It is okay if you are in development phase. When deploy project using hibernate and mysql to server, you may get an error throw:

Detailed

 Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: No operations allowed after connection closed.Connection was implicitly closed by the driver.
      at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
      at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
      at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
      at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
      at com.mysql.jdbc.Util.handleNewInstance(Util.java:409)
      at com.mysql.jdbc.Util.getInstance(Util.java:384)
      at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1015)
      at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:989)
      at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:984)
      at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:929)
      at com.mysql.jdbc.ConnectionImpl.throwConnectionClosedException(ConnectionImpl.java:1193)
      at com.mysql.jdbc.ConnectionImpl.checkClosed(ConnectionImpl.java:1180)
      at com.mysql.jdbc.ConnectionImpl.prepareStatement(ConnectionImpl.java:4137)
      at com.mysql.jdbc.ConnectionImpl.prepareStatement(ConnectionImpl.java:4103)
      at org.hibernate.jdbc.AbstractBatcher.getPreparedStatement(AbstractBatcher.java:505)
      at org.hibernate.jdbc.AbstractBatcher.getPreparedStatement(AbstractBatcher.java:423)
      at org.hibernate.jdbc.AbstractBatcher.prepareQueryStatement(AbstractBatcher.java:139)
      at org.hibernate.loader.Loader.prepareQueryStatement(Loader.java:1547)
      at org.hibernate.loader.Loader.doQuery(Loader.java:673)
      at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:236)
      at org.hibernate.loader.Loader.doList(Loader.java:2220)
      ... 36 more
Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: The last packet successfully received from the server was 34,247,052 milliseconds ago.  The last packet sent successfully to the server was 34,247,052 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.NativeConstructorAccessorImpl.newInstance0(Native Method)
      at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
      at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
      at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
      at com.mysql.jdbc.Util.handleNewInstance(Util.java:409)
      at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1118)
      at com.mysql.jdbc.MysqlIO.send(MysqlIO.java:3321)
      at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1940)
      at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2113)
      at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2568)
      at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2113)
      at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:2275)
      at org.hibernate.jdbc.AbstractBatcher.getResultSet(AbstractBatcher.java:186)
      at org.hibernate.loader.Loader.getResultSet(Loader.java:1787)
      at org.hibernate.loader.Loader.doQuery(Loader.java:674)
      at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:236)
      at org.hibernate.loader.Loader.doList(Loader.java:2220)
      at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2104)
      at org.hibernate.loader.Loader.list(Loader.java:2099)
      at org.hibernate.loader.criteria.CriteriaLoader.list(CriteriaLoader.java:94)
      at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1569)
      at org.hibernate.impl.CriteriaImpl.list(CriteriaImpl.java:283)
      at com.xyz.abc.DAO.GenericHibernateDAO.findByField(GenericHibernateDAO.java:119)
      at com.xyz.abc.DAO.JobDAO.getJobsByLdap(JobDAO.java:115)
      at com.xyz.abc.business.Jcr.getMyruns(Jcr.java:272)
      at com.xyz.abc.business.abcService.getMyruns(abcService.java:54)
      at sun.reflect.GeneratedMethodAccessor139.invoke(Unknown Source)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
      at java.lang.reflect.Method.invoke(Method.java:597)
      at org.apache.axis2.rpc.receivers.RPCUtil.invokeServiceClass(RPCUtil.java:194)
      at org.apache.axis2.rpc.receivers.RPCMessageReceiver.invokeBusinessLogic(RPCMessageReceiver.java:102)
      at org.apache.axis2.receivers.AbstractInOutMessageReceiver.invokeBusinessLogic(AbstractInOutMessageReceiver.java:40)
      at org.apache.axis2.receivers.AbstractMessageReceiver.receive(AbstractMessageReceiver.java:114)
      at org.apache.axis2.engine.AxisEngine.receive(AxisEngine.java:173)
      at org.apache.axis2.transport.http.HTTPTransportUtils.processHTTPPostRequest(HTTPTransportUtils.java:173)
      at org.apache.axis2.transport.http.AxisServlet.doPost(AxisServlet.java:142)
      at javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
      at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304)
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
      at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:240)
      at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:203)
      at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164)
      at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:108)
      at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
      at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:379)
      at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:242)
      at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:259)
      at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:237)
      ... 4 more
Caused by: java.net.SocketException: Software caused connection abort: socket write error

To resolve this problem, you just set property autoReconnect = true

MySQL Connection URL

You can set value in the connection URL in parameters:

jdbc.url=jdbc:mysql://ipaddress:3306/database?autoReconnect=true&autoReconnectForPools=true

Hibernate Configuration File

Add the following attributes to file hibernate.cfg.xml

<property name="connection.autoReconnect">true</property>
<property name="connection.autoReconnectForPools">true</property> 
<property name="connection.is-connection-validation-required">true</property>

C3P0 Connection Pool

In our project, it is configured as follows

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" 
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>
        <property name="hibernate.bytecode.use_reflection_optimizer">false</property>
        <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="hibernate.connection.username">test</property>
        <property name="hibernate.connection.password">test</property>
        <property name="hibernate.connection.url">jdbc:mysql://xmpp.nms.ssdc:3306/joomla?autoReconnect=true&amp;autoReconnectForPools=true</property>
        <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>

        <!--Connection Pooling-->
        <property name="c3p0.validate">true</property>
        <property name="c3p0.min_size">10</property>
        <property name="c3p0.max_size">600</property>
        <property name="c3p0.timeout">1800</property> <!-- seconds --> 
        <property name="c3p0.max_statements">50</property>
        <property name="c3p0.preferredTestQuery">SELECT 1;</property>
        <property name="c3p0.testConnectionOnCheckout">true</property>
        <property name="c3p0.idle_test_period">3000</property> <!-- seconds --> 
    
        <property name="connection.provider_class">org.hibernate.c3p0.internal.C3P0ConnectionProvider</property>
        <property name="connection.autoReconnect">true</property>
        <property name="connection.autoReconnectForPools">true</property>
        <property name="connection.is-connection-validation-required">true</property>
    
        <property name="show_sql">true</property>
        <mapping resource="vn/vnpttech/ssdc/nms/xmpp/model/Rosterusers.hbm.xml"/>
        <mapping resource="vn/vnpttech/ssdc/nms/xmpp/model/Users.hbm.xml"/>
    </session-factory>
</hibernate-configuration>

When deploy application we must include the following libraries:

Or, with maven dependency:

<!-- Connection Pooling -->
<dependency>
	<groupId>com.mchange</groupId>
	<artifactId>c3p0</artifactId>
	<version>0.9.5.1</version> 
</dependency> 
<dependency>
	<groupId>org.hibernate</groupId>
	<artifactId>hibernate-c3p0</artifactId>
	<version>5.0.0.CR1</version> 
	<exclusions>
		<exclusion>
			<artifactId>c3p0</artifactId>
			<groupId>com.mchange</groupId>
		</exclusion>
	</exclusions>
</dependency>

Reference Link