限定豆类.Engine＆＃39;可用：预期单身匹配bean但找到2：e1，e2 在org.springframework.beans.factory.config.DependencyDescriptor.resolveNotUnique（DependencyDescriptor.java:215） at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency（DefaultListableBeanFactory.java:1116）在org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency（DefaultListableBeanFactory.java:1065） at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor $ AutowiredFieldElement.inject（AutowiredAnnotationBeanPostProcessor.java:584） ......还有15个

Answer 1

您正在将注释与xml配置混合。

您在XML中声明了您的bean Car，但是通过注释声明了@Qualifier，因此它不起作用。

替换

<bean id="c1" class="beans.Car"/>

使用：

<bean id="c1" class="beans.Car">
      <property name="engine" ref="e2"/>
</bean>

或者完全删除xml配置并使用完全注释（这是首选并现在推荐）

Answer 2

让Spring处理XML声明bean中的@Autowired注释，将<context:annotation-config/>添加到Spring.xml：

<?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:annotation-config/>

    <bean id="e1" class="beans.Engine">
        <property name="modelOfYear" value="2013"/>
    </bean>
    <bean id="e2" class="beans.Engine">
        <property name="modelOfYear" value="2011"/>
    </bean>
    <bean id="c1" class="beans.Car"/>
</beans>

使用@Qualifier仍然会得到UnsatisfiedDependency Exception，任何人都可以帮助我

2 个答案: