package DAO;
    import java.sql.Connection; 
    import java.sql.ResultSet;
    import java.sql.Statement;
    import java.sql.SQLException;
    import javax.naming.Context; 
    import javax.naming.InitialContext; 
    import javax.naming.NamingException;
    import javax.sql.DataSource;
    public class DAOConnection { 
        private static DataSource ds = null;
        public static DataSource getDataSource() throws Exception{
            long start = System.currentTimeMillis();
            if (ds == null) {
              Context initContext = new InitialContext(); //初始化
              if (initContext == null) throw new Exception("No Context"); 
              Context envContext = (Context) initContext.lookup("java:/comp/env"); 
              ds = (DataSource) envContext.lookup("jdbc/BookDb"); 
              //需要与context里的       目录一致
              long end = System.currentTimeMillis();
              System.out.println(end-start);             //测试连接数据库时间
            }
            return ds;[/i]
        }
        public static Connection getConnection() { 
          try { 
            Connection conn = getDataSource().getConnection();
            if (conn != null) return conn; 
          } catch (Exception e){ e.printStackTrace(); } 
            return null; 
        } 
        public static void close(Connection conn, Statement st ,ResultSet rs) {
          if (rs != null) {
            try {
              rs.close();
            } catch (SQLException ex) {}
          }
          if (st != null) {
            try {
               st.close();
            } catch (SQLException ex) {}
          }
 
          if (conn != null) {
            try {
              conn.close();
            } catch (Exception ex) {}
          }
        }
    }