登陆Opencms工作区：出现Communications link failure错误。
??????????SQL?????: Communications link failureThe last packet successfully received from the server was 33,537,195 milliseconds ago. The last packet sent successfully to the server was 0 milliseconds ago.??: Can not read response from server. Expected to read 4 bytes, read 0 bytes before connection was unexpectedly los
org.opencms.db.CmsDbSqlException: An SQL error occurred when executing the following query: com.mysql.jdbc.JDBC4PreparedStatement@b38908: EXCEPTION: com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: No operations allowed after statement closed..
at org.opencms.db.generic.CmsVfsDriver.readResource(CmsVfsDriver.java:2327) 
原因：
Mysql服务器默认的“wait_timeout”是8小时（也就是默认的值默认是28800秒），也就是说一个connection空闲超过8个小时，Mysql将自动断开该connection，通俗的讲就是一个连接在8小时内没有活动，就会自动断开该连接。而连接池却认为该连接还是有效的(因为并未校验连接的有效性)，当应用申请使用该连接时，就会导致上面的报错。
wait timeout的值可以设定，但最多只能是2147483，不能再大了。也就是约24.85天
解决办法：
linux系统：编辑 /etc/mysql/my.cnf文件。
wait_timeout=1814400
interactive_timeout=1814400
window系统：修改方法：找到MySQL目录下my.ini文件， 在
# The TCP/IP Port the MySQL Server will listen on
port=3306下面添加
# this is myown dinifition for mysql connection timeout
wait_timeout=181440
interactive_timeout=181440