MySQL - reconnection, detailed explanation of code examples for lost connections

Recently, I often encounter the problem of MySQL reconnection and lost connection code in the project. I have studied the solution and now share it for your reference. Now we will get to the point.

1. Error log

Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: 
The last packet successfully received from the server was 20,820,001 milliseconds ago.  
The last packet 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. Solution

- If you are using JDBC, on the JDBC URL Add ?autoReconnect=true, such as:

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

- If you use DBCP connection pool in Spring, add attributes validationQuery and testOnBorrow in the definition of datasource, such as:

<bean id="vrsRankDataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
    <property name="driverClassName" value="${jdbc.driverClassName}" />
    <property name="url" value="${countNew.jdbc.url}" />
    <property name="username" value="${countNew.jdbc.user}" />
    <property name="password" value="${countNew.jdbc.pwd}" />
    <property name="validationQuery" value="SELECT 1" />
    <property name="testOnBorrow" value="true"/>
</bean>

- If you use the c3p0 connection pool in Spring, add the attributes testConnectionOnCheckin and testConnectionOnCheckout when defining the datasource, such as:

<bean name="cacheCloudDB" class="com.mchange.v2.c3p0.ComboPooledDataSource">
    <property name="driverClass" value="${jdbc.driver}"/>
    <property name="jdbcUrl" value="${cache.url}"/>
    <property name="user" value="${cache.user}"/>
    <property name="password" value="${cache.password}"/>
    <property name="initialPoolSize" value="10"/>
    <property name="maxPoolSize" value="${cache.maxPoolSize}"/>
    <property name="testConnectionOnCheckin" value="false"/>
    <property name="testConnectionOnCheckout" value="true"/>
    <property name="preferredTestQuery" value="SELECT 1"/>
</bean>

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