springboot 无法扫描到父类模块中Bean的原因及解决

目录 springboot 无法扫描到父类模块中Bean 现象： 如何解决 解决方案 spring boot 启动就自动关闭 之 找不到bean 解决方法： 原因： 以下收集别的解释： 所以有两种解决办法：

springboot 无法扫描到父类模块中Bean

现象：

我定义了两个模块 A 和 B 。B模块依赖A模块

A模块中我定义了一个@Component

却发现在B模块中我无法扫描到这个Bean导入注入失败

如何解决

查阅得知，在springboot中的bean扫描是扫描同级目录或者下级目录，也就是不会扫描到依赖包里面的东西。

但是我又想定义公共Bean，该怎么做呢。

解决方案

手动注入 @Bean

如果你定义的是实体类之类的Bean，那么可以在子类中手动Bean

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@Bean Result result(){   new Result; }

配置扫描 @ComponentScan

但是如果你定义的Bean是类似于接口的文件，那你使用手动定义的方法就会发现要写很长一段，把所有的方法都定义一下。所以还有另一种方法

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@SpringBootApplication @ComponentScan (basePackages = { "cn.o" }) public class ProxyDataSourceApplication {   ...main(){   } }

如果定义了@ComponentScan扫描路径，注意不要让@Bean多处定义，否则会报重复注入的错误。

spring boot 启动就自动关闭 之 找不到bean

创建的bean

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package com.springboot.entity; import org.springframework.boot.context.properties.ConfigurationProperties; import org.springframework.context.annotation.ComponentScan; import org.springframework.stereotype.Component;   /**   * Created by ASUS on 2018/3/20.   */ @Component @ConfigurationProperties (prefix = "author" ) public class AuthorBean {      private String name;      private Long age;        public void setName(String name) {          this .name = name;      }        public String getName() {          return name;      }        public void setAge(Long age) {          this .age = age;      }        public Long getAge() {          return age;      } }

写的application类

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package com.springboot.demo; import com.springboot.entity.AuthorBean; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.boot.SpringApplication; import org.springframework.context.annotation.ComponentScan; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController;   /**   * Created by ASUS on 2018/3/20.   */ @RestController @org .springframework.boot.autoconfigure.SpringBootApplication   public class ApplicationDemo {      @Autowired      private AuthorBean authorBean;        @RequestMapping ( "/kkk" )      String index(){          return "author name =" +authorBean.getName()+ "author age=" +authorBean.getAge();      }        public static void main(String[] args) {          SpringApplication.run(ApplicationDemo. class ,args);      } }

控制台报错：

2018-03-20 22:22:02.070 INFO 11360 --- [ main] com.springboot.demo.ApplicationDemo : Starting ApplicationDemo on DESKTOP-IV2AEJK with PID 11360 (D:\IDEA\IDEAWorkSpace\SpringBootDemo\target\classes started by ASUS in D:\IDEA\IDEAWorkSpace\SpringBootDemo)
2018-03-20 22:22:02.074 INFO 11360 --- [ main] com.springboot.demo.ApplicationDemo : No active profile set, falling back to default profiles: default
2018-03-20 22:22:02.144 INFO 11360 --- [ main] ationConfigEmbeddedWebApplicationContext : Refreshing org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@3fa980b: startup date [Tue Mar 20 22:22:02 CST 2018]; root of context hierarchy
2018-03-20 22:22:03.453 INFO 11360 --- [ main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat initialized with port(s): 9090 (http)
2018-03-20 22:22:03.462 INFO 11360 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat]
2018-03-20 22:22:03.463 INFO 11360 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet Engine: Apache Tomcat/8.5.27
2018-03-20 22:22:03.557 INFO 11360 --- [ost-startStop-1] o.a.c.c.C.[.[localhost].[/helloboot] : Initializing Spring embedded WebApplicationContext
2018-03-20 22:22:03.558 INFO 11360 --- [ost-startStop-1] o.s.web.context.ContextLoader : Root WebApplicationContext: initialization completed in 1416 ms
2018-03-20 22:22:03.704 INFO 11360 --- [ost-startStop-1] o.s.b.w.servlet.ServletRegistrationBean : Mapping servlet: 'dispatcherServlet' to [/]
2018-03-20 22:22:03.707 INFO 11360 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean : Mapping filter: 'characterEncodingFilter' to: [/*]
2018-03-20 22:22:03.707 INFO 11360 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean : Mapping filter: 'hiddenHttpMethodFilter' to: [/*]
2018-03-20 22:22:03.707 INFO 11360 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean : Mapping filter: 'httpPutFormContentFilter' to: [/*]
2018-03-20 22:22:03.708 INFO 11360 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean : Mapping filter: 'requestContextFilter' to: [/*]
2018-03-20 22:22:03.741 WARN 11360 --- [ main] ationConfigEmbeddedWebApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'applicationDemo': Unsatisfied dependency expressed through field 'authorBean'; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'com.springboot.entity.AuthorBean' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
2018-03-20 22:22:03.742 INFO 11360 --- [ main] o.apache.catalina.core.StandardService : Stopping service [Tomcat]
2018-03-20 22:22:03.761 INFO 11360 --- [ main] utoConfigurationReportLoggingInitializer :

Error starting ApplicationContext. To display the auto-configuration report re-run your application with 'debug' enabled.
2018-03-20 22:22:03.858 ERROR 11360 --- [ main] o.s.b.d.LoggingFailureAnalysisReporter :

***************************
APPLICATION FAILED TO START
***************************
Description:
Field authorBean in com.springboot.demo.ApplicationDemo required a bean of type 'com.springboot.entity.AuthorBean' that could not be found.
Action:
Consider defining a bean of type 'com.springboot.entity.AuthorBean' in your configuration.
Process finished with exit code 1

其中：

意思就是找不到bean，没有注入进去。

解决方法：

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@RestController @org .springframework.boot.autoconfigure.SpringBootApplication @ComponentScan (basePackages = { "com.springboot.entity" }) public class ApplicationDemo {      @Autowired      private AuthorBean authorBean;

加注解

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1	@ComponentScan (basePackages = { "com.springboot.entity" })

原因：

@SpringBootApplication 注解组合了@Configuration @EnableAutoConfiguration，@ComponentScan.

spring boot 会自动扫描@SpringBootApplication 所在类的同级包以及下级包里的Bean ，建议入口类放置在groupid+arctifactId 组合的包名下

以下收集别的解释：

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

所以有两种解决办法：

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。

以上为个人经验，希望能给大家一个参考，也希望大家多多支持。

原文链接：https://blog.csdn.net/tutian2000/article/details/108508572

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