Spring boot项目启动自动加载mongo配置失败导致启动失败问题
总结一下在一次spring boot 项目启动中遇到的问题，主要原因是启动时提示在加载dataSource defined in class path resource org/springframework/boot/autoconfigure/jdbc/DataSourceConfiguration$Hikari.class时失败。
该项目是一个网关项目，只配置了一个redis数据源，且最近一段时间未改动过任何配置（环境配置、pom均为改动）。所以突然出现启动失败，感觉很困惑！开始怀疑测试环境问题（测试环境使用的docker，不是很稳定）后来本地启动、预发环境启动master分支同样问题，排除docker环境因素！
仔细看日志，加载dataSource报连接mongodb失败，也就是spring boot在启动时去加载dataSource,然后从配置文件中去加载连接mongodb的配置没有找到，导致连接失败。
2020-04-10 09:47:47,567 [localhost-startStop-1] INFO org.springframework.web.context.ContextLoader - Root WebApplicationContext: initialization completed in 3576 ms
2020-04-10 09:47:48,107 [localhost-startStop-1] INFO org.mongodb.driver.cluster - Cluster created with settings {hosts=[localhost:27017], mode=SINGLE, requiredClusterType=UNKNOWN, serverSelectionTimeout='30000 ms', maxWaitQueueSize=500}
2020-04-10 09:47:48,129 [cluster-ClusterId{value='5e8fd0441919428f62237562', description='null'}-localhost:27017] INFO org.mongodb.driver.cluster com.mongodb.MongoSocketOpenException: Exception opening socket
at com.mongodb.connection.SocketStream.open(SocketStream.java:62)
at com.mongodb.connection.InternalStreamConnection.open(InternalStreamConnection.java:126)
at com.mongodb.connection.DefaultServerMonitor$ServerMonitorRunnable.run(DefaultServerMonitor.java:114)
at java.lang.Thread.run(Thread.java:748)
Caused by: java.net.ConnectException: Connection refused (Connection refused)
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:589)
at com.mongodb.connection.SocketStreamHelper.initialize(SocketStreamHelper.java:59)
at com.mongodb.connection.SocketStream.open(SocketStream.java:57)
... 3 common frames omitted
- Exception in monitor thread while connecting to server localhost:27017
2020-04-10 09:47:48,396 [localhost-startStop-1] ERROR org.springframework.boot.web.embedded.tomcat.TomcatStarter - Error starting Tomcat context. Exception: org.springframework.beans.factory.BeanCreationException. Message: Error creating bean with name 'servletEndpointRegistrar' defined in class path resource [org/springframework/boot/actuate/autoconfigure/endpoint/web/ServletEndpointManagementContextConfiguration$WebMvcServletEndpointManagementContextConfiguration.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.boot.actuate.endpoint.web.ServletEndpointRegistrar]: Factory method 'servletEndpointRegistrar' threw exception; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'healthEndpoint' defined in class path resource [org/springframework/boot/actuate/autoconfigure/health/HealthEndpointConfiguration.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.boot.actuate.health.HealthEndpoint]: Factory method 'healthEndpoint' threw exception; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.boot.actuate.autoconfigure.jdbc.DataSourceHealthIndicatorAutoConfiguration': Bean instantiation via constructor failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.boot.actuate.autoconfigure.jdbc.DataSourceHealthIndicatorAutoConfiguration$$EnhancerBySpringCGLIB$$ad1b39b4]: Constructor threw exception; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dataSource' defined in class path resource [org/springframework/boot/autoconfigure/jdbc/DataSourceConfiguration$Hikari.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.zaxxer.hikari.HikariDataSource]: Factory method 'dataSource' threw exception; nested exception is org.springframework.boot.autoconfigure.jdbc.DataSourceProperties$DataSourceBeanCreationException: Failed to determine a suitable driver class
2020-04-10 09:47:48,410 [main] INFO org.apache.catalina.core.StandardService - Stopping service [Tomcat]因为清楚该项目不需要配置mongodb连接，所以我们可以屏蔽mongodb的加载，具体做法在Spring boot 启动类Application的注解@SpringBootAppliation(exclude = { MongoAutoConfiguration.class, MongoDataAutoConfiguration.class})，然后重新编译启动，发现依然失败！但是问题异常信息变了，日志如下：
2020-04-10 10:19:55,390 [localhost-startStop-1] ERROR org.springframework.boot.web.embedded.tomcat.TomcatStarter - Error starting Tomcat context. Exception: org.springframework.beans.factory.BeanCreationException. Message: Error creating bean with name 'servletEndpointRegistrar' defined in class path resource [org/springframework/boot/actuate/autoconfigure/endpoint/web/ServletEndpointManagementContextConfiguration$WebMvcServletEndpointManagementContextConfiguration.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.boot.actuate.endpoint.web.ServletEndpointRegistrar]: Factory method 'servletEndpointRegistrar' threw exception; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'healthEndpoint' defined in class path resource [org/springframework/boot/actuate/autoconfigure/health/HealthEndpointConfiguration.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.boot.actuate.health.HealthEndpoint]: Factory method 'healthEndpoint' threw exception; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.boot.actuate.autoconfigure.jdbc.DataSourceHealthIndicatorAutoConfiguration': Bean instantiation via constructor failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.boot.actuate.autoconfigure.jdbc.DataSourceHealthIndicatorAutoConfiguration$$EnhancerBySpringCGLIB$$b3ab18de]: Constructor threw exception; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dataSource' defined in class path resource [org/springframework/boot/autoconfigure/jdbc/DataSourceConfiguration$Hikari.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.zaxxer.hikari.HikariDataSource]: Factory method 'dataSource' threw exception; nested exception is org.springframework.boot.autoconfigure.jdbc.DataSourceProperties$DataSourceBeanCreationException: Failed to determine a suitable driver class
2020-04-10 10:19:55,406 [main] INFO org.apache.catalina.core.StandardService - Stopping service [Tomcat]
2020-04-10 10:19:55,415 [main] WARN o.s.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext - Exception encountered during context initialization - cancelling refresh attempt: org.springframework.context.ApplicationContextException: Unable to start web server; nested exception is org.springframework.boot.web.server.WebServerException: Unable to start embedded Tomcat
2020-04-10 10:19:55,426 [main] INFO o.s.boot.autoconfigure.logging.ConditionEvaluationReportLoggingListener -
Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2020-04-10 10:19:55,432 [main] ERROR org.springframework.boot.diagnostics.LoggingFailureAnalysisReporter -
***************************
APPLICATION FAILED TO START
***************************
Description:
Failed to configure a DataSource: 'url' attribute is not specified and no embedded datasource could be configured.
Reason: Failed to determine a suitable driver class
Action:
Consider the following:
If you want an embedded database (H2, HSQL or Derby), please put it on the classpath.
If you have database settings to be loaded from a particular profile you may need to activate it (the profiles dev are currently active).这次没有提示加载mongodb连接失败，但是仍然提示加载dataSource失败，也就是说dataSource在启动时仍然在加载，那我们继续排除，在启动类中加入DataSourceAutoConfiguration.class，然后启动，这次正常了！
总结：由于项目中 有部分依赖外部的版本是SNAPSHOT版，存在外部发不了不稳定的版本，导致项目启动失败。完整配置如下：
@SpringBootApplication(exclude = { DataSourceAutoConfiguration.class ,MongoAutoConfiguration.class, MongoDataAutoConfiguration.class})