MySQL自动关闭连接导致DBCP报错

原因是DBCP保持连接的超时时间比MySQL连接超时时间长。mysql配置中的wait_timeout值一定要大于等于连接池的idle_timeout值，否则

长时间不操作页面后，再操作时程序就会报错，异常如下：

com.mysql.jdbc.exceptions.jdbc4.CommunicationsException:Communications link failure

Thelast packet successfully received from the server was 8,064,672 millisecondsago. The last packet sent successfully to the server was 8,064,672 millisecondsago.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
atsun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
atsun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:409)
at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1122)
at com.mysql.jdbc.MysqlIO.send(MysqlIO.java:3317)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1941)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2114)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2696)
atcom.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2105)
at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:2264)
at org.apache.commons.dbcp.DelegatingPreparedStatement.executeQuery(DelegatingPreparedStatement.java:96)
atorg.apache.commons.dbcp.DelegatingPreparedStatement.executeQuery(DelegatingPreparedStatement.java:96)
atorg.apache.commons.dbcp.DelegatingPreparedStatement.executeQuery(DelegatingPreparedStatement.java:96)
...
Caused by: java.net.SocketException: Connection reset by peer: socket writeerror
at java.net.SocketOutputStream.socketWrite0(Native Method)
at java.net.SocketOutputStream.socketWrite(SocketOutputStream.java:92)
at java.net.SocketOutputStream.write(SocketOutputStream.java:136)
at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:65)
at java.io.BufferedOutputStream.flush(BufferedOutputStream.java:123)
at com.mysql.jdbc.MysqlIO.send(MysqlIO.java:3298)
... 34 common frames omitted

原因是DBCP保持连接的超时时间比MySQL连接超时时间长。mysql配置中的wait_timeout值一定要大于等于连接池的idle_timeout值，，否则mysql会在wait_timeout的时间后关闭连接，然而连接池还认为该连接可用，这样就会产生异常。

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