Spring 4.1 @Qualifier不起作用

Question

我有这样的类，xml配置文件和错误堆栈跟踪。我不知道为什么@Qualifier无法正常工作。我看到他甚至什么都不做的错误。

狗

public class SimpleDog implements Dog {
    @Autowired
    @Qualifier("small")
    private Size size;
    private String name;

public Size getSize() {
    return size;
}

public void setSize(Size size) {
    this.size = size;
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

@Override
public void giveSound() {
    System.out.println("dog size is : width : (" + size.getWidth() + ") , height : (" + size.getHeight() + ")");
    System.out.println("dog's name : " + name);
}

}

考试班

public class Test2 {
public static void main(String[] args) {
    ApplicationContext context = new ClassPathXmlApplicationContext("spring-test2.xml");
    SimpleDog dog = (SimpleDog) context.getBean("dog");
    dog.giveSound();
}

}

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"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="dog" class="com.tests.test2.SimpleDog">
         <property name="name" value="Puppy" />
    </bean>

    <bean id="size1" class="com.tests.test2.Size">
        <qualifier value="small"/>
        <property name="height" value="2"/>
        <property name="width" value="1"/>
    </bean>

    <bean id="size2" class="com.tests.test2.Size">
        <qualifier value="large"/>
        <property name="height" value="20"/>
        <property name="width" value="10"/>
    </bean>

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

错误堆栈跟踪

WARNING: Exception encountered during context initialization - cancelling refresh attempt
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dog': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private com.tests.test2.Size com.tests.test2.SimpleDog.size; nested exception is org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type [com.tests.test2.Size] is defined: expected single matching bean but found 2: size1,size2
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:334)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1204)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:538)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:476)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:302)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:229)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:298)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:193)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:725)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:757)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:480)
    at org.springframework.context.support.FileSystemXmlApplicationContext.<init>(FileSystemXmlApplicationContext.java:140)
    at org.springframework.context.support.FileSystemXmlApplicationContext.<init>(FileSystemXmlApplicationContext.java:84)
    at pl.patrykgryta.test2.Test2.main(Test2.java:12)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:134)
Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: private com.tests.test2.Size com.tests.test2.SimpleDog.size; nested exception is org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type [com.tests.test2.Size] is defined: expected single matching bean but found 2: size1,size2
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:555)
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:87)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:331)
    ... 18 more
Caused by: org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type [com.tests.test2.Size] is defined: expected single matching bean but found 2: size1,size2
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1016)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:904)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:527)
    ... 20 more

Exception in thread "main" org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dog': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private com.tests.test2.Size com.tests.test2.SimpleDog.size; nested exception is org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type [com.tests.test2.Size] is defined: expected single matching bean but found 2: size1,size2
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:334)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1204)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:538)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:476)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:302)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:229)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:298)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:193)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:725)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:757)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:480)
    at org.springframework.context.support.FileSystemXmlApplicationContext.<init>(FileSystemXmlApplicationContext.java:140)
    at org.springframework.context.support.FileSystemXmlApplicationContext.<init>(FileSystemXmlApplicationContext.java:84)
    at pl.patrykgryta.test2.Test2.main(Test2.java:12)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:134)
Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: private com.tests.test2.Size com.tests.test2.SimpleDog.size; nested exception is org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type [com.tests.test2.Size] is defined: expected single matching bean but found 2: size1,size2
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:555)
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:87)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:331)
    ... 18 more
Caused by: org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type [com.tests.test2.Size] is defined: expected single matching bean but found 2: size1,size2
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1016)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:904)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:527)
    ... 20 more

需要帮忙

Answer 1

@Qualifier用于通过其名称或ID引用bean。由于无法找到名称或ID为“
small”的xml条目，因此它尝试按类型进行匹配，并找到了两个Size实例。

以下将起作用：

  <bean id="small" class="com.tests.test2.Size">      
    <property name="height" value="2"/>
    <property name="width" value="1"/>
</bean>

虽然看起来您还是想将Size实例视为预配置的bean。如果是这种情况，您可以在xml文件中声明Dog的实例，并引用Size Bean …类似这样：

  <bean id="rex" class="com.tests.test2.SimpleDog">
     <property name="name" value="Puppy" />
     <property name="size" ref="size1"/>
  </bean>