尽管我相信存在一个bean[duplicate]，但没有这样的bean定义异常

Question

当我尝试运行Spring Boot应用程序时，出现了这个错误

org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'org.springframework.data.mongodb.core.MongoOperations' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {}
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoMatchingBeanFound(DefaultListableBeanFactory.java:1714) ~[spring-beans-5.2.7.RELEASE.jar:5.2.7.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1270) ~[spring-beans-5.2.7.RELEASE.jar:5.2.7.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1224) ~[spring-beans-5.2.7.RELEASE.jar:5.2.7.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.resolveAutowiredArgument(ConstructorResolver.java:884) ~[spring-beans-5.2.7.RELEASE.jar:5.2.7.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:788) ~[spring-beans-5.2.7.RELEASE.jar:5.2.7.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:538) ~[spring-beans-5.2.7.RELEASE.jar:5.2.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1338) ~[spring-beans-5.2.7.RELEASE.jar:5.2.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1177) ~[spring-beans-5.2.7.RELEASE.jar:5.2.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:557) ~[spring-beans-5.2.7.RELEASE.jar:5.2.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:517) ~[spring-beans-5.2.7.RELEASE.jar:5.2.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:323) ~[spring-beans-5.2.7.RELEASE.jar:5.2.7.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:226) ~[spring-beans-5.2.7.RELEASE.jar:5.2.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:321) ~[spring-beans-5.2.7.RELEASE.jar:5.2.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) ~[spring-beans-5.2.7.RELEASE.jar:5.2.7.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:893) ~[spring-beans-5.2.7.RELEASE.jar:5.2.7.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:879) ~[spring-context-5.2.7.RELEASE.jar:5.2.7.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:551) ~[spring-context-5.2.7.RELEASE.jar:5.2.7.RELEASE]
    at org.springframework.boot.web.reactive.context.ReactiveWebServerApplicationContext.refresh(ReactiveWebServerApplicationContext.java:62) ~[spring-boot-2.3.1.RELEASE.jar:2.3.1.RELEASE]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:758) [spring-boot-2.3.1.RELEASE.jar:2.3.1.RELEASE]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:750) [spring-boot-2.3.1.RELEASE.jar:2.3.1.RELEASE]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397) [spring-boot-2.3.1.RELEASE.jar:2.3.1.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:315) [spring-boot-2.3.1.RELEASE.jar:2.3.1.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1237) [spring-boot-2.3.1.RELEASE.jar:2.3.1.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226) [spring-boot-2.3.1.RELEASE.jar:2.3.1.RELEASE]
    at com.greglturnquist.learningspringboot2.learningspringboot2.LearningSpringBoot2Application.main(LearningSpringBoot2Application.java:12) [main/:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_121]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_121]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_121]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_121]
    at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49) [spring-boot-devtools-2.3.1.RELEASE.jar:2.3.1.RELEASE]

就我所知，我的代码如下，我有一个MongoOperationsbean：

@Component
public class InitDatabase {
    @Bean
    CommandLineRunner init(MongoOperations operations) {
        return args -> {
            // tag::log[]
            operations.dropCollection(Image.class);

            operations.insert(new Image("1",
                "learning-spring-boot-cover.jpg"));
            operations.insert(new Image("2",
                "learning-spring-boot-2nd-edition-cover.jpg"));
            operations.insert(new Image("3",
                "bazinga.png"));

            operations.findAll(Image.class).forEach(image -> {
                System.out.println(image.toString());
            });
            // end::log[]
        };
    }
}

我做错了什么？

Answer 1

我认为您可能错误地使用了@Component注释来声明配置类，请使用@Configuration来代替：

@Configuration
public class InitDatabase {
    @Bean
    CommandLineRunner init(MongoOperations operations) {
        return args -> {
            ...
        };
    }
}

从文件中：

配置：表示一个类声明了一个或多个@Bean方法，并且可以由Spring容器处理，以便在运行时为这些Bean生成Bean定义和服务请求。