com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure 解決辦法

09:00:30.307 [http-8080-6] ERROR org.hibernate.transaction.JDBCTransaction -JDBC begin failed
com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

The last packet successfully received from the server was 56,237,340 milliseconds ago.  The last packet sent successfully to the server was 1 milliseconds ago.
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.6.0_13]
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39) ~[na:1.6.0_13]
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27) ~[na:1.6.0_13]
	at java.lang.reflect.Constructor.newInstance(Constructor.java:513) ~[na:1.6.0_13]
	at com.mysql.jdbc.Util.handleNewInstance(Util.java:411) ~[mysql-connector-java-5.1.21.jar:na]
	at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1117) ~[mysql-connector-java-5.1.21.jar:na]
	at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3567) ~[mysql-connector-java-5.1.21.jar:na]
	at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3456) ~[mysql-connector-java-5.1.21.jar:na]
	at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3997) ~[mysql-connector-java-5.1.21.jar:na]
	at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2468) ~[mysql-connector-java-5.1.21.jar:na]
	at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2629) ~[mysql-connector-java-5.1.21.jar:na]
	at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2713) ~[mysql-connector-java-5.1.21.jar:na]
	at com.mysql.jdbc.ConnectionImpl.setAutoCommit(ConnectionImpl.java:5060) ~[mysql-connector-java-5.1.21.jar:na]
	at org.apache.commons.dbcp.DelegatingConnection.setAutoCommit(DelegatingConnection.java:371) ~[commons-dbcp-1.4.jar:1.4]
	at org.apache.commons.dbcp.PoolingDataSource$PoolGuardConnectionWrapper.setAutoCommit(PoolingDataSource.java:328) ~[commons-dbcp-1.4.jar:1.4]
	at sun.reflect.GeneratedMethodAccessor55.invoke(Unknown Source) ~[na:na]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) ~[na:1.6.0_13]
	at java.lang.reflect.Method.invoke(Method.java:597) ~[na:1.6.0_13]
	at net.bull.javamelody.JdbcWrapper$ConnectionInvocationHandler.invoke(JdbcWrapper.java:185) ~[javamelody-1.49.0.jar:na]
	at net.bull.javamelody.JdbcWrapper$DelegatingInvocationHandler.invoke(JdbcWrapper.java:282) ~[javamelody-1.49.0.jar:na]
	at $Proxy36.setAutoCommit(Unknown Source) ~[na:na]
	at org.hibernate.transaction.JDBCTransaction.begin(JDBCTransaction.java:91) ~[hibernate-core-3.5.6-Final.jar:3.5.6-Final]
	at org.hibernate.impl.SessionImpl.beginTransaction(SessionImpl.java:1463) [hibernate-core-3.5.6-Final.jar:3.5.6-Final]
	at org.springframework.orm.hibernate3.HibernateTransactionManager.doBegin(HibernateTransactionManager.java:555) [spring-orm-3.1.1.RELEASE.jar:3.1.1.RELEASE]
	at org.springframework.transaction.support.AbstractPlatformTransactionManager.getTransaction(AbstractPlatformTransactionManager.java:371) [spring-tx-3.1.1.RELEASE.jar:3.1.1.RELEASE]
	at org.springframework.transaction.interceptor.TransactionAspectSupport.createTransactionIfNecessary(TransactionAspectSupport.java:335) [spring-tx-3.1.1.RELEASE.jar:3.1.1.RELEASE]
	at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:105) [spring-tx-3.1.1.RELEASE.jar:3.1.1.RELEASE]
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172) [spring-aop-3.1.1.RELEASE.jar:3.1.1.RELEASE]
	at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:202) [spring-aop-3.1.1.RELEASE.jar:3.1.1.RELEASE]
	at $Proxy72.findPageByORMSearch(Unknown Source) [na:na]

網上看到這兩個解決辦法。驗證中。

一是修改my.cnf： 

 

[ mysqld]  

wait_timeout=31536000  

interactive_timeout=31536000  

 

將過期時間修改為1年。 

 

二是在連接URL上添加參數：&autoReconnect=true&failOverReadOnly=false 

最終解決辦法：URL添加參數貌似不管用，我用的是mysql5.6，網上說這個5以前的版本才有效。所以只能使用改mysql配置的方法了。

上述問題是由mysql5數據庫的配置引起的。mysql5將其連接的等待時間(wait_timeout)缺省為8小時。在其客戶程序中可以這樣來查看其值： 

mysql﹥ 

mysql﹥ show global variables like 'wait_timeout'; 

+---------------+---------+ 

| Variable_name | Value | 

+---------------+---------+ 

| wait_timeout | 28800 | 

+---------------+---------+ 

1 row in set (0.00 sec) 


28800 seconds，也就是8小時。 

如果在wait_timeout秒期間內，數據庫連接(java.sql.Connection)一直處於等待狀態，mysql5就將該連接關閉。這時，你的Java應用的連接池仍然合法地持有該連接的引用。當用該連接來進行數據庫操作時，就碰到上述錯誤。這解釋了為什么我的程序第二天不能登錄 的問題。 



本人覺得最簡單的辦法，就是對症下葯：既然問題是由mysql5的全局變量wait_timeout的缺省值太小引起的，我們將其改大就好了。 

查看mysql5的手冊，發現對wait_timeout的最大值分別是24天/365天(windows/linux)。以windows為 例，假設我們要將其設為21天，我們只要修改mysql5的配置文件“my.ini”(mysql5 installation dir)，增加一行：wait_timeout=1814400

需要重新啟動mysql5。 

linux系統配置文件：/etc/my.cnf 

測試顯示問題解決了。