The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.，,The last pac

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.，,The last pac

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.        at org.springframework.jdbc.support.JdbcUtils.extractDatabaseMetaData(JdbcUtils.java:296) ~[spring-jdbc-3.1.2.RELEASE.jar:3.1.2.RELEASE]        at org.springframework.jdbc.support.JdbcUtils.extractDatabaseMetaData(JdbcUtils.java:320) ~[spring-jdbc-3.1.2.RELEASE.jar:3.1.2.RELEASE]        at org.springframework.jdbc.support.SQLErrorCodesFactory.getErrorCodes(SQLErrorCodesFactory.java:214) ~[spring-jdbc-3.1.2.RELEASE.jar:3.1.2.RELEASE]        at org.springframework.jdbc.support.SQLErrorCodeSQLExceptionTranslator.setDataSource(SQLErrorCodeSQLExceptionTranslator.java:141) [spring-jdbc-3.1.2.RELEASE.jar:3.1.2.RELEASE]        at org.springframework.jdbc.support.SQLErrorCodeSQLExceptionTranslator.<init>(SQLErrorCodeSQLExceptionTranslator.java:104) [spring-jdbc-3.1.2.RELEASE.jar:3.1.2.RELEASE]        at org.springframework.jdbc.support.JdbcAccessor.getExceptionTranslator(JdbcAccessor.java:99) [spring-jdbc-3.1.2.RELEASE.jar:3.1.2.RELEASE]        at org.springframework.orm.ibatis.SqlMapClientTemplate.execute(SqlMapClientTemplate.java:203) [spring-orm-3.1.2.RELEASE.jar:3.1.2.RELEASE]        at org.springframework.orm.ibatis.SqlMapClientTemplate.queryForList(SqlMapClientTemplate.java:293) [spring-orm-3.1.2.RELEASE.jar:3.1.2.RELEASE]        at com.panguso.radar.dao.PublicSentimentDao.getPublicSentimentListByAlarmSettings(PublicSentimentDao.java:99) [radar-core-0.0.1-SNAPSHOT.jar:0.0.1-SNAPSHOT]        at com.panguso.radar.service.PublicSentimentService.getPublicSentmentsByAlarmSetting(PublicSentimentService.java:158) [radar-core-0.0.1-SNAPSHOT.jar:0.0.1-SNAPSHOT]        at com.panguso.radar.async.AlarmThread.doTask(AlarmThread.java:105) [radar-alarm-0.0.1-SNAPSHOT.jar:0.0.1-SNAPSHOT]        at com.panguso.radar.async.SafeStopThread.run(SafeStopThread.java:48) [radar-core-0.0.1-SNAPSHOT.jar:0.0.1-SNAPSHOT]Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failureThe last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.6.0_20]        at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39) ~[na:1.6.0_20]        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27) ~[na:1.6.0_20]        at java.lang.reflect.Constructor.newInstance(Constructor.java:513) ~[na:1.6.0_20]        at com.mysql.jdbc.Util.handleNewInstance(Util.java:411) ~[mysql-connector-java-5.1.20.jar:na]        at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1116) ~[mysql-connector-java-5.1.20.jar:na]        at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:348) ~[mysql-connector-java-5.1.20.jar:na]        at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2391) ~[mysql-connector-java-5.1.20.jar:na]        at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2428) ~[mysql-connector-java-5.1.20.jar:na]        at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2213) ~[mysql-connector-java-5.1.20.jar:na]        at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:797) ~[mysql-connector-java-5.1.20.jar:na]        at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47) ~[mysql-connector-java-5.1.20.jar:na]        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.6.0_20]        at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39) ~[na:1.6.0_20]        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27) ~[na:1.6.0_20]        at java.lang.reflect.Constructor.newInstance(Constructor.java:513) ~[na:1.6.0_20]        at com.mysql.jdbc.Util.handleNewInstance(Util.java:411) ~[mysql-connector-java-5.1.20.jar:na]        at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:389) ~[mysql-connector-java-5.1.20.jar:na]        at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:305) ~[mysql-connector-java-5.1.20.jar:na]        at org.apache.commons.dbcp.DriverConnectionFactory.createConnection(DriverConnectionFactory.java:38) ~[commons-dbcp-1.4.jar:1.4]        at org.apache.commons.dbcp.PoolableConnectionFactory.makeObject(PoolableConnectionFactory.java:582) ~[commons-dbcp-1.4.jar:1.4]        at org.apache.commons.pool.impl.GenericObjectPool.borrowObject(GenericObjectPool.java:1148) ~[commons-pool-1.5.4.jar:1.5.4]        at org.apache.commons.dbcp.PoolingDataSource.getConnection(PoolingDataSource.java:106) ~[commons-dbcp-1.4.jar:1.4]        at org.apache.commons.dbcp.BasicDataSource.getConnection(BasicDataSource.java:1044) ~[commons-dbcp-1.4.jar:1.4]        at org.springframework.jdbc.datasource.DataSourceUtils.doGetConnection(DataSourceUtils.java:111) ~[spring-jdbc-3.1.2.RELEASE.jar:3.1.2.RELEASE]        at org.springframework.jdbc.datasource.TransactionAwareDataSourceProxy$TransactionAwareInvocationHandler.invoke(TransactionAwareDataSourceProxy.java:224) ~[spring-jdbc-3.1.2.RELEASE.jar:3.1.2.RELEASE]

测试程序发现这样的异常，从网上查到原因如下：

使用Connector/J连接MySQL数据库，程序运行较长时间后就会报以下错误：

Communications link failure，The last packet successfully received from the server was millisecond ago.The last packet successfully sent to the server was millisecond ago。

其中错误还会提示你修改wait_timeout或是使用Connector/J的autoReconnect属性避免该错误。(我的错误没有这样的提示）后来查了一些资料，才发现遇到这个问题的人还真不少，大部分都是使用连接池方式时才会出现这个问题，短连接应该很难出现这个问题。这个问题的原因：

MySQL服务器默认的“wait_timeout”是28800秒即8小时，意味着如果一个连接的空闲时间超过8个小时，MySQL将自动断开该连接，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。

1.按照错误的提示，可以在JDBC URL中使用autoReconnect属性，实际测试时使用了

autoReconnect=true&failOverReadOnly=false，不过并未起作用，使用的是5.1版本，可能真像网上所说的只对4之前的版本有效。

2.没办法，只能修改MySQL的参数了，wait_timeout最大为31536000即1年，在my.cnf中加入：

[mysqld]wait_timeout=31536000interactive_timeout=31536000

重启生效，需要同时修改这两个参数。

还有评论说：从某个地方看到.timeout最多是2147483（24天）吧,就算设置了大于这个数,也是按照这个来算的。

虽然报了这个异常，我的程序还是照常工作，这个也许是mysql的bug吧！哎！郁闷！怕以后不知道会不会影响我的应用，这几天发现了2个mysql的bug了。