JDBC 你应该知道的事

JDBC你应该知道的事？

/* * 文 件 名:  DbUtils.java * 版    权:  Co., Ltd. Copyright YYYY-YYYY,  All rights reserved * 描    述:  <描述> * 修 改 人:   * 修改时间:  Apr 19, 2013 * 跟踪单号:  <跟踪单号> * 修改单号:  <修改单号> * 修改内容:  <修改内容> */package com.huawei.jdbc;import java.sql.Connection;import java.sql.DriverManager;import java.sql.ResultSet;import java.sql.SQLException;import java.sql.Statement;/** * <一句话功能简述> * <功能详细描述> *  * @author   * @version  [版本号, Apr 19, 2013] * @see  [相关类/方法] * @since  [产品/模块版本] */public class DbUtils{    private static DbUtils dbUtils = new DbUtils();        private DbUtils()    {            }        public static DbUtils getInstance()    {        return dbUtils;    }        public void queryExcute()    {                Connection conn = null;        Statement stm = null;        ResultSet result = null;        try        {            Class.forName("oracle.jdbc.driver.OracleDriver");        }        catch (ClassNotFoundException e)        {            e.printStackTrace();        }        try        {            conn = DriverManager.getConnection("jdbc:oracle:thin:@10.137.107.160:1521:iptvmem",                    "userdb30",                    "I_Vcbs33");                        stm = conn.createStatement();                        String sql = "select * from ocs_tasktodo2 o where o.subscriberno ='"                    + "826670842" + "'";                        result = stm.executeQuery(sql);                        if (null != result)            {                while (result.next())                {                    System.out.println(result.getString("subscriberno"));                }            }                    }        catch (SQLException e)        {            e.printStackTrace();        }        finally        {            try            {                result.close();                stm.close();                conn.close();            }            catch (SQLException e)            {                e.printStackTrace();            }        }            }}

哈哈，我知道的就这么多，懂一点补充一点

        try        {            Class.forName("oracle.jdbc.driver.OracleDriver");        }        catch (ClassNotFoundException e)        {            e.printStackTrace();        }

这一行没有任何的设值，孤独的立在代码中，有点奇怪，于是我删掉了这一行。再跑一边，哈哈报错了

java.sql.SQLException: No suitable driverat java.sql.DriverManager.getConnection(DriverManager.java:545)at java.sql.DriverManager.getConnection(DriverManager.java:171)at com.huawei.jdbc.DbUtils.queryExcute(DbUtils.java:59)at com.huawei.jdbc.DbUtils.main(DbUtils.java:40)Exception in thread "main" java.lang.NullPointerExceptionat com.huawei.jdbc.DbUtils.queryExcute(DbUtils.java:87)at com.huawei.jdbc.DbUtils.main(DbUtils.java:40)

猜测这个是给jvm申明一个Oracle驱动的实例。

 

再接着

conn = DriverManager.getConnection("jdbc:oracle:thin:@10.137.107.160:1521:iptvmem",                    "userdb30",                    "I_Vcbs33");

使用DriverManager建立了一个连接，可以看下其中的方法

    public static synchronized Connection getConnection(String url, String user, String password) throws SQLException {        java.util.Properties info = new java.util.Properties();        // Gets the classloader of the code that called this method, may // be null.ClassLoader callerCL = DriverManager.getCallerClassLoader();if (user != null) {    info.put("user", user);}if (password != null) {    info.put("password", password);}        return (getConnection(url, info, callerCL));    }

再接下来就是：

            stm = conn.createStatement();                        String sql = "select * from ocs_tasktodo2 o where o.subscriberno ='"                    + "826670842" + "'";                        result = stm.executeQuery(sql);                        if (null != result)            {                while (result.next())                {                    System.out.println(result.getString("subscriberno"));                }            }

 

请大神解释一下，从上至下的流程！