数据源点滴

 

 

以前写程序时，都是用java自带的DriverManager类进行驱动，学习了DataSource后，才知道它的不足，但是，如果没接触过java.sql包提供的DriverManager，是体会不到DataSource的优点的，DataSource具有以下优点：首先，驱动程序类可以不硬编码在应用程序中，其次，当数据或驱动程序发生更改时，不必更改应用程序，也就是可以对数据源的属性进行修改，第三，可获得连接池和分布式事务，这是用DriverManager建立的连接所做不到的！总结一下用不同DataSource连接数据库的方法，尽管方法很多，但是基本思想和代码的写法都是大同小异，你可以根据需求选择最适合的，而不是挑最时髦的！

１commons.dbcp.BasicDataSource：

import org.apache.commons.dbcp.BasicDataSource;

import org.apache.commons.logging.Log;

import org.apache.commons.logging.LogFactory;

import org.apache.log4j.BasicConfigurator;

 

import java.sql.Connection;

import java.sql.PreparedStatement;

import java.sql.ResultSet;

import java.sql.SQLException;

 

 

public class DsDemo {

 

       /**

        * @param args

        */

      

       public static void main(String[] args)

       {

              // TODO 自动生成方法存根

              BasicConfigurator.configure();

              Log log = LogFactory.getLog(DsDemo.class);

             

              Connection conn = null;

              PreparedStatement pstmt = null;

              ResultSet rs = null;

             

              BasicDataSource ds = new BasicDataSource();

              ds.setDriverClassName("com.microsoft.sqlserver.jdbc.SQLServerDriver");

              ds.setUrl("jdbc:sqlserver://localhost;databaseName=UserL");

              ds.setUsername("chen");

              ds.setPassword("chen");

             

                     try {

                            conn = ds.getConnection();

                     } catch (SQLException e1) {

                            // TODO 自动生成 catch 块

                            log.error("无法建立连接");

                     }

                     try {

                            pstmt = conn.prepareStatement("select * from users");

                     } catch (SQLException e1) {

                            // TODO 自动生成 catch 块

                            log.error("执行语句时出错");

                     }

                     try {

                            rs = pstmt.executeQuery();

                     } catch (SQLException e1) {

                            // TODO 自动生成 catch 块

                            log.error("产生记录集时出错！");

                     }

                     try {

                            while(rs.next())

                            {

                                   log.info(rs.getString("name"));

                            }

                     } catch (SQLException e1) {

                            // TODO 自动生成 catch 块

                            log.error("记录集无法显示");

                     }

             

              finally

              {

                     if(rs!=null)

                     {

                            try {

                                   rs.close();

                            } catch (SQLException e) {

                                   // TODO 自动生成 catch 块

                                   log.error("无法关闭记录集");

                            }

                            rs = null;

                     }

                     if(pstmt != null)

                     {

                            try {

                                   pstmt.close();

                            } catch (SQLException e) {

                                   // TODO 自动生成 catch 块

                                   log.error("无法关闭Statement");

                            }

                            pstmt = null;

                     }

                     if(conn != null)

                     {

                            try {

                                   conn.close();

                            } catch (SQLException e) {

                                   // TODO 自动生成 catch 块

                                   log.error("无法关闭连接");

                            }

                            conn = null;

                     }

              }

 

       }

 

}

这是个完整的程序，只要你有相应的jar包，这个小程序跑通是没什么问题的，当然，这只是初学者的练习而已！

２org.springframework.jdbc.datasource.DriverManagerDataSource

import java.sql.Connection;

import java.sql.PreparedStatement;

import java.sql.ResultSet;

import java.sql.SQLException;

 

import org.apache.commons.logging.Log;

import org.apache.commons.logging.LogFactory;

import org.apache.log4j.BasicConfigurator;

import org.springframework.context.ApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

 

import org.springframework.jdbc.datasource.DriverManagerDataSource;

 

public class SpringDmds {

 

       /**

        * @param args

        */

      

       DriverManagerDataSource dataSource = null;

       Connection conn = null;

       PreparedStatement psmtm = null;

       ResultSet rs = null;

       public void setDataSource(DriverManagerDataSource dataSource)

       {

              this.dataSource = dataSource;

       }

       public void getAllInfo()

       {

             

              BasicConfigurator.configure();

              Log log = LogFactory.getLog(SpringDmds.class);

              try {

                     conn = dataSource.getConnection();

              } catch (SQLException e) {

                     // TODO 自动生成 catch 块

                     log.error("得到数据源时出错！");

              }

              try {

                     psmtm = conn.prepareStatement("select * from users");

              } catch (SQLException e) {

                     // TODO 自动生成 catch 块

                     log.error("sql语句出错");

              }

              try {

                     rs = psmtm.executeQuery();

              } catch (SQLException e) {

                     // TODO 自动生成 catch 块

                     log.error("得到记录集时出错");

              }

              try {

                     while(rs.next())

                     {

                            log.info(rs.getString("name"));

                     }

              } catch (SQLException e) {

                     // TODO 自动生成 catch 块

                     log.error("读取数据库时出错");

              }

              finally

              {

                     if(rs!=null)

                     {

                            try {

                                   rs.close();

                            } catch (SQLException e) {

                                   // TODO 自动生成 catch 块

                                   log.error("记录集无法关闭");

                            }

                            rs=null;

                     }

                     if(psmtm!=null)

                     {

                            try {

                                   psmtm.close();

                            } catch (SQLException e) {

                                   // TODO 自动生成 catch 块

                                   log.error("statment无法关闭");

                            }

                            psmtm=null;

                     }

                     if(conn!=null)

                     {

                            try {

                                   conn.close();

                            } catch (SQLException e) {

                                   // TODO 自动生成 catch 块

                                   log.error("无法关闭连接");

                            }

                            conn=null;

                     }

              }

             

       }

       public static void main(String[] args)

       {

              // TODO 自动生成方法存根

              ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");

              SpringDmds sd = (SpringDmds)context.getBean("springprop");

              sd.getAllInfo();

 

       }

 

}

相信高手一看就能就明白，这是Spring提供的一个只供测试用的DataSource类，只是自己做练习时用一下，在项目中千万不能把它搬出来！当然，这个程序还需要在Spring中装配，代码很简单的！

今天只是介绍了一些简单的，由第三方提供的用来得到DataSource的方法，除了这些，还有一些更有实力的，用来得到DataSource的框架，比如ibatis, hibernate-3.1等都为用户提供了很多数据源，所以我们作为开发人员是幸运的！

关于ibatis和 hibernate-3.1的用法下次介绍！