jsp学习笔记（一）

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) {}          }        }    }