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不起作用。我看到错误，他甚至做不了什么。

DOG

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);
}

}

TEST CLASS

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

需要帮助

Answer 1

可能您的ApplicationContext BeanFactory配置了默认 AutowireCandidateResolver（即SimpleAutowireCandidateResolver）而不是QualifierAnnotationAutowireCandidateResolver }。

在以前版本的 Spring （4.0之前）中，在创建大多数ApplicationContexts（比较QualifierAnnotationAutowireCandidateResolver实现）期间设置了AbstractRefreshableApplicationContext.customizeBeanFactory(DefaultListableBeanFactory) 。

目前，AppCtx的QualifierAnnotationAutowireCandidateResolver可以通过以下方式应用：

org.springframework.beans.factory.annotation.CustomAutowireConfigurer （请参阅javadoc和postProcessBeanFactory(ConfigurableListableBeanFactory)方法的实施），例如添加到您的xml：

<bean id="customAutowireConfigurer" class="org.springframework.beans.factory.annotation.CustomAutowireConfigurer">
<property name="customQualifierTypes">
    <set>
        <value>org.springframework.beans.factory.annotation.Qualifier</value>
    </set>
</property>

<context:annotation-config /> （请参阅：AnnotationConfigBeanDefinitionParser.parse(Element,ParserContext)及相关的）

Answer 2

@Qualifier用于通过名称或id引用bean。因为它无法找到名称或ID为＆＃39;小＆＃39;的xml条目。它尝试按类型进行匹配，它找到了两个Size实例。

以下方法可行：

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

虽然看起来您希望将Size实例视为预先配置的bean。如果是这种情况你可以在你的xml文件中声明Dog的实例并引用Size beans ......就像这样：

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

Answer 3

@Qualifier（name =＆＃34; ..＆＃34;）注释，并给出我们希望Spring注入的bean的名称

并且您的bean的名称是size1和size2。

所以试试

   @Qualifier("size1")

Answer 4

@Qualifier（“small”）意味着你要找一个名为“small”的bean（bean id =“small”......）@Autowired意味着你要找一个匹配类型的bean。

在某些情况下，将这两种配置结合使用是有意义的。这意味着：寻找一个名为that的bean，如果找不到，那么找一个具有正确类型的bean。这非常强大。

从Spring documentation开始，您可以像使用xml限定符一样声明谁是“小”。但是在他们的例子中有NO id =“...”我不知道定义限定符和id是否有意义。所以我想（我不测试）你可以通过删除部分id =“sizeX”

来修复你的例子

Answer 5

正如您所说的堆栈跟踪

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

Spring无法匹配单个bean来注入，因为他找到了2个可以使用的bean，因此会抛出此异常。

当向BeanFactory请求bean实例时抛出异常当只有一个时，找到了多个匹配的候选者期待匹配的豆。

Reference of Exception

无论如何你以错误的方式使用这个东西，因为没有id="small"

的bean

您必须将@Qualifier("small")更改为@Qualifier("size1")或@Qualifier("size2")。

Answer 6

在Spring 4.x中，您应该使用以下XML架构，以便它可以为您服务：

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-4.0.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd"

您应该添加以下标记：

<context:component-scan base-package="com.tests.test2" />

所以下面的XML应该可以解决你的问题（它解决了我的问题:)）：

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

    <context:component-scan base-package="com.tests.test2" />

    <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>
</beans>

查看更多here。

Answer 7

我们的项目中使用了Spring 3.x的struts 1.x.在从spring 3＆gt; 4升级的过程中，我们在struts动作中的限定符注释不再起作用。在深入挖掘并比较Spring 3和4之后，终于找到了原因。

reason1：QualifierAnnotationAutowireCandidateResolver不是春季4的默认解析器

在Spring 3中，在我们在应用程序上下文中创建beanfacotry之后，Spring将显式调用：

beanFactory.setAutowireCandidateResolver(new QualifierAnnotationAutowireCandidateResolver());

在Spring 4中，在AbstractRefreshableApplicationContext的

中不再调用它

protected void customizeBeanFactory(DefaultListableBeanFactory beanFactory)

因此对于父（root）上下文，如果你在config xml中有它，它应该仍然可以工作。但是对于子上下文，默认解析器将变为“SimpleAutowireCandidateResolver”

reason2：在Spring 4的DefaultListableBeanFactory

中尝试确定'isAutowireCandidate（）'时，子解析器被传递给父级

如果无法做出决定，isAutowireCandidate（）会将责任委托给父beanFactory。

在Spring 3中，委托不会将解析器传递给父级，以便父上下文使用自己的解析器来调用isAutowireCandidate（）。然而在春季4，它发生了变化。解析器作为参数传递给使用它来调用isAutowireCandidate（）的父级。因此，即使父母有一个ContextAnnotationAutowireCandidateResolver，它将QualifierAnnotationAutowireCandidateResolver扩展为其解析器，它仍然无济于事。

如果将@ a5phyx解决方案添加到子的应用程序上下文xml中，它应该可以正常工作。

Answer 8

尝试在beans.xml文件中使用此bean定义：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:security="http://www.springframework.org/schema/security"
    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
        http://www.springframework.org/schema/security
        http://www.springframework.org/schema/security/spring-security.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd"
        xmlns:context="http://www.springframework.org/schema/context">

    <context:annotation-config/>
    <!-- define your beans here-->
</beans>

Spring 4.1 @Qualifier不起作用

8 个答案: