Java org.springframework.beans.factory.UnsatisfiedDependencyException：创建名为“demoRestController”的 bean 时出错

org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'demoRestController'

提问by Brain

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.

我是 Spring 的新手，我正在尝试制作一个学习应用程序，但是我在自动装配中遇到了问题，我正在添加我的代码。我正在研究弹簧靴。

Spring Boot Code

春季启动代码

public class DemoApplication {

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

LoginBean.java

登录Bean.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;
    }

I tried following scenarios to make my @Autowired work:

我尝试了以下场景来使我的 @Autowired 工作：

1. @Autowired to LoginBean loginBean;
2. Created getter setter of LoginBean in Controller class and autowired setters;
3. Created constructor of Controller and autowired, as given in above code;

1. @Autowired 到 LoginBean loginBean;
2. 在 Controller 类中创建了 LoginBean 的 getter setter 和自动装配的 setter；
3. 创建控制器的构造函数并自动装配，如上面的代码所示；

Below is the error which I am getting

下面是我得到的错误

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.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

采纳答案by Andy Wilkinson

Your DemoApplicationclass is in the com.ag.digital.demo.bootpackage and your LoginBeanclass is in the com.ag.digital.demo.beanpackage. 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 LoginBeanisn't being found so dependency injection fails.

你的DemoApplication班级在com.ag.digital.demo.boot包里，你的LoginBean班级在com.ag.digital.demo.bean包里。默认情况下，如果组件（用 注释的类@Component）位于主应用程序类的同一个包或子包中，则会找到它们DemoApplication。这意味着LoginBean没有找到，所以依赖注入失败。

There are a couple of ways to solve your problem:

有几种方法可以解决您的问题：

1. Move LoginBeaninto com.ag.digital.demo.bootor a sub-package.
2. Configure the packages that are scanned for components using the scanBasePackagesattribute of @SpringBootApplicationthat should be on DemoApplication.

1. 移动LoginBean到com.ag.digital.demo.boot或子包。
2. 使用应为 on的scanBasePackages属性配置扫描组件的包。@SpringBootApplicationDemoApplication

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

其他一些不会导致问题但与您发布的代码不太正确的事情：

• @Serviceis a specialisation of @Componentso you don't need both on LoginBean
• Similarly, @RestControlleris a specialisation of @Componentso you don't need both on DemoRestController
• DemoRestControlleris an unusual place for @EnableAutoConfiguration. That annotation is typically found on your main application class (DemoApplication) either directly or via @SpringBootApplicationwhich is a combination of @ComponentScan, @Configuration, and @EnableAutoConfiguration.

• @Service是一个专业，@Component所以你不需要两者都LoginBean
• 同样，@RestController是一个专业，@Component所以你不需要两者都在DemoRestController
• DemoRestController是一个不寻常的地方@EnableAutoConfiguration。该注释在您的主应用程序类通常发现（DemoApplication）直接或经由@SpringBootApplication其的组合@ComponentScan，@Configuration和@EnableAutoConfiguration。