The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.) ### The error may exist in file [D:\java\tomcat\apache-tomcat-9.0.62\webapps\ROOT\WEB-INF\classes\mapper\BookMapper.xml] ### The error may involve com.laver.bookstore.mapper.BookMapper.selectByExample ### The error occurred while executing a query ### Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is org.apache.commons.dbcp.SQLNestedException: Cannot create PoolableConnectionFactory (Communications link failure什么意思

这个错误提示表明应用程序无法获取数据库连接。"Communications link failure" 意味着数据库连接已经中断或无法建立连接，通常是由于以下原因之一导致的：

1. 数据库服务器宕机或未启动。
2. 数据库服务器上的网络连接中断。
3. 应用程序无法使用正确的用户名和密码进行身份验证。
4. 应用程序无法访问正确的数据库或数据源。

为了解决这个问题，你可以尝试以下步骤：

1. 确认数据库服务器已启动并可以正常运行。
2. 检查网络连接，确保应用程序可以连接到数据库服务器。
3. 确认应用程序使用了正确的用户名和密码进行身份验证。
4. 确认应用程序正在连接到正确的数据库或数据源。

相关问题

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets

"The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server." 这个错误信息通常是由于数据库连接问题引起的。它指示着在与服务器通信时出现了一些错误，导致没有数据包传输成功。这可能是由于网络连接中断、服务器故障或配置错误等原因引起的。

要解决这个问题，您可以尝试以下几个步骤：
1. 检查网络连接：确保您的网络连接正常并且没有中断。尝试重新连接网络或检查网络配置。
2. 检查服务器状态：确认服务器是否正常运行并且没有故障。您可以尝试重启服务器并检查服务器日志以查找可能的错误信息。
3. 检查数据库配置：确保您的数据库连接配置正确。检查数据库地址、端口号、用户名和密码等信息是否正确。
4. 检查防火墙设置：如果您的服务器在防火墙后面，请确保防火墙允许数据库连接的流量通过。

如果您尝试了以上步骤但问题仍然存在，您可能需要进一步检查数据库和应用程序的配置和日志以查找更详细的错误信息。

he last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server

这个错误" The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server."通常是由于数据库连接问题引起的。其中可能的原因有以下几种:

1. 数据库连接被回收: 这种情况下，系统的缓冲池不知道连接已经被回收，继续使用已经被回收的连接导致错误。<span class="em">1</span><span class="em">2</span><span class="em">3</span>
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