src\dayday\conn.java

package dayday; import java.sql.Connection; import java.sql.DriverManager; import java.sql.SQLException; /**  * Created by I am master on 2016/11/29.  */ public class conn {
      private String user;     private String password;     private String driveClass;     private String jdbcUrl;     private Connection connection;     public void setUser(String user){
          this.user=user;     }     public void setPassword(String password){
          this.password=password;     }     public void setDriveClass(String driveClass){
          this.driveClass=driveClass;     }     public void setJdbcUrl(String jdbcUrl){
          this.jdbcUrl=jdbcUrl;     }     public Connection getConnection() throws SQLException, ClassNotFoundException {
          Class.forName(driveClass);         connection= DriverManager.getConnection(jdbcUrl,user,password);         return connection;     } }

src\dayday\Main.java

package dayday; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; import java.net.SocketTimeoutException; import java.sql.SQLException; /**  * Created by I am master on 2016/11/28.  */ public class Main {
      public static void main(String[] args) throws SQLException, ClassNotFoundException {
         ApplicationContext ctx=new ClassPathXmlApplicationContext("beans.xml");        conn con=ctx.getBean("conn",conn.class);         System.out.println(con.getConnection());     } }

src\db.properties

src\beans.xml

     
         
           
          
          
          
              
               
               
               
           
      
     运行结果： com.mysql.jdbc.JDBC4Connection@17942a1

通过
    加入外部配置文件

通过${var}引用外部的属性