JDBC(java Datebase Connector)
jdbc驱动程序
四种类型：
jdbc-odbc桥接驱动程序
Native-API
JDBC-Net
Native-Protocol (常见)
public class DBToolOld
{
public static void main(String[] args)
{
// 1、注册驱动
// DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver());
// new驱动类的时候会注册一份，DriverManager.registerDriver又会去注册一份驱动
// 硬编码在类中，不方便修改
// System.setProperty("driver", "oracle.jdbc.driver.OracleDriver");
// 因为key和value都是字符串，可以改到配置文件中
// 需要约定好key的值，注册起来不太方便
try
{
Class.forName("oracle.jdbc.driver.OracleDriver");
// 2、获得连接对象
String oracleUrl = "jdbc:oracle:thin:@192.168.6.100:1521:NIIT";
Connection conn = DriverManager.getConnection(oracleUrl, "scott",
"tiger");
// 3、开始执行SQL语句，先创建Statement对象
Statement stmt = conn.createStatement();
// 4、执行SQL语句，返回一个结果集，只有是SELECT语句、executeQuery才会返回结果集
ResultSet rs = stmt
.executeQuery("SELECT empNo, ename, hireDate, sal FROM Emp");
// 5、处理结果集
while (rs.next())
{
int empNo = rs.getInt(1); //根据列下标获得值
System.out.println(empNo);
String ename = rs.getString("ename"); //根据列名获得值，推荐这种方式
System.out.println(ename);
Date joinDate = rs.getDate("hireDate");
System.out.println(joinDate);
Double sal = rs.getDouble("sal");
System.out.println(sal);
System.out.println("============");
}
//6、关闭资源
rs.close();
stmt.close();
conn.close();
}
catch (ClassNotFoundException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
catch (SQLException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
} }
}
实际上常用的是：
public class DBTool
{
private static DBTool instance; private DBTool()
{ } public static DBTool getInstance()
{
if (instance == null)
{
instance = new DBTool(); // 如果该实例为空，表示没实例化，在自己这里实例化，否则直接返回已经实例化好的对象
}
return instance;
} public Connection getConnection()
{
Connection conn = null;
try
{
Properties p = new Properties();
p.load(new FileReader("db.properties"));
String driverName = p.getProperty("driverName");
String url = p.getProperty("url");
String userName = p.getProperty("username");
String pwd = p.getProperty("password");
Class.forName(driverName);
conn = DriverManager.getConnection(url, userName, pwd);
}
catch (IOException | SQLException | ClassNotFoundException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
return conn;
} public static void closeAll(Connection conn, Statement stmt, ResultSet rs)
{
close(rs);
close(stmt);
close(conn);
} private static void close(AutoCloseable ac)
{
try
{
if (ac != null)
{
ac.close();
ac = null;
}
}
catch (Exception e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
此时驱动配置文件使用映射：
driverName = com.mysql.jdbc.Driver
url = jdbc:mysql://192.168.6.66:3307/hn
username = zxj
password = wxniit