Description:
Field demoService in com.spring.web.DemoApplication required a bean of type 'com.spring.service.DemoService' that could not be found.
Action:
Consider defining a bean of type 'com.spring.service.DemoService' in your configuration.
Service:DemoService
报错:
解决办法:
Field demoService in com.spring.web.DemoApplication required a bean of type 'com.spring.service.DemoService' that could not be found.
Action:
Consider defining a bean of type 'com.spring.service.DemoService' in your configuration.
谷歌翻译为:
com.spring.web.DemoApplication中的field demoService需要无法找到类型为“com.spring.service.DemoService”的bean。
我的代码:
controller:DemoApplication
package com.spring.web; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.EnableAutoConfiguration; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration; import org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; import com.spring.service.DemoService; @RestController //@EnableAutoConfiguration @SpringBootApplication() public class DemoApplication { @Autowired private DemoService demoService; @RequestMapping("/") public String helloWorld(){ String msg = demoService.demo(); return msg; } public static void main(String[] args) { SpringApplication.run(DemoApplication.class, args); } }
Service:DemoService
package com.spring.service; public interface DemoService { public String demo(); }
ServiceImpl:DemoServiceImpl
package com.spring.service.impl; import org.springframework.stereotype.Service; import com.spring.service.DemoService; @Component public class DemoServiceImpl implements DemoService { @Override public String demo() { System.out.println("Hello World!"); return "Hello World!"; } }
报错:
. ____ _ __ _ _ /\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \ ( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \ \\/ ___)| |_)| | | | | || (_| | ) ) ) ) ' |____| .__|_| |_|_| |_\__, | / / / / =========|_|==============|___/=/_/_/_/ :: Spring Boot :: (v1.5.6.RELEASE) 2017-09-11 16:16:10.367 INFO 14512 --- [ main] com.spring.web.DemoApplication : Starting DemoApplication on PC2014101864 with PID 14512 (E:\workspacedubbo\boot\boot-web\target\classes started by Administrator in E:\workspacedubbo\boot\boot-web) 2017-09-11 16:16:10.369 INFO 14512 --- [ main] com.spring.web.DemoApplication : No active profile set, falling back to default profiles: default 2017-09-11 16:16:10.421 INFO 14512 --- [ main] ationConfigEmbeddedWebApplicationContext : Refreshing org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@31206beb: startup date [Mon Sep 11 16:16:10 CST 2017]; root of context hierarchy 2017-09-11 16:16:11.710 INFO 14512 --- [ main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat initialized with port(s): 8080 (http) 2017-09-11 16:16:11.721 INFO 14512 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat] 2017-09-11 16:16:11.722 INFO 14512 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet Engine: Apache Tomcat/8.5.16 2017-09-11 16:16:11.856 INFO 14512 --- [ost-startStop-1] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext 2017-09-11 16:16:11.856 INFO 14512 --- [ost-startStop-1] o.s.web.context.ContextLoader : Root WebApplicationContext: initialization completed in 1438 ms 2017-09-11 16:16:11.992 INFO 14512 --- [ost-startStop-1] o.s.b.w.servlet.ServletRegistrationBean : Mapping servlet: 'dispatcherServlet' to [/] 2017-09-11 16:16:11.995 INFO 14512 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean : Mapping filter: 'characterEncodingFilter' to: [/*] 2017-09-11 16:16:11.995 INFO 14512 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean : Mapping filter: 'hiddenHttpMethodFilter' to: [/*] 2017-09-11 16:16:11.995 INFO 14512 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean : Mapping filter: 'httpPutFormContentFilter' to: [/*] 2017-09-11 16:16:11.995 INFO 14512 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean : Mapping filter: 'requestContextFilter' to: [/*] 2017-09-11 16:16:12.025 WARN 14512 --- [ main] ationConfigEmbeddedWebApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'demoApplication': Unsatisfied dependency expressed through field 'demoService'; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'com.spring.service.DemoService' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)} 2017-09-11 16:16:12.026 INFO 14512 --- [ main] o.apache.catalina.core.StandardService : Stopping service [Tomcat] 2017-09-11 16:16:12.038 INFO 14512 --- [ main] utoConfigurationReportLoggingInitializer : Error starting ApplicationContext. To display the auto-configuration report re-run your application with 'debug' enabled. 2017-09-11 16:16:12.107 ERROR 14512 --- [ main] o.s.b.d.LoggingFailureAnalysisReporter : *************************** APPLICATION FAILED TO START *************************** Description: Field demoService in com.spring.web.DemoApplication required a bean of type 'com.spring.service.DemoService' that could not be found. Action: Consider defining a bean of type 'com.spring.service.DemoService' in your configuration.
解决办法:
根据英文的提示是在配置中找不到一个指定自动注入类型的bean,
网上搜索得知,
SpringBoot项目的Bean装配默认规则是根据Application类所在的包位置从上往下扫描!
“Application类”是指SpringBoot项目入口类。这个类的位置很关键:
如果Application类所在的包为:com.boot.app,则只会扫描com.boot.app包及其所有子包,如果service或dao所在包不在com.boot.app及其子包下,则不会被扫描!
即, 把Application类放到dao、service所在包的上级,com.boot.Application
知道这一点非常关键,不知道Spring文档里有没有给出说明,如果不知道还真是无从解决。
经过多方排查得出结论:
正常情况下加上@Component注解的类会自动被Spring扫描到生成Bean注册到spring容器中,既然他说没找到,也就是该注解被没有被spring识别,问题的核心关键就在application类的注解SpringBootApplication上,
正常情况下加上@Component注解的类会自动被Spring扫描到生成Bean注册到spring容器中,既然他说没找到,也就是该注解被没有被spring识别,问题的核心关键就在application类的注解SpringBootApplication上,
这个注解其实相当于下面这一堆注解的效果,其中一个注解就是@Component,在默认情况下只能扫描与控制器在同一个包下以及其子包下的@Component注解,以及能将指定注解的类自动注册为Bean的@Service@Controller和@ Repository,至此明白问题所在,之前我将接口与对应实现类放在了与控制器所在包的同一级目录下,这样的注解自然是无法被识别的。
之前我的controller和service是在同级目录下面现把controller放在service的上级目录,再启动就不报错了。
至此,得出两种解决办法:
1 .将接口与对应的实现类放在与application启动类的同一个目录或者他的子目录下,这样注解可以被扫描到,这是最省事的办法
2 .在指定的application类上加上这么一行注解,手动指定application类要扫描哪些包下的注解,见下图