通过字段“userRepository”表达的不满足的依赖关系

Question

无法解决测试 Spring Boot 应用程序的问题：

spring.bat init --artifactId=dbproto3 --boot-version=2.1.7.RELEASE --dependencies=jdbc,data-rest,web,thymeleaf,devtools,lombok,configuration-processor,security,data-jpa,data-jdbc,postgresql,actuator --description=dbproto3 --groupId=com.test --java-version=11 --name=dbproto3 --package-name=com.test.dbproto3 --version=0.0.1-SNAPSHOT

这是一个测试应用程序，通过修改Spring官方网站的Guide "Accessing data with MySQL"。第一个版本（接近初始版本：空 springconfig、@Controller 和 @RequestMapping(path="/demo")，...）效果很好，但我的版本会产生异常

运行它我得到一个异常：

Exception in thread "restartedMain" java.lang.reflect.InvocationTargetException
  2 .   at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  3 .   at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
  4 .   at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
  5 .   at java.base/java.lang.reflect.Method.invoke(Method.java:566)
  6 .   at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49)
  7 . Caused by: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'mainController': Unsatisfied dependency expressed through field 'userRepository'; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'com.test.dbproto3.UserRepository' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
  8 .   at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:596)
  9 .   at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:90)
 10 .   at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessProperties(AutowiredAnnotationBeanPostProcessor.java:374)
 11 .   at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1411)
 12 .   at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:592)
 13 .   at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:515)
 14 .   at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320)
 15 .   at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
 16 .   at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318)
 17 .   at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199)
 18 .   at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:845)
 19 .   at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:877)
 20 .   at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:549)
 21 .   at org.springframework.context.annotation.AnnotationConfigApplicationContext.<init>(AnnotationConfigApplicationContext.java:88)
 22 .   at com.test.dbproto3.Dbproto3Application.main(Dbproto3Application.java:18)
 23 .   ... 5 more
 24 . Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'com.test.dbproto3.UserRepository' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
 25 .   at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoMatchingBeanFound(DefaultListableBeanFactory.java:1658)
 26 .   at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1217)
 27 .   at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1171)
 28 .   at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:593)
 29 .   ... 19 more

Dbproto3Application：

@SpringBootApplication
  2 . public class Dbproto3Application {
  3 .
  4 .    public static void main(String[] args) {
  5 .         SpringApplication.run(Dbproto3Application.class, args);
  6 .
  7 .         ApplicationContext javaConfigContext = new AnnotationConfigApplicationContext(SpringConfig.class);
  8 .
  9 .         MainController mainControllerObj = (MainController) javaConfigContext.getBean("mainController");
 10 .
 11 .         mainControllerObj.addNewUser();
 12 .    }
 13 . }

SpringConfig：

  1 . @Configuration
  2 . public class SpringConfig {
  3 .     @Bean("mainController")
  4 .     public MainController createMainController() {
  5 .         return new MainController();
  6 .     }
  7 . }

用户：

 1 . @Entity
  2 . @Table(name = "userstab")
  3 . public class User {
  4 .   @Id
  5 .   @GeneratedValue(strategy=GenerationType.AUTO)
  6 .   private Integer id;
  7 .
  8 .   private String name;
  9 .
 10 .   private String email;
 11 .
 12 . }

用户存储库：

  1 . public interface UserRepository extends CrudRepository<User, Integer> {
  2 .
  3 . }

主控制器：

  3 . public class MainController {
  4 .
  5 .     @Autowired
  6 .     private UserRepository userRepository;
  7 .
  8 .
  9 .     public void addNewUser() {
 10 .         User n = new User();
 11 .         n.setName("testuser");
 12 .         n.setEmail("testemail");
 13 .         System.out.println("addNewUser()");
 14 .         userRepository.save(n);
 15 .     }
 16 .
 17 . }

应用程序属性：

server.port = 8082

## default connection pool
spring.datasource.hikari.connectionTimeout=20000
spring.datasource.hikari.maximumPoolSize=5


## PostgreSQL
spring.datasource.url=jdbc:postgresql://localhost:5432/example_db
spring.datasource.username=someuser
spring.datasource.password=123456

spring.jpa.hibernate.ddl-auto=update

Answer 1

在您共享的代码中，我看不到您的存储库接口的任何注释。即使您正在扩展CrudRepository 接口以创建自己的接口。 Spring boot 需要在启动期间了解它需要为您的实体提供默认实现。在您的界面上使用注释 @Repository，例如：

 @Repository
 public interface UserRepository extends CrudRepository<User, Integer> {
  
  }

另外，您正在以某种奇怪的方式创建控制器 bean，因此您可能正在尝试一些非常规的东西，这意味着在您的主应用程序类中使用 @Autowired 对您来说也可能有点牵强。但我建议这样做。您正在使用 AnnotationConfigApplicationContext 为您的控制器创建 bean，但您只提供了为扫描创建的配置类。也许 UserRepository 的 bean 因为它是由 springboot 创建的，所以在您使用 AnnotationConfigApplicationContext 创建的应用程序上下文中不存在。我认为这是一个独立的上下文。