Caused by: org.yaml.snakeyaml.parser.ParserException: while parsing a block mapping

 [main] ERROR org.springframework.boot.SpringApplication - Application run failed
java.lang.IllegalStateException: Failed to load property source from location 'classpath:/application.yml'
	at org.springframework.boot.context.config.ConfigFileApplicationListener$Loader.load(ConfigFileApplicationListener.java:535)
	at org.springframework.boot.context.config.ConfigFileApplicationListener$Loader.loadForFileExtension(ConfigFileApplicationListener.java:494)
	at org.springframework.boot.context.config.ConfigFileApplicationListener$Loader.load(ConfigFileApplicationListener.java:462)
	at org.springframework.boot.context.config.ConfigFileApplicationListener$Loader.lambda$null$4(ConfigFileApplicationListener.java:444)
	at java.lang.Iterable.forEach(Iterable.java:75)
	at org.springframework.boot.context.config.ConfigFileApplicationListener$Loader.lambda$load$5(ConfigFileApplicationListener.java:443)
	at java.lang.Iterable.forEach(Iterable.java:75)
	at org.springframework.boot.context.config.ConfigFileApplicationListener$Loader.load(ConfigFileApplicationListener.java:440)
	at org.springframework.boot.context.config.ConfigFileApplicationListener$Loader.load(ConfigFileApplicationListener.java:331)
	at org.springframework.boot.context.config.ConfigFileApplicationListener.addPropertySources(ConfigFileApplicationListener.java:213)
	at org.springframework.boot.context.config.ConfigFileApplicationListener.postProcessEnvironment(ConfigFileApplicationListener.java:196)
	at org.springframework.boot.context.config.ConfigFileApplicationListener.onApplicationEnvironmentPreparedEvent(ConfigFileApplicationListener.java:183)
	at org.springframework.boot.context.config.ConfigFileApplicationListener.onApplicationEvent(ConfigFileApplicationListener.java:169)
	at org.springframework.context.event.SimpleApplicationEventMulticaster.doInvokeListener(SimpleApplicationEventMulticaster.java:172)
	at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:165)
	at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:139)
	at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:127)
	at org.springframework.boot.context.event.EventPublishingRunListener.environmentPrepared(EventPublishingRunListener.java:74)
	at org.springframework.boot.SpringApplicationRunListeners.environmentPrepared(SpringApplicationRunListeners.java:54)
	at org.springframework.boot.SpringApplication.prepareEnvironment(SpringApplication.java:351)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:317)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1246)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1234)
	at cn.first.Application.main(Application.java:13)
Caused by: org.yaml.snakeyaml.parser.ParserException: while parsing a block mapping
 in 'reader', line 1, column 1:
    server:
    ^
expected , but found BlockMappingStart
 in 'reader', line 22, column 3:
      type: com.alibaba.druid.pool.Dru ... 
      ^

	at org.yaml.snakeyaml.parser.ParserImpl$ParseBlockMappingKey.produce(ParserImpl.java:571)
	at org.yaml.snakeyaml.parser.ParserImpl.peekEvent(ParserImpl.java:157)
	at org.yaml.snakeyaml.parser.ParserImpl.checkEvent(ParserImpl.java:147)
	at org.yaml.snakeyaml.composer.Composer.composeMappingNode(Composer.java:227)
	at org.yaml.snakeyaml.composer.Composer.composeNode(Composer.java:154)
	at org.yaml.snakeyaml.composer.Composer.composeDocument(Composer.java:122)
	at org.yaml.snakeyaml.composer.Composer.getNode(Composer.java:84)
	at org.yaml.snakeyaml.constructor.BaseConstructor.getData(BaseConstructor.java:123)
	at org.yaml.snakeyaml.Yaml$1.next(Yaml.java:547)
	at org.springframework.beans.factory.config.YamlProcessor.process(YamlProcessor.java:161)
	at org.springframework.beans.factory.config.YamlProcessor.process(YamlProcessor.java:139)
	at org.springframework.boot.env.OriginTrackedYamlLoader.load(OriginTrackedYamlLoader.java:72)
	at org.springframework.boot.env.YamlPropertySourceLoader.load(YamlPropertySourceLoader.java:50)
	at org.springframework.boot.context.config.ConfigFileApplicationListener$Loader.loadDocuments(ConfigFileApplicationListener.java:542)
	at org.springframework.boot.context.config.ConfigFileApplicationListener$Loader.load(ConfigFileApplicationListener.java:515)
	... 23 common frames omitted

Process finished with exit code 1

一般遇到这种情况，首先看下yml格式是否有误。
百度“yml格式化校验” 或者点这里
如果格式没有检测出问题，具体原因请自行查明