自己的小网站在测试机器上长时间不访问后（默认8小时过期），再次访问发现有如下错误：
Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: The last packet successfully received fro
m the server was 63,020,509 milliseconds ago. The last packet sent successfully to the server was 63,020,509
milliseconds ago. is longer than the server configured value of 'wait_timeout'. You should consider either e
xpiring and/or testing connection validity before use in your application, increasing the server configured v
alues for client timeouts, or using the Connector/J connection property 'autoReconnect=true' to avoid this pr
oblem.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:4
5)
at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1116)
at com.mysql.jdbc.MysqlIO.send(MysqlIO.java:3851)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2471)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2651)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2683)
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2144)
at com.mysql.jdbc.PreparedStatement.execute(PreparedStatement.java:1379)
at org.apache.tomcat.dbcp.dbcp.DelegatingPreparedStatement.execute(DelegatingPreparedStatement.java:172)
at org.apache.tomcat.dbcp.dbcp.DelegatingPreparedStatement.execute(DelegatingPreparedStatement.java:172)
Fix: If only the connection pool could check if the the connection it is about to return is live or not, the porblem is fixed. This can be done in apache-common-dbcp (I know this one coz I used it, please look into documentation of the connection-pool you are using). Here’s how you do it: You add the following properties to dbcp configuration.
- validationQuery=”SELECT 1″
- testOnBorrow=”true”
And that does the trick.
暂时我对我的mysql连接加上： 试试效果
validationQuery="SELECT 1"
testOnBorrow
=
"true"
目前我不想添加： autoReconnect=true 因为我对此的理解不深，mysql文档这样写的：
This parameter is false by default. This forces disconnected API nodes (including MySQL Servers acting as SQL nodes) to use a new connection to the cluster rather than attempting to re-use an existing one, as re-use of connections can cause problems when using dynamically-allocated node IDs. (Bug #45921)
如果有问题再添加 autoReconnect选项
like this:
<Resource name="jdbc/saasNetTest" auth="Container" type="javax.sql.DataSource"
initialSize="10" maxActive="100" maxIdle="30" maxWait="10000"
username="***" password="***" driverClassName="com.mysql.jdbc.Driver"
url="jdbc:mysql://localhost:3306/saasNetTest"
validationQuery="SELECT 1"
testOnBorrow="true"
/>
参考文档：http://stackoverflow.com/questions/9674165/mysql-jdbc-timeout-even-with-autoreconnect-true
http://amitcodes.com/2008/07/26/16/
http://www.tomcatexpert.com/blog/2010/04/01/configuring-jdbc-pool-high-concurrency