Java启动异常：The driver has not received any packets from the server

第一种问题

原因：驱动程序没有收到来自服务器的任何数据包，说人话就是数据库服务停止了。
这个是在linux，经过查看确实是mysql崩了，重启mysql就可以了
解决： 重启mysql：service mysqld start 或者 service mysqld restart

第二种问题

这个是在自己本地跑的，先看报错

2021-12-01 20:29:38.113 ERROR 10468 --- [Create-51362851] com.alibaba.druid.pool.DruidDataSource   : create connection SQLException, url: jdbc:mysql://localhost:3306/mall-tiny?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) ~[mysql-connector-java-8.0.16.jar:8.0.16]
	at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:64) ~[mysql-connector-java-8.0.16.jar:8.0.16]
	at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:835) ~[mysql-connector-java-8.0.16.jar:8.0.16]
	at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:455) ~[mysql-connector-java-8.0.16.jar:8.0.16]
	at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:240) ~[mysql-connector-java-8.0.16.jar:8.0.16]
	at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:199) ~[mysql-connector-java-8.0.16.jar:8.0.16]
	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$CreateConnectionThread.run(DruidDataSource.java:2468) ~[druid-1.1.10.jar:1.1.10]
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 sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.8.0_301]
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) ~[na:1.8.0_301]
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.8.0_301]
	at java.lang.reflect.Constructor.newInstance(Constructor.java:423) ~[na:1.8.0_301]
	at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:61) ~[mysql-connector-java-8.0.16.jar:8.0.16]
	at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:105) ~[mysql-connector-java-8.0.16.jar:8.0.16]
	at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:151) ~[mysql-connector-java-8.0.16.jar:8.0.16]
	at com.mysql.cj.exceptions.ExceptionFactory.createCommunicationsException(ExceptionFactory.java:167) ~[mysql-connector-java-8.0.16.jar:8.0.16]
	at com.mysql.cj.protocol.a.NativeProtocol.negotiateSSLConnection(NativeProtocol.java:361) ~[mysql-connector-java-8.0.16.jar:8.0.16]
	at com.mysql.cj.protocol.a.NativeAuthenticationProvider.negotiateSSLConnection(NativeAuthenticationProvider.java:777) ~[mysql-connector-java-8.0.16.jar:8.0.16]
	at com.mysql.cj.protocol.a.NativeAuthenticationProvider.proceedHandshakeWithPluggableAuthentication(NativeAuthenticationProvider.java:486) ~[mysql-connector-java-8.0.16.jar:8.0.16]
	at com.mysql.cj.protocol.a.NativeAuthenticationProvider.connect(NativeAuthenticationProvider.java:202) ~[mysql-connector-java-8.0.16.jar:8.0.16]
	at com.mysql.cj.protocol.a.NativeProtocol.connect(NativeProtocol.java:1452) ~[mysql-connector-java-8.0.16.jar:8.0.16]
	at com.mysql.cj.NativeSession.connect(NativeSession.java:165) ~[mysql-connector-java-8.0.16.jar:8.0.16]
	at com.mysql.cj.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:955) ~[mysql-connector-java-8.0.16.jar:8.0.16]
	at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:825) ~[mysql-connector-java-8.0.16.jar:8.0.16]
	... 9 common frames omitted
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) ~[na:1.8.0_301]
	at sun.security.ssl.ClientHandshakeContext.<init>(ClientHandshakeContext.java:101) ~[na:1.8.0_301]
	at sun.security.ssl.TransportContext.kickstart(TransportContext.java:238) ~[na:1.8.0_301]
	at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:394) ~[na:1.8.0_301]
	at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:373) ~[na:1.8.0_301]
	at com.mysql.cj.protocol.ExportControlled.performTlsHandshake(ExportControlled.java:316) ~[mysql-connector-java-8.0.16.jar:8.0.16]
	at com.mysql.cj.protocol.StandardSocketFactory.performTlsHandshake(StandardSocketFactory.java:188) ~[mysql-connector-java-8.0.16.jar:8.0.16]
	at com.mysql.cj.protocol.a.NativeSocketConnection.performTlsHandshake(NativeSocketConnection.java:99) ~[mysql-connector-java-8.0.16.jar:8.0.16]
	at com.mysql.cj.protocol.a.NativeProtocol.negotiateSSLConnection(NativeProtocol.java:352) ~[mysql-connector-java-8.0.16.jar:8.0.16]
	... 16 common frames omitted

首先第一眼，我真以为是mysql没启动起来，但是我本地另外一个项目已经连着mysql的，我刚刚关掉，不可能是mysql没启动起来或者崩掉了，接着往后面看，
直到我看到这里(也就是上面报错第38行的时候)，javax.net.ssl.SSLHandshakeException，啊 这？

网上找了一下这个报错，
说法一：找到C:\Program Files\Java\jre里面的lib\security 下面有个java.security。找到对应的SSLv3，删除掉，重启项目就好
说法二：重新安装jdk，找到项目配置jdk位置，修改为新安装的jdk
emm 都不行，说法一说的哪个文件并不能修改的
然后我去查看了另一个可以连上的url，跟这个做了一个对比
得出结论： url 后面加上 &useSSL=false,不使用SSL链接

&useSSL=false

但是为什么从前的也是同样的配置并没有报错呢，我想到了jdk版本，于是我我换了jdk试，果然的不出我所料，换了jdk版本就不需要加 &useSSL=false

最后得出结论，之前的jdk版本默认不使用SSL连接mysql，而我现在电脑上的版本默认使用SSL链接mysql，所以需要指定不使用SSL

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