报错如下：
org.springframework.boot.web.server.WebServerException: Unable to start embedded Tomcat server
at org.springframework.boot.web.embedded.tomcat.TomcatWebServer.start(TomcatWebServer.java:215) ~[spring-boot-2.2.0.RELEASE.jar:2.2.0.RELEASE]
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.startWebServer(ServletWebServerApplicationContext.java:297) ~[spring-boot-2.2.0.RELEASE.jar:2.2.0.RELEASE]
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.finishRefresh(ServletWebServerApplicationContext.java:163) ~[spring-boot-2.2.0.RELEASE.jar:2.2.0.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:553) ~[spring-context-5.2.0.RELEASE.jar:5.2.0.RELEASE]
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:141) ~[spring-boot-2.2.0.RELEASE.jar:2.2.0.RELEASE]
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:747) [spring-boot-2.2.0.RELEASE.jar:2.2.0.RELEASE]
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397) [spring-boot-2.2.0.RELEASE.jar:2.2.0.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:315) [spring-boot-2.2.0.RELEASE.jar:2.2.0.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226) [spring-boot-2.2.0.RELEASE.jar:2.2.0.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1215) [spring-boot-2.2.0.RELEASE.jar:2.2.0.RELEASE]
at com.example.demo.DemoApplication.main(DemoApplication.java:10) [classes/:na]
Caused by: java.lang.IllegalArgumentException: standardService.connector.startFailed
at org.apache.catalina.core.StandardService.addConnector(StandardService.java:231) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
at org.springframework.boot.web.embedded.tomcat.TomcatWebServer.addPreviouslyRemovedConnectors(TomcatWebServer.java:278) ~[spring-boot-2.2.0.RELEASE.jar:2.2.0.RELEASE]
at org.springframework.boot.web.embedded.tomcat.TomcatWebServer.start(TomcatWebServer.java:197) ~[spring-boot-2.2.0.RELEASE.jar:2.2.0.RELEASE]
... 10 common frames omitted
Caused by: org.apache.catalina.LifecycleException: Protocol handler start failed
at org.apache.catalina.connector.Connector.startInternal(Connector.java:1008) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
at org.apache.catalina.core.StandardService.addConnector(StandardService.java:227) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
... 12 common frames omitted
Caused by: java.net.SocketException: Permission denied
at sun.nio.ch.Net.bind0(Native Method) ~[na:1.8.0_144]
at sun.nio.ch.Net.bind(Net.java:433) ~[na:1.8.0_144]
at sun.nio.ch.Net.bind(Net.java:425) ~[na:1.8.0_144]
at sun.nio.ch.ServerSocketChannelImpl.bind(ServerSocketChannelImpl.java:223) ~[na:1.8.0_144]
at sun.nio.ch.ServerSocketAdaptor.bind(ServerSocketAdaptor.java:74) ~[na:1.8.0_144]
at org.apache.tomcat.util.net.NioEndpoint.initServerSocket(NioEndpoint.java:230) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
at org.apache.tomcat.util.net.NioEndpoint.bind(NioEndpoint.java:213) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
at org.apache.tomcat.util.net.AbstractEndpoint.bindWithCleanup(AbstractEndpoint.java:1124) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
at org.apache.tomcat.util.net.AbstractEndpoint.start(AbstractEndpoint.java:1210) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
at org.apache.coyote.AbstractProtocol.start(AbstractProtocol.java:586) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
at org.apache.catalina.connector.Connector.startInternal(Connector.java:1005) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
... 14 common frames omitted
Caused by: java.net.SocketException: Permission denied
原因是tomcat的端口号被其他应用占用，更改tomcat的端口号，server.prot=XXXX