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 driver at 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.NullPointerException at 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！