载自：https://blog.csdn.net/ponxbin/article/details/80608040
关于版本比较新的数据库（Mysql8.0）连接的问题：
he 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:172)
at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:64)
at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:862)
at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:444)
at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:230)
at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:226)
at java.sql.DriverManager.getConnection(Unknown Source)
at java.sql.DriverManager.getConnection(Unknown Source)
at mysqlconnect.connect.main(connect.java:24)
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)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:59)
at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:103)
at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:149)
at com.mysql.cj.exceptions.ExceptionFactory.createCommunicationsException(ExceptionFactory.java:165)
at com.mysql.cj.protocol.a.NativeProtocol.negotiateSSLConnection(NativeProtocol.java:355)
at com.mysql.cj.protocol.a.NativeAuthenticationProvider.negotiateSSLConnection(NativeAuthenticationProvider.java:789)
at com.mysql.cj.protocol.a.NativeAuthenticationProvider.proceedHandshakeWithPluggableAuthentication(NativeAuthenticationProvider.java:499)
at com.mysql.cj.protocol.a.NativeAuthenticationProvider.connect(NativeAuthenticationProvider.java:217)
at com.mysql.cj.protocol.a.NativeProtocol.connect(NativeProtocol.java:1411)
at com.mysql.cj.NativeSession.connect(NativeSession.java:165)
at com.mysql.cj.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:982)
at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:852)
... 6 more
Caused by: javax.net.ssl.SSLHandshakeException: java.security.cert.CertificateException: java.security.cert.CertPathValidatorException: Path does not chain with any of the trust anchors
at sun.security.ssl.Alerts.getSSLException(Unknown Source)
at sun.security.ssl.SSLSocketImpl.fatal(Unknown Source)
at sun.security.ssl.Handshaker.fatalSE(Unknown Source)
at sun.security.ssl.Handshaker.fatalSE(Unknown Source)
at sun.security.ssl.ClientHandshaker.serverCertificate(Unknown Source)
at sun.security.ssl.ClientHandshaker.processMessage(Unknown Source)
at sun.security.ssl.Handshaker.processLoop(Unknown Source)
at sun.security.ssl.Handshaker.process_record(Unknown Source)
at sun.security.ssl.SSLSocketImpl.readRecord(Unknown Source)
at sun.security.ssl.SSLSocketImpl.performInitialHandshake(Unknown Source)
at sun.security.ssl.SSLSocketImpl.startHandshake(Unknown Source)
at sun.security.ssl.SSLSocketImpl.startHandshake(Unknown Source)
at com.mysql.cj.protocol.ExportControlled.performTlsHandshake(ExportControlled.java:213)
at com.mysql.cj.protocol.StandardSocketFactory.performTlsHandshake(StandardSocketFactory.java:206)
at com.mysql.cj.protocol.a.NativeSocketConnection.performTlsHandshake(NativeSocketConnection.java:99)
at com.mysql.cj.protocol.a.NativeProtocol.negotiateSSLConnection(NativeProtocol.java:350)
... 13 more
Caused by: java.security.cert.CertificateException: java.security.cert.CertPathValidatorException: Path does not chain with any of the trust anchors
at com.mysql.cj.protocol.ExportControlled$X509TrustManagerWrapper.checkServerTrusted(ExportControlled.java:280)
at sun.security.ssl.AbstractTrustManagerWrapper.checkServerTrusted(Unknown Source)
... 25 more
Caused by: java.security.cert.CertPathValidatorException: Path does not chain with any of the trust anchors
at sun.security.provider.certpath.PKIXCertPathValidator.validate(Unknown Source)
at sun.security.provider.certpath.PKIXCertPathValidator.engineValidate(Unknown Source)
at java.security.cert.CertPathValidator.validate(Unknown Source)
at com.mysql.cj.protocol.ExportControlled$X509TrustManagerWrapper.checkServerTrusted(ExportControlled.java:273)
... 26 more
Exception in thread "main" java.lang.NullPointerException
at mysqlconnect.connect.main(connect.java:34)
网上说的什么修改的方法对我没有用
诸如此类：
1·修改my.ini bind-address = 127.0.0.1 为 bind-address = 0.0.0.0 使非本地网络可以访问数据库
2·检查防火墙是否有开放3306端口
3·网上广为流传的86400秒超时 回收机制 并不和我遇到的问题一致，这种问题是在程序运行过程中因为我们使用的连接池不知道连接被回收了所以报出的异常，解决方案可以是修改连接池配置或修改mysql空闲超时时间配置。
以上方法均没用，主要是mysql和驱动版本的问题
我的mysql是8.0,驱动也是8.x最新的；
Class.forName("com.mysql.cj.jdbc.Driver");
url = "jdbc:mysql://localhost:3306/jnditest?serverTimezone=GMT&useSSL=false";//数据库的路径
主要是红色字体方面，serverTimezone缺失是很容易从错误找出来的，但是重点是useSSL=false，这个从错误提示是看不出来的，它有个很重要的作用是使用JDBC跟你的数据库连接的时候，你的JDBC版本与MySQL版本不兼容，MySQL的版本更高一些，在连接语句后加上“useSSL=‘true’” ，就可以连接到数据库了。更高版本。但如果是兼容版本的话就会出错。
我试了改成true的确又出现了这个问题。
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原文链接：https://blog.csdn.net/ponxbin/article/details/80608040