【现象】

com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

The last packet successfully received from the server was 1 milliseconds ago.  The last packet sent successfully to the server was 1 milliseconds ago.
        at sun.reflect.GeneratedConstructorAccessor50.newInstance(Unknown Source)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
        at com.mysql.jdbc.Util.handleNewInstance(Util.java:425)
        at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:990)
        at com.mysql.jdbc.ExportControlled.transformSocketToSSLSocket(ExportControlled.java:201)
        at com.mysql.jdbc.MysqlIO.negotiateSSLConnection(MysqlIO.java:4912)
        at com.mysql.jdbc.MysqlIO.proceedHandshakeWithPluggableAuthentication(MysqlIO.java:1663)
        at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1224)
        at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2190)
        at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2221)
        at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2016)
        at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:776)
        at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
        at sun.reflect.GeneratedConstructorAccessor34.newInstance(Unknown Source)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
        at com.mysql.jdbc.Util.handleNewInstance(Util.java:425)
        at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:386)
        at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:330)
        at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1644)
        at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1710)
        at com.alibaba.druid.pool.DruidDataSource$CreateConnectionThread.run(DruidDataSource.java:2774)
Caused by: javax.net.ssl.SSLHandshakeException: No appropriate protocol (protocol is disabled or cipher suites are inappropriate)
        at sun.security.ssl.HandshakeContext.<init>(HandshakeContext.java:171)
        at sun.security.ssl.ClientHandshakeContext.<init>(ClientHandshakeContext.java:106)
        at sun.security.ssl.TransportContext.kickstart(TransportContext.java:238)
        at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:410)
        at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:389)
        at com.mysql.jdbc.ExportControlled.transformSocketToSSLSocket(ExportControlled.java:186)
        ... 17 common frames omitted

【解决方法】

去掉SSLv3, TLSv1, TLSv1.1后，再启动项目，具体操作如下：

cd /usr/java/jdk1.8.0_341-amd64/jre/lib/security
vi java.security 
jdk.tls.disabledAlgorithms=SSLv3, TLSv1, TLSv1.1,RC4, DES, MD5withRSA,
    DH keySize < 1024, EC keySize < 224, 3DES_EDE_CBC, anon, NULL,
    include jdk.disabled.namedCurves
修改为：
jdk.tls.disabledAlgorithms=RC4, DES, MD5withRSA,
    DH keySize < 1024, EC keySize < 224, 3DES_EDE_CBC, anon, NULL,
    include jdk.disabled.namedCurves