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一个用java swing开发的销售点系统不时地抛出以下异常，并不是每次都发生。 我们在这里发现了一个类似的问题。Mysql数据库记录缺失，但肯定是在本地插入并记录下来的
com.mysql.cj.jdbc.exception.CommunicationsException。通信链接失败
读取超时造成的
我翻阅了其他问题和答案，但我找不到合适的答案来解决我所遇到的具体问题。尤其是 "com.mysql.cj.jdbc.exception.CommunicationsException.Communications link failure caused by Read time out"。Communications link failure caused by Read time out"
为什么会出现这种异常？
以下是POS系统在控制台中抛出的具体异常。
Sep 07, 2018 7:15:05 AM persistanceOperations.TransactionOperations view
SEVERE: null
com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure
The last packet successfully received from the server was 5,402,907 milliseconds ago. The last packet sent successfully to the server was 5,402,909 milliseconds ago.
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.ClientPreparedStatement.executeInternal(ClientPreparedStatement.java:975)
at com.mysql.cj.jdbc.ClientPreparedStatement.executeQuery(ClientPreparedStatement.java:1025)
at persistanceOperations.TransactionOperations.view(TransactionOperations.java:146)
at ui.Selling.loadLastestSales(Selling.java:4647)
at ui.Selling.<init>(Selling.java:239)
at ui.Operation.sellingActionPerformed(Operation.java:355)
at ui.Operation.access$800(Operation.java:36)
at ui.Operation$9.actionPerformed(Operation.java:245)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$500(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
Caused by: com.mysql.cj.exceptions.CJCommunicationsException: Communications link failure
The last packet successfully received from the server was 5,402,907 milliseconds ago. The last packet sent successfully to the server was 5,402,909 milliseconds ago.
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: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.readMessage(NativeProtocol.java:556)
at com.mysql.cj.protocol.a.NativeProtocol.checkErrorMessage(NativeProtocol.java:726)
at com.mysql.cj.protocol.a.NativeProtocol.sendCommand(NativeProtocol.java:665)
at com.mysql.cj.protocol.a.NativeProtocol.sendQueryPacket(NativeProtocol.java:980)
at com.mysql.cj.NativeSession.execSQL(NativeSession.java:1185)
at com.mysql.cj.jdbc.ClientPreparedStatement.executeInternal(ClientPreparedStatement.java:952)
... 43 more
Caused by: java.net.SocketTimeoutException: Read timed out
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.socketRead(Unknown Source)
at java.net.SocketInputStream.read(Unknown Source)
at java.net.SocketInputStream.read(Unknown Source)
at com.mysql.cj.protocol.ReadAheadInputStream.fill(ReadAheadInputStream.java:107)
at com.mysql.cj.protocol.ReadAheadInputStream.readFromUnderlyingStreamIfNecessary(ReadAheadInputStream.java:150)
at com.mysql.cj.protocol.ReadAheadInputStream.read(ReadAheadInputStream.java:180)
at java.io.FilterInputStream.read(Unknown Source)
at com.mysql.cj.protocol.FullReadInputStream.readFully(FullReadInputStream.java:64)
at com.mysql.cj.protocol.a.SimplePacketReader.readHeader(SimplePacketReader.java:63)
at com.mysql.cj.protocol.a.SimplePacketReader.readHeader(SimplePacketReader.java:45)
at com.mysql.cj.protocol.a.TimeTrackingPacketReader.readHeader(TimeTrackingPacketReader.java:52)
at com.mysql.cj.protocol.a.TimeTrackingPacketReader.readHeader(TimeTrackingPacketReader.java:41)
at com.mysql.cj.protocol.a.MultiPacketReader.readHeader(MultiPacketReader.java:54)
at com.mysql.cj.protocol.a.MultiPacketReader.readHeader(MultiPacketReader.java:44)
at com.mysql.cj.protocol.a.NativeProtocol.readMessage(NativeProtocol.java:550)
... 48 more
