@Autowired 在 Spring Boot 中的 @Controller 中不起作用

Question

当我尝试在 Controller 中自动连接我的存储库时出现错误。 我已经看到其他人的这个问题，但没有一个解决方案对我有用。

org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'com.example.test.app.repo.TestRepo' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {}
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoMatchingBeanFound(DefaultListableBeanFactory.java:1801) ~[spring-beans-5.3.21.jar:5.3.21]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1357) ~[spring-beans-5.3.21.jar:5.3.21]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1311) ~[spring-beans-5.3.21.jar:5.3.21]
    at org.springframework.beans.factory.support.ConstructorResolver.resolveAutowiredArgument(ConstructorResolver.java:887) ~[spring-beans-5.3.21.jar:5.3.21]
    at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:791) ~[spring-beans-5.3.21.jar:5.3.21]
    at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:229) ~[spring-beans-5.3.21.jar:5.3.21]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:1372) ~[spring-beans-5.3.21.jar:5.3.21]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1222) ~[spring-beans-5.3.21.jar:5.3.21]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:582) ~[spring-beans-5.3.21.jar:5.3.21]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:542) ~[spring-beans-5.3.21.jar:5.3.21]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:335) ~[spring-beans-5.3.21.jar:5.3.21]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234) ~[spring-beans-5.3.21.jar:5.3.21]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:333) ~[spring-beans-5.3.21.jar:5.3.21]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:208) ~[spring-beans-5.3.21.jar:5.3.21]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:955) ~[spring-beans-5.3.21.jar:5.3.21]
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:918) ~[spring-context-5.3.21.jar:5.3.21]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:583) ~[spring-context-5.3.21.jar:5.3.21]
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:147) ~[spring-boot-2.7.1.jar:2.7.1]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:734) ~[spring-boot-2.7.1.jar:2.7.1]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:408) ~[spring-boot-2.7.1.jar:2.7.1]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:308) ~[spring-boot-2.7.1.jar:2.7.1]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1306) ~[spring-boot-2.7.1.jar:2.7.1]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1295) ~[spring-boot-2.7.1.jar:2.7.1]
    at com.example.test.app.MainApplication.main(MainApplication.java:12) ~[classes/:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
    at java.base/java.lang.reflect.Method.invoke(Method.java:564) ~[na:na]
    at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49) ~[spring-boot-devtools-2.7.1.jar:2.7.1]

2022-07-21 17:40:25.777 ERROR 5616 --- [  restartedMain] o.s.b.d.LoggingFailureAnalysisReporter   : 

***************************
APPLICATION FAILED TO START
***************************

Description:

Parameter 0 of constructor in com.example.test.app.controller.TestController required a bean of type 'com.example.test.app.repo.TestRepo' that could not be found.


Action:

Consider defining a bean of type 'com.example.test.app.repo.TestRepo' in your configuration.


Process finished with exit code 0

我的项目结构

聚甲醛：

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.7.1</version>
        <relativePath/>
    </parent>
    <groupId>com.example</groupId>
    <artifactId>test</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>test</name>
    <description>test</description>
    <properties>
        <java.version>11</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
            <exclusions>
                <exclusion>
                    <groupId>com.zaxxer</groupId>
                    <artifactId>HikariCP</artifactId>
                </exclusion>
            </exclusions>
        </dependency>

        <dependency>
            <groupId>org.postgresql</groupId>
            <artifactId>postgresql</artifactId>
            <scope>runtime</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

主应用类：

@SpringBootApplication
public class MainApplication{

    public static void main(String[] args) {
        SpringApplication.run(MainApplication.class, args);
    }

}

存储库：

@Repository
public interface TestRepo extends CrudRepository<Person, Long> {
    Person findById(long id);
}

控制器：

@Controller
@RequestMapping("/greet")
public class TestController {
    private TestRepo testRepo;
    @Autowired
    public TestController(TestRepo testRepo) {
        this.testRepo = testRepo;
    }

    @GetMapping
    public String greet() {
        return "home";
    }
}

人：

@Entity
public class Person {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    private String name;

    public Person() {
    }

    public Person(String name) {
        this.name = name;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public Long getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

我试图在 MainApplication 类中添加@ComponentScan("com.example.test.app.repo")注释。 应用程序启动时没有错误，但映射不起作用，我看到 Whitelabel 错误页面并在日志中得到这个：

2022-07-21 17:37:03.789 DEBUG 8152 --- [nio-8081-exec-4] o.s.web.servlet.DispatcherServlet        : GET "/greet", parameters={}
2022-07-21 17:37:03.790 DEBUG 8152 --- [nio-8081-exec-4] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped to ResourceHttpRequestHandler [classpath [META-INF/resources/], classpath [resources/], classpath [static/], classpath [public/], ServletContext [/]]
2022-07-21 17:37:03.802 DEBUG 8152 --- [nio-8081-exec-4] o.s.w.s.r.ResourceHttpRequestHandler     : Resource not found
2022-07-21 17:37:03.802 DEBUG 8152 --- [nio-8081-exec-4] o.s.web.servlet.DispatcherServlet        : Completed 404 NOT_FOUND
2022-07-21 17:37:03.802 DEBUG 8152 --- [nio-8081-exec-4] o.s.web.servlet.DispatcherServlet        : "ERROR" dispatch for GET "/error", parameters={}
2022-07-21 17:37:03.803 DEBUG 8152 --- [nio-8081-exec-4] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped to org.springframework.boot.autoconfigure.web.servlet.error.BasicErrorController#errorHtml(HttpServletRequest, HttpServletResponse)
2022-07-21 17:37:03.817 DEBUG 8152 --- [nio-8081-exec-4] o.s.w.s.v.ContentNegotiatingViewResolver : Selected 'text/html' given [text/html, text/html;q=0.8]
2022-07-21 17:37:03.818 DEBUG 8152 --- [nio-8081-exec-4] o.s.web.servlet.DispatcherServlet        : Exiting from "ERROR" dispatch, status 404

还尝试将 MainApplication 移动到自己的包中。 错误也消失了，但映射也不起作用。 @Qualifier也没有帮助

Answer 1

在我看来，您已将HikariCP从您的spring-boot-starter-data-jpa中排除。 这意味着，在进行扫描时，spring 将尝试获取CrudRepository的类的实现，这些类没有任何对HikariCP的依赖。

您可以尝试在您的application.properties或application.yml中配置您的存储库，然后检查您是否能够正确运行应用程序。

如果您已经配置了属性，请分享它，以便根据配置更新答案。