Spring is losing connection to the DB and does not recover or reconnect

Per a senior member in the Spring forums, the Spring DataSource is not intended for production use:

The above answers are only part of the solution. Indeed you need proper transaction managent AND you need a connection pool. The DriverManagerDataSource is NOT meant for production, it opens and closes a datebase connection each time it needs one.

Instead you can use C3P0 as your DataSource which handles the reconnect and is much better in performance. Here's a quick example of a potential configuration in a Spring xml configuration:

<bean id="c3p0DataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"    destroy-method="close">    <property name="driverClass" value="com.mysql.jdbc.Driver" />    <property name="jdbcUrl" value="#{systemProperties.dbhost}" />    <property name="user" value="#{systemProperties.dbuser}" />    <property name="password" value="#{systemProperties.dbpass}" />    <property name="maxPoolSize" value="25" />    <property name="minPoolSize" value="10" />    <property name="maxStatements" value="100" />    <property name="testConnectionOnCheckout" value="true" /></bean><bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">    <constructor-arg ref="c3p0DataSource" /></bean>

Spring (3) boot settings for hibernate and oracle:

spring.datasource.test-on-borrow=true

spring.datasource.validation-query=select 1 from dual

Try changing your connection URL to:

spring.datasource.url=jdbc:mysql://localhost/validation?autoReconnect=true