在 Spring 中定义 java.util.Queue bean 的正确方法？

Question

当我尝试使用

java.util.Queue

注入

Spring Core

bean 时，我遇到了一个奇怪的错误。

我做了一个快速代码示例：

@Configuration public class Main {
    @Autowired private Queue<Service> serviceQueue;

    public static void main(String[] args) {
        ApplicationContext context = new AnnotationConfigApplicationContext(Main.class);
        Main bean = context.getBean(Main.class);
        System.out.println(bean.serviceQueue.size());
    }

    @Bean public Queue<Service> serviceQueue() {
        Queue<Service> serviceQueue = new ArrayDeque<>();
        serviceQueue.add(serviceImpl1());
        serviceQueue.add(serviceImpl2());
        return serviceQueue;
    }

    @Bean public Service serviceImpl1() { return new ServiceImpl1(); }
    @Bean public Service serviceImpl2() { return new ServiceImpl2(); }

    public interface Service {}
    public static class ServiceImpl1 implements Service {}
    public static class ServiceImpl2 implements Service {}
}

当我运行这段代码时，我在控制台中收到下一个错误：

Feb 23, 2023 8:59:48 PM org.springframework.context.support.AbstractApplicationContext refresh
WARNING: Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'main': Unsatisfied dependency expressed through field 'serviceQueue'; nested exception is org.springframework.beans.ConversionNotSupportedException: Failed to convert value of type 'java.util.LinkedHashMap$LinkedValues' to required type 'java.util.Queue'; nested exception is java.lang.IllegalStateException: Cannot convert value of type 'java.util.LinkedHashMap$LinkedValues' to required type 'java.util.Queue': no matching editors or conversion strategy found
Exception in thread "main" org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'main': Unsatisfied dependency expressed through field 'serviceQueue'; nested exception is org.springframework.beans.ConversionNotSupportedException: Failed to convert value of type 'java.util.LinkedHashMap$LinkedValues' to required type 'java.util.Queue'; nested exception is java.lang.IllegalStateException: Cannot convert value of type 'java.util.LinkedHashMap$LinkedValues' to required type 'java.util.Queue': no matching editors or conversion strategy found
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.resolveFieldValue(AutowiredAnnotationBeanPostProcessor.java:660)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:640)
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:119)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessProperties(AutowiredAnnotationBeanPostProcessor.java:399)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1431)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:619)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:542)
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:335)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:333)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:208)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:955)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:918)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:583)
    at org.springframework.context.annotation.AnnotationConfigApplicationContext.<init>(AnnotationConfigApplicationContext.java:93)
    at app.Main.main(Main.java:16)
Caused by: org.springframework.beans.ConversionNotSupportedException: Failed to convert value of type 'java.util.LinkedHashMap$LinkedValues' to required type 'java.util.Queue'; nested exception is java.lang.IllegalStateException: Cannot convert value of type 'java.util.LinkedHashMap$LinkedValues' to required type 'java.util.Queue': no matching editors or conversion strategy found
    at org.springframework.beans.TypeConverterSupport.convertIfNecessary(TypeConverterSupport.java:76)
    at org.springframework.beans.TypeConverterSupport.convertIfNecessary(TypeConverterSupport.java:45)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveMultipleBeans(DefaultListableBeanFactory.java:1471)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1349)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1311)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.resolveFieldValue(AutowiredAnnotationBeanPostProcessor.java:657)
    ... 15 more
Caused by: java.lang.IllegalStateException: Cannot convert value of type 'java.util.LinkedHashMap$LinkedValues' to required type 'java.util.Queue': no matching editors or conversion strategy found
    at org.springframework.beans.TypeConverterDelegate.convertIfNecessary(TypeConverterDelegate.java:262)
    at org.springframework.beans.TypeConverterSupport.convertIfNecessary(TypeConverterSupport.java:73)
    ... 20 more

你能解释一下为什么我不能创建这样的

Queue

吗？如果我将

Queue

替换为

List

，一切都会起作用。

谢谢。