Jsp+Servlet实现文件上传下载 文件列表展示（二）(2/3)

package util; 

import java.sql.*; 
import java.io.InputStream; 
import java.util.Properties; 

/** 
 * 数据库工具类 
 * 
 * @author xusucheng 
 * @create 2017-11-18 
 **/ 
public class DBUtil { 
 //定义链接所需要的变量 
 private static Connection con = null; 
 private static PreparedStatement ps = null; 
 private static ResultSet rs = null; 

 //定义链接数据库所需要的参数 
 private static String url = ""; 
 private static String username = ""; 
 private static String driver=""; 
 private static String password=""; 

 //定义读取配置文件所需要的变量 
 private static Properties pp = null; 
 private static InputStream fis = null; 

 /** 
  * 加载驱动 
  */ 
 static { 
  try { 
   //从dbinfo.properties配置文件中读取配置信息 
   pp = new Properties(); 
   fis = DBUtil.class.getClassLoader().getResourceAsStream("db.properties"); 

   pp.load(fis); 
   url = pp.getProperty("url"); 
   username = pp.getProperty("username"); 
   driver=pp.getProperty("driver"); 
   password=pp.getProperty("password"); 

   //加载驱动 
   Class.forName(driver); 

  } catch (Exception e) { 
   System.out.println("驱动加载失败！"); 
   e.printStackTrace(); 
  } finally { 
   try { 
    fis.close(); 
   } catch (Exception e) { 
    e.printStackTrace(); 
   } 

   fis = null; //垃圾回收自动处理 
  } 

 } 

 /** 
  * 得到Connection链接 
  * @return Connection 
  */ 
 public static Connection getConnection() { 

  try { 
   //建立连接 
   con = DriverManager.getConnection(url, username, password); 

  } catch (Exception e) { 
   System.out.println("数据库链接失败！"); 
   e.printStackTrace(); 
  } 

  return con; 
 } 

 /*public DBUtil(String sql){ 
  try { 
   ps = getConnection().prepareStatement(sql);//准备执行语句 
  } catch (Exception e) { 
   e.printStackTrace(); 
  } 
 } 

 public void close() { 
  try { 
   con.close(); 
   ps.close(); 
  } catch (SQLException e) { 
   e.printStackTrace(); 
  } 
 }*/ 

 /** 
  * 统一的资源关闭函数 
  * @param rs 
  * @param ps 
  * @param con 
  */ 
 public static void close(ResultSet rs,Statement ps, Connection con){ 

  if(rs != null) { 
   try { 
    rs.close(); 
   } catch (Exception e) { 
    e.printStackTrace(); 
   } 
  } 
  if(ps != null) { 
   try { 
    ps.close(); 
   } catch (Exception e) { 
    e.printStackTrace(); 
   } 
  } 
  if(con != null) { 
   try { 
    con.close(); 
   } catch (Exception e) { 
    e.printStackTrace(); 
   } 
  } 
 } 

} 

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