MySQL之—重连，连接丢失的代码实例详解

最近，项目中经常遇到mysql重连，连接丢失的代码的问题，研究了下解决方法，现共享出来，大家可以参考一下，下面我们就进入正题。

1、错误日志

Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: 
The last packet successfully received from the server was 20,820,001 milliseconds ago.  
The last packe
t sent successfully to the server was 20,820,002 milliseconds ago. is longer than the server configured value of 'wait_timeout'. 
You should consider either expiring and/or testing connection validity before use in your application, 
increasing the server configured values for client timeouts, or using the Connector/J connection property 'autoReconnect=true' to avoid this problem.
            at sun.reflect.GeneratedConstructorAccessor29.newInstance(Unknown Source) ~[na:na]
            at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.7.0_51]
            at java.lang.reflect.Constructor.newInstance(Constructor.java:526) ~[na:1.7.0_51]
            at com.mysql.jdbc.Util.handleNewInstance(Util.java:411) ~[mysql-connector-java-5.1.29.jar:na]
            at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1129) ~[mysql-connector-java-5.1.29.jar:na]
            at com.mysql.jdbc.MysqlIO.send(MysqlIO.java:3988) ~[mysql-connector-java-5.1.29.jar:na]
            at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2598) ~[mysql-connector-java-5.1.29.jar:na]
            at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2778) ~[mysql-connector-java-5.1.29.jar:na]
            at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2828) ~[mysql-connector-java-5.1.29.jar:na]
            at com.mysql.jdbc.ConnectionImpl.setAutoCommit(ConnectionImpl.java:5372) ~[mysql-connector-java-5.1.29.jar:na]
            at com.mchange.v2.c3p0.impl.NewProxyConnection.setAutoCommit(NewProxyConnection.java:881) ~[c3p0-0.9.1.1.jar:0.9.1.1]
            at org.quartz.impl.jdbcjobstore.AttributeRestoringConnectionInvocationHandler.setAutoCommit(AttributeRestoringConnectionInvocationHandler.java:98) 
            ~[quartz-2.2.1.jar:na]

2、解决办法

- 如果使用的是JDBC，在JDBC URL上添加?autoReconnect=true，如：

jdbc:mysql://127.0.0.1:3306/mydb?autoReconnect=true

- 如果是在Spring中使用DBCP连接池，在定义datasource增加属性validationQuery和testOnBorrow，如：

- 如果是在Spring中使用c3p0连接池，则在定义datasource的时候，添加属性testConnectionOnCheckin和testConnectionOnCheckout，如：