<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
	
	<bean id="datasource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
		<property name="user" value="root"></property>
		<property name="password" value="***"></property>
		<property name="jdbcUrl" value="jdbc:mysql://localhost:3306/mqtt"></property>
		<property name="driverClass" value="com.mysql.jdbc.Driver"></property>
	</bean>

</beans>

public static void main(String[] args) throws BeansException, SQLException {
	String fileName = "ioc2.xml";
	ApplicationContext context = new ClassPathXmlApplicationContext(fileName);
	DataSource datasource =  (DataSource) context.getBean("datasource");
//		System.out.println(datasource.getConnection());
	Connection connection = datasource.getConnection();
	Statement statement = connection.createStatement();
	ResultSet resultSet = statement.executeQuery("select *  from user");
	while (resultSet.next()) {
		int userid = resultSet.getInt("userid");
		System.out.println(userid);
	}
}

<context:property-placeholder location="classpath:jdbc.properties"/>