Error message:

com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
	at com.mysql.cj.jdbc.exceptions.SQLError.createCommunicationsException(SQLError.java:174) ~[mysql-connector-java-8.0.18.jar:8.0.18]
	at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:64) ~[mysql-connector-java-8.0.18.jar:8.0.18]
	at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:836) ~[mysql-connector-java-8.0.18.jar:8.0.18]
	at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:456) ~[mysql-connector-java-8.0.18.jar:8.0.18]
	at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:246) ~[mysql-connector-java-8.0.18.jar:8.0.18]
	at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:199) ~[mysql-connector-java-8.0.18.jar:8.0.18]
	at com.alibaba.druid.filter.FilterChainImpl.connection_connect(FilterChainImpl.java:156) ~[druid-1.1.10.jar:1.1.10]
	at com.alibaba.druid.filter.stat.StatFilter.connection_connect(StatFilter.java:218) ~[druid-1.1.10.jar:1.1.10]
	at com.alibaba.druid.filter.FilterChainImpl.connection_connect(FilterChainImpl.java:150) ~[druid-1.1.10.jar:1.1.10]
	at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1560) ~[druid-1.1.10.jar:1.1.10]
	at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1623) ~[druid-1.1.10.jar:1.1.10]
	at com.alibaba.druid.pool.DruidDataSource.init(DruidDataSource.java:861) ~[druid-1.1.10.jar:1.1.10]
	at com.alibaba.druid.pool.DruidDataSource.getConnection(DruidDataSource.java:1229) ~[druid-1.1.10.jar:1.1.10]
	at com.alibaba.druid.pool.DruidDataSource.getConnection(DruidDataSource.java:1225) ~[druid-1.1.10.jar:1.1.10]
	at com.alibaba.druid.pool.DruidDataSource.getConnection(DruidDataSource.java:90) ~[druid-1.1.10.jar:1.1.10]
	at org.springframework.jdbc.datasource.DataSourceTransactionManager.doBegin(DataSourceTransactionManager.java:263) ~[spring-jdbc-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at org.springframework.transaction.support.AbstractPlatformTransactionManager.getTransaction(AbstractPlatformTransactionManager.java:376) ~[spring-tx-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at org.springframework.transaction.interceptor.TransactionAspectSupport.createTransactionIfNecessary(TransactionAspectSupport.java:560) ~[spring-tx-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:347) ~[spring-tx-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:99) ~[spring-tx-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:747) ~[spring-aop-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:689) ~[spring-aop-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at com.baidu.fsg.uid.worker.DisposableWorkerIdAssigner$$EnhancerBySpringCGLIB$$17ab474d.assignWorkerId(<generated>) ~[classes/:?]
	at com.baidu.fsg.uid.impl.DefaultUidGenerator.afterPropertiesSet(DefaultUidGenerator.java:89) ~[classes/:?]
	at com.baidu.fsg.uid.impl.CachedUidGenerator.afterPropertiesSet(CachedUidGenerator.java:69) ~[classes/:?]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1862) ~[spring-beans-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1799) ~[spring-beans-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:595) ~[spring-beans-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:517) ~[spring-beans-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:323) ~[spring-beans-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:321) ~[spring-beans-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) ~[spring-beans-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:276) ~[spring-beans-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1287) ~[spring-beans-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1207) ~[spring-beans-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.autowireResource(CommonAnnotationBeanPostProcessor.java:537) ~[spring-context-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.getResource(CommonAnnotationBeanPostProcessor.java:513) ~[spring-context-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor$ResourceElement.getResourceToInject(CommonAnnotationBeanPostProcessor.java:653) ~[spring-context-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at org.springframework.beans.factory.annotation.InjectionMetadata$InjectedElement.inject(InjectionMetadata.java:224) ~[spring-beans-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:116) ~[spring-beans-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.postProcessProperties(CommonAnnotationBeanPostProcessor.java:334) ~[spring-context-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1429) ~[spring-beans-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:594) ~[spring-beans-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:517) ~[spring-beans-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:323) ~[spring-beans-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) [spring-beans-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:321) [spring-beans-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) [spring-beans-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:879) [spring-beans-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:878) [spring-context-5.2.0.RELEASE.jar:5.2.0.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:550) [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 cn.com.icbf.framework.uid.UidStartApplication.main(UidStartApplication.java:20) [classes/:?]
Caused by: com.mysql.cj.exceptions.CJCommunicationsException: Communications link failure

Solution:

This is because MySQL needs to specify whether to connect with SSL in the higher version: ?useSSL=false