Spring Boot 調用 MongoRepository時報org.springframework.beans.factory.NoSuchBeanDefinitionException錯誤的解決辦法

這個問題整整折騰了我兩天，現在記錄下來，希望可以幫助和我一樣，遇到相同問題的小伙伴。

項目是分層的（Intellij IDEA中的模塊Module），有API（Core）層，Service&Dao，Common，Model，上一張項目結構圖。（不要在意為什么Service和Dao放在一起。這不是重點。）

API中包括了Controller，Mongodb在Service&Dao層中，也就是API層，調用Service&Dao層，我敢用性命擔保，所有注釋，邏輯，都沒有錯，但是運行SpringBoot的時候，偏偏報錯。（找不到依賴，就是注入失敗。）

代碼中繼承了MongoRepository接口

public interface IUserGroupRepository extends MongoRepository<UserGroup, Integer> {
    UserGroup findById(Integer id);
}

　報錯內容如下：

2017-06-28 10:11:52.423  WARN 8648 --- [           main] ationConfigEmbeddedWebApplicationContext : Exception encountered during context initialization - cancelling refresh attempt:
 org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'userGroupController': Unsatisfied dependency expressed through field 'userGroupRepository'; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'com.iboxpay.nosql.mongodb.IUserGroupRepository' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
2017-06-28 10:11:52.426  INFO 8648 --- [           main] o.apache.catalina.core.StandardService   : Stopping service [Tomcat]
2017-06-28 10:11:52.446  INFO 8648 --- [           main] utoConfigurationReportLoggingInitializer : 

Error starting ApplicationContext. To display the auto-configuration report re-run your application with 'debug' enabled.
2017-06-28 10:11:52.591 ERROR 8648 --- [           main] o.s.b.d.LoggingFailureAnalysisReporter   : 

***************************
APPLICATION FAILED TO START
***************************

Description:

Field userGroupRepository in com.iboxpay.ops.api.controller.UserGroupController required a bean of type 'com.iboxpay.nosql.mongodb.IUserGroupRepository' that could not be found.


Action:

Consider defining a bean of type 'com.iboxpay.nosql.mongodb.IUserGroupRepository' in your configuration.

　　解決辦法如下：

@SpringBootApplication(scanBasePackages = {"com.iboxpay.service", "com.iboxpay.ops.api", "com.iboxpay.nosql"})
@EnableMongoRepositories(basePackages = {"com.iboxpay.nosql"})
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

因為我的項目是分層的，SpringBoot的@SpringBootApplication注解要添加掃描包，否則有的地方可能會注入失敗。另外一點比較重要，需要使有和Mongodb的@EnableMongoRepositories注解，並指定要掃描的包（IUserGroupRepository所在的包，即繼承

MongoRepository接口的接口中所在的包。）
上面兩個com.iboxpay.nosql缺一不可。切記，切記。