Spring Boot Annotation @Autowired of Service失败 [英] Spring Boot Annotation @Autowired of Service fails

问题描述

我试图在Spring Boot应用程序的Service类中使用@Autowired批注，但是它总是抛出No qualifying bean of type异常.但是，如果我将服务类更改为Bean，则可以正常工作.这是我的代码:

I'm trying to use @Autowired annotation for a Service class in Spring Boot application, but it keeps throwing No qualifying bean of type exception. However, if I change the service class to a bean, then it works fine. This is my code:

package com.mypkg.domain;
@Service
public class GlobalPropertiesLoader {

    @Autowired
    private SampleService sampleService;        
}

package com.mypkg.service;
@Service
public class SampleService{

}

这是我的SpringBoot类:

And this is my SpringBoot class:

package com.mypkg;

import java.util.Set;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.data.rest.webmvc.config.RepositoryRestMvcConfiguration;
import org.springframework.transaction.annotation.EnableTransactionManagement;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.ClassPathScanningCandidateComponentProvider;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Import;

@SpringBootApplication
@EnableJpaRepositories
@Import(RepositoryRestMvcConfiguration.class)
@EnableTransactionManagement
public class TrackingService {
    private static final Logger LOGGER = LoggerFactory.getLogger(TrackingService.class);

    static AnnotationConfigApplicationContext context;

    public static void main(String[] args) throws Exception {
        SpringApplication.run(TrackingService.class, args);
        context = new AnnotationConfigApplicationContext();
        context.refresh();
        context.close();

    }

}

当我尝试运行此命令时，出现以下异常:

When I try to run this, I get the following exception:

Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [com.mypkg.service.SampleService] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}

但是当我从SampleService类中删除@Service批注，并将其作为bean添加到我的AppConfig类中时，如下所示，它可以正常工作:

But when I remove the @Service annotation from the SampleService class, and add it as a bean in my AppConfig class as below, it works fine:

@Configuration
public class AppServiceConfig {

    public AppServiceConfig() {
    }

    @Bean(name="sampleService")
    public SampleService sampleService(){
        return new SampleService();
    }

}

这些类位于不同的程序包中.我没有使用@ComponentScan.相反，我使用的是@SpringBootApplication，它会自动执行此操作.但是，我也尝试了ComponentScan，但这没有帮助.

The classes are in different packages. I am not using @ComponentScan. Instead, I'm using @SpringBootApplication which does that automatically. However, I tried with ComponentScan as well but that didn't help.

我在做什么错了?

推荐答案

您正在使用两种方法来构建Spring的bean.您只需要使用其中之一即可.

You are using two ways to build a Spring's bean. You just need to use one of them.

1. @Service在POJO上

 @Service
 public class SampleService

配置类中的

@Bean，必须用@Configuration

@Bean in the configuration class which must be annotated with @Configuration

 @Bean
 public SampleService sampleService(){
     return new SampleService();
 }

@Autowired由类类型解析，则不需要@Bean(name="sampleService")，因为您只有一个具有该类类型的bean.

@Autowired is resolved by class type then @Bean(name="sampleService") is not needed is you have only one bean with that class type.

编辑01

打包com.example

package com.example

@SpringBootApplication
public class Application implements CommandLineRunner {

    public static void main(String... args) {
        SpringApplication.run(Application.class);
    }

    @Autowired
    private UserRepository userRepository;

    @Autowired
    private UserService userService;

    @Override
    public void run(String... strings) throws Exception {
        System.out.println("repo " + userRepository);
        System.out.println("serv " + userService);
    }
}

打包com.example.config

package com.example.config

@Configuration
public class AppConfig {

    @Bean
    public UserRepository userRepository() {
        System.out.println("repo from bean");
        return new UserRepository();
    }

    @Bean
    public UserService userService() {
        System.out.println("ser from bean");
        return new UserService();
    }
}

打包com.example.repository

package com.example.repository

@Service
public class UserRepository {

    @PostConstruct
    public void init() {
        System.out.println("repo from @service");
    }
}

打包com.example.service

package com.example.service

@Service
public class UserService {

    @PostConstruct
    public void init() {
        System.out.println("service from @service");
    }

}

使用此代码，您可以注释AppConfig类，然后您将看到如何自动连接UserRepository和UserService.在每个类中添加注释@Service之后，取消注释AppConfig和类也将自动连接.

Using this code you can comment the AppConfig class and then you will see how UserRepository and UserService are autowired. After that comment @Service in each class and un-comment AppConfig and classes will be autowired too.

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