org.springframework.beans.factory.UnsatisfiedDependencyException：创建名称为'demoRestController'的bean时出错 [英] org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'demoRestController'

问题描述

我是Spring的新手，我尝试制作一个学习应用程序，但是在自动装配中遇到了问题，正在添加代码。我正在使用Spring Boot。

I am new to Spring and I am try to make a application for learning but I am getting problem in Autowiring,I am adding my code. I am working on spring boot.

Spring Boot代码

Spring Boot Code

public class DemoApplication {

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

LoginBean.java

LoginBean.java

@Service
@Component
public class LoginBean {
    private String userId;
    private String pwd;

    public String getUserId() {
        return userId;
    }

    public void setUserId(String userId) {
        this.userId = userId;
    }

    public String getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }

DemoRestController.java

DemoRestController.java

@RestController
@EnableAutoConfiguration
@RequestMapping("/demo")
@Component
public class DemoRestController {


    private final LoginBean loginBean;

    @Autowired
    public DemoRestController(LoginBean loginBean) {
        this.loginBean=loginBean;
    }

    @RequestMapping(value = "/login/{id},{pwd}", method = RequestMethod.GET, produces = "application/json")
    public @ResponseBody LoginBean loginService(@PathVariable String id, @PathVariable String pwd) {
        //LoginBean loginBean = new LoginBean();

        loginBean.setUserId(id);
        loginBean.setPwd(pwd);
        return loginBean;
    }

我尝试了以下几种方案来制作@Autowired作品：

I tried following scenarios to make my @Autowired work:

1. @Autowired到LoginBean loginBean;


2. 在Controller类和自动装配的设置器中创建LoginBean的getter设置器；


3. 创建Controller的构造函数并自动装配，如上面的代码所示；

以下是我得到的错误

org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'demoRestController': Unsatisfied dependency expressed through constructor argument with index 0 of type [com.ag.digital.demo.bean.LoginBean]: No qualifying bean of type [com.ag.digital.demo.bean.LoginBean] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {}; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [com.ag.digital.demo.bean.LoginBean] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {}
    at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:749) ~[spring-beans-4.2.5.RELEASE.jar:4.2.5.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:185) ~[spring-beans-4.2.5.RELEASE.jar:4.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:1143) ~[spring-beans-4.2.5.RELEASE.jar:4.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1046) ~[spring-beans-4.2.5.RELEASE.jar:4.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:510) ~[spring-beans-4.2.5.RELEASE.jar:4.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:482) ~[spring-beans-4.2.5.RELEASE.jar:4.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306) ~[spring-beans-4.2.5.RELEASE.jar:4.2.5.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) ~[spring-beans-4.2.5.RELEASE.jar:4.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302) ~[spring-beans-4.2.5.RELEASE.jar:4.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197) ~[spring-beans-4.2.5.RELEASE.jar:4.2.5.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:772) ~[spring-beans-4.2.5.RELEASE.jar:4.2.5.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:839) ~[spring-context-4.2.6.RELEASE.jar:4.2.6.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:538) ~[spring-context-4.2.6.RELEASE.jar:4.2.6.RELEASE]
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:118) ~[spring-boot-1.3.3.RELEASE.jar:1.3.3.RELEASE]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:766) [spring-boot-1.3.3.RELEASE.jar:1.3.3.RELEASE]
    at org.springframework.boot.SpringApplication.createAndRefreshContext(SpringApplication.java:361) [spring-boot-1.3.3.RELEASE.jar:1.3.3.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:307) [spring-boot-1.3.3.RELEASE.jar:1.3.3.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1191) [spring-boot-1.3.3.RELEASE.jar:1.3.3.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1180) [spring-boot-1.3.3.RELEASE.jar:1.3.3.RELEASE]
    at com.ag.digital.demo.boot.DemoApplication.main(DemoApplication.java:14) [classes/:na]
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [com.ag.digital.demo.bean.LoginBean] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {}
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoSuchBeanDefinitionException(DefaultListableBeanFactory.java:1373) ~[spring-beans-4.2.5.RELEASE.jar:4.2.5.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1119) ~[spring-beans-4.2.5.RELEASE.jar:4.2.5.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1014) ~[spring-beans-4.2.5.RELEASE.jar:4.2.5.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.resolveAutowiredArgument(ConstructorResolver.java:813) ~[spring-beans-4.2.5.RELEASE.jar:4.2.5.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:741) ~[spring-beans-4.2.5.RELEASE.jar:4.2.5.RELEASE]
    ... 19 common frames omitted

推荐答案

您的 DemoApplication 类位于 com.ag.digital.demo.boot 包，您的 LoginBean 类位于 com.ag中。 digital.demo.bean 软件包。默认情况下，如果组件（使用 @Component 注释的类）位于主应用程序类 DemoApplication <的同一包或子包中，则将找到它们。 / code>。这意味着未找到 LoginBean ，因此依赖项注入失败。

Your DemoApplication class is in the com.ag.digital.demo.boot package and your LoginBean class is in the com.ag.digital.demo.bean package. By default components (classes annotated with @Component) are found if they are in the same package or a sub-package of your main application class DemoApplication. This means that LoginBean isn't being found so dependency injection fails.

有两种解决方法您的问题：

There are a couple of ways to solve your problem:

1. 将 LoginBean 移至 com.ag .digital.demo.boot 或子软件包。


2. 配置使用 scanBasePackages @SpringBootApplication 的c $ c>属性应该在 DemoApplication 上。

1. Move LoginBean into com.ag.digital.demo.boot or a sub-package.
2. Configure the packages that are scanned for components using the scanBasePackages attribute of @SpringBootApplication that should be on DemoApplication.

其他一些不会引起问题的东西，但与您发布的代码不太相符：

A few of other things that aren't causing a problem, but are not quite right with the code you've posted:

• @Service 是 @Component 的特化，所以您不必同时需要 LoginBean


• 类似地， @RestController 是 @Component ，因此您不需要在 DemoRestController
上同时使用

• DemoRestController 对于 @E是一个不寻常的地方nableAutoConfiguration 。通常可以直接在主应用程序类（ DemoApplication ）上找到注释，也可以通过 @SpringBootApplication 找到该注释 @ComponentScan ， @Configuration 和 @EnableAutoConfiguration 。 / li>
  

• @Service is a specialisation of @Component so you don't need both on LoginBean
• Similarly, @RestController is a specialisation of @Component so you don't need both on DemoRestController
• DemoRestController is an unusual place for @EnableAutoConfiguration. That annotation is typically found on your main application class (DemoApplication) either directly or via @SpringBootApplication which is a combination of @ComponentScan, @Configuration, and @EnableAutoConfiguration.

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