配置文件相关

dataSource=com.mchange.v2.c3p0.ComboPooledDataSource  
driverClass=com.mysql.jdbc.Driver  
jdbcUrl=jdbc:mysql://localhost:3306/shop 
username=root  
password=root  

 <context:property-placeholder location="classpath:conn.properties"/><!-- 加载配置文件 -->  
  
 <!-- com.mchange.v2.c3p0.ComboPooledDataSource类在c3p0-0.9.5.1.jar包的com.mchange.v2.c3p0包中 -->  
 <bean id="dataSource" class="${dataSource}"> <!-- 这些配置Spring在启动时会去conn.properties中找 -->  
    <property name="driverClass" value="${driverClass}" />  
    <property name="jdbcUrl" value="${jdbcUrl}" />  
    <property name="user" value="${user}" />  
    <property name="password" value="${password}" />  
 </bean> 

    @Value("${shop.url}")
    private String url;

@Configuration
@PropertySource("classpath:jdbc.properties")
//@ConfigurationProperties(prefix = "demo")使用这个可以省略@value
public class JdbcConfig{
    @Value("jdbcUrl")
    String jdbcUrl;
    @Value("driverClass")
    String driverClass;
    @Value("user")
    String user;
    @Value("password")
    String password

    @DataSource
    public DataSource dataSource(){
         DruidDataSource dataSource = new DruidDataSource();
         dataSource.setDrieverClassName(driverClass);
         dataSource.setUrl(jdbcUrl);
         dataSource.setUserName(user);
         dataSource.setPassword(password);
         return dataSource;
    }
}