尝试创建数据库连接时出现异常

Question

我正在使用 MySQL 工作台和基于 maven 的 java 应用程序，我正在尝试将本地数据库连接到我的代码。当我这样做时，我收到以下错误。 请指导可能的错误。

Cannot create database connection
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 java.sql.DriverManager.getConnection(DriverManager.java:664)
    at java.sql.DriverManager.getConnection(DriverManager.java:247)
    at DBconnection.createNewDBconnection(DBconnection.java:14)
    at ReadExcelFileDemo.main(ReadExcelFileDemo.java:102)
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(NativeConstructorAccessorImpl.java:62)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
    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)
    ... 7 more
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:98)
    at sun.security.ssl.TransportContext.kickstart(TransportContext.java:220)
    at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:428)
    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)
    ... 14 more
Exception in thread "main" java.lang.NullPointerException
    at ReadExcelFileDemo.main(ReadExcelFileDemo.java:104)

Process finished with exit code 1

Answer 1

由于服务器问题或连接设置错误，您的数据库无法访问。 请参考这个答案