我是 Spring 的新手,我正在尝试制作一个学习应用程序,但我在 Autowiring 中遇到问题,我正在添加我的代码。我正在研究 spring boot。
Spring 启动代码
public class DemoApplication {
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
}
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
@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;
}
我尝试了以下场景来使我的@Autowired 工作:
- @Autowired 到 LoginBean loginBean;
- 在 Controller 类中创建 LoginBean 的 getter setter 和 Autowiring 的 setter;
- 创建 Controller 的构造函数并 Autowiring ,如上面的代码所示;
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$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
最佳答案
您的 DemoApplication
类在 com.ag.digital.demo.boot
包中,您的 LoginBean
类在 com.ag.digital.demo.bean
包。默认情况下,如果组件(用 @Component
注释的类)位于主应用程序类 DemoApplication
的同一个包或子包中,则会被找到。这意味着未找到 LoginBean
,因此依赖注入(inject)失败。
有几种方法可以解决您的问题:
- 将
LoginBean
移动到com.ag.digital.demo.boot
或子包中。 - 使用
@SpringBootApplication
的scanBasePackages
属性配置扫描组件的包,该属性应该在DemoApplication
上。
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:
@Service
是@Component
的特化,因此您不需要LoginBean
- 同样,
@RestController
是@Component
的特化,因此您不需要在DemoRestController
上同时使用它们
DemoRestController
是@EnableAutoConfiguration
的一个不寻常的地方。该注解通常可以在您的主应用程序类 (DemoApplication
) 上直接找到,也可以通过@SpringBootApplication
找到,它是@ComponentScan
、的组合>@Configuration
和@EnableAutoConfiguration
。
关于java - org.springframework.beans.factory.UnsatisfiedDependencyException : Error creating bean with name 'demoRestController' ,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/37214538/