报错描述
2021-12-18 22:47:14.834 ERROR 20196 --- [reate-940563698] com.alibaba.druid.pool.DruidDataSource   : create connection SQLException, url: jdbc:mysql://localhost:3306/renrenfast?useUnicode=true&characterEncoding=UTF-8&serverTimezone=Asia/Shanghai, errorCode 0, state 08S01
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)
        at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:64)
        at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:827)
        at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:447)
        at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:237)
        at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:199)
        at com.alibaba.druid.filter.FilterChainImpl.connection_connect(FilterChainImpl.java:156)
        at com.alibaba.druid.filter.FilterAdapter.connection_connect(FilterAdapter.java:786)
        at com.alibaba.druid.filter.FilterChainImpl.connection_connect(FilterChainImpl.java:150)
        at com.alibaba.druid.filter.stat.StatFilter.connection_connect(StatFilter.java:218)
        at com.alibaba.druid.filter.FilterChainImpl.connection_connect(FilterChainImpl.java:150)
        at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1572)
        at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1636)
        at com.alibaba.druid.pool.DruidDataSource$CreateConnectionThread.run(DruidDataSource.java:2550)
Caused by: com.mysql.cj.exceptions.CJCommunicationsException: 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 java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
        at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
        at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
        at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:490)
        at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:61)
        at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:105)
        at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:151)
        at com.mysql.cj.exceptions.ExceptionFactory.createCommunicationsException(ExceptionFactory.java:167)
        at com.mysql.cj.protocol.a.NativeProtocol.negotiateSSLConnection(NativeProtocol.java:340)
        at com.mysql.cj.protocol.a.NativeAuthenticationProvider.negotiateSSLConnection(NativeAuthenticationProvider.java:777)
        at com.mysql.cj.protocol.a.NativeAuthenticationProvider.proceedHandshakeWithPluggableAuthentication(NativeAuthenticationProvider.java:486)
        at com.mysql.cj.protocol.a.NativeAuthenticationProvider.connect(NativeAuthenticationProvider.java:202)
        at com.mysql.cj.protocol.a.NativeProtocol.connect(NativeProtocol.java:1348)
        at com.mysql.cj.NativeSession.connect(NativeSession.java:163)
        at com.mysql.cj.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:947)
        at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:817)
        ... 11 common frames omitted
Caused by: javax.net.ssl.SSLHandshakeException: Invalid Alert message: no sufficient data
        at java.base/sun.security.ssl.Alert.createSSLException(Alert.java:131)
        at java.base/sun.security.ssl.Alert.createSSLException(Alert.java:117)
        at java.base/sun.security.ssl.TransportContext.fatal(TransportContext.java:336)
        at java.base/sun.security.ssl.TransportContext.fatal(TransportContext.java:292)
        at java.base/sun.security.ssl.TransportContext.fatal(TransportContext.java:283)
        at java.base/sun.security.ssl.Alert$AlertMessage.<init>(Alert.java:196)
        at java.base/sun.security.ssl.Alert$AlertConsumer.consume(Alert.java:236)
        at java.base/sun.security.ssl.TransportContext.dispatch(TransportContext.java:185)
        at java.base/sun.security.ssl.SSLTransport.decode(SSLTransport.java:171)
        at java.base/sun.security.ssl.SSLSocketImpl.decode(SSLSocketImpl.java:1408)
        at java.base/sun.security.ssl.SSLSocketImpl.readHandshakeRecord(SSLSocketImpl.java:1314)
        at java.base/sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:440)
        at java.base/sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:411)
        at com.mysql.cj.protocol.ExportControlled.performTlsHandshake(ExportControlled.java:316)
        at com.mysql.cj.protocol.StandardSocketFactory.performTlsHandshake(StandardSocketFactory.java:188)
        at com.mysql.cj.protocol.a.NativeSocketConnection.performTlsHandshake(NativeSocketConnection.java:99)
        at com.mysql.cj.protocol.a.NativeProtocol.negotiateSSLConnection(NativeProtocol.java:331)
        ... 18 common frames omitted

配置详情
spring:
    datasource:
        type: com.alibaba.druid.pool.DruidDataSource
        druid:
            driver-class-name: com.mysql.cj.jdbc.Driver
            url: jdbc:mysql://localhost:3306/xxx?useUnicode=true&characterEncoding=UTF-8&serverTimezone=Asia/Shanghai

解决方案
只需要加上&useSSL=false
spring:
    datasource:
        type: com.alibaba.druid.pool.DruidDataSource
        druid:
            driver-class-name: com.mysql.cj.jdbc.Driver
            url: jdbc:mysql://localhost:3306/xxx?useUnicode=true&characterEncoding=UTF-8&serverTimezone=Asia/Shanghai&useSSL=false
测试效果