com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure

长时间不用数据里报错

The last packet successfully received from the server was 5,281,201 milliseconds ago. The last packet sent successfully to the server was 5,281,218 milliseconds ago.

at sun.reflect.GeneratedConstructorAccessor192.newInstance(Unknown Source) ~[na:na]

at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.8.0_221]

at java.lang.reflect.Constructor.newInstance(Constructor.java:423) ~[na:1.8.0_221]

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.clearInputStream(NativeProtocol.java:837) ~[mysql-connector-java-8.0.16.jar:8.0.16]

at com.mysql.cj.protocol.a.NativeProtocol.sendCommand(NativeProtocol.java:652) ~[mysql-connector-java-8.0.16.jar:8.0.16]

at com.mysql.cj.protocol.a.NativeProtocol.sendQueryPacket(NativeProtocol.java:986) ~[mysql-connector-java-8.0.16.jar:8.0.16]

at com.mysql.cj.NativeSession.execSQL(NativeSession.java:1168) ~[mysql-connector-java-8.0.16.jar:8.0.16]

at com.mysql.cj.jdbc.ClientPreparedStatement.executeInternal(ClientPreparedStatement.java:932) ~[mysql-connector-java-8.0.16.jar:8.0.16]

... 170 common frames omitted

Caused by: java.io.IOException: Socket is closed

at com.mysql.cj.protocol.AbstractSocketConnection.getMysqlInput(AbstractSocketConnection.java:72) ~[mysql-connector-java-8.0.16.jar:8.0.16]

at com.mysql.cj.protocol.a.NativeProtocol.clearInputStream(NativeProtocol.java:833) ~[mysql-connector-java-8.0.16.jar:8.0.16]

... 174 common frames omitted

解决方案：

添加参数testOnBorrow=true 每当拿到一个连接进行使用时，测试是否可用，不可用删除。