package com.jdbc.dao;
import java.sql.*;public class BaseDAO {//打开数据库链接public Connection getConn(){Connection conn = null;try {//加载驱动Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");//打开链接conn = DriverManager.getConnection("jdbc:sqlserver://localhost:1433;DatabaseName = epetDB","sa","sa");} catch (ClassNotFoundException e) {// TODO Auto-generated catch block
                        e.printStackTrace();} catch (SQLException e) {// TODO Auto-generated catch block
                        e.printStackTrace();}return conn;}//（重写）关闭链接public void Close(Connection conn,PreparedStatement pstmt,ResultSet rs){try {//关闭结果集if (rs != null) {rs.close();}//关闭PerparedStatement对象if (pstmt != null) {pstmt.close();}//关闭链接if (conn != null) {conn.close();}} catch (Exception e) {// TODO: handle exception
                }}//（重写）关闭链接public void Close(Connection conn,PreparedStatement pstmt){try {//关闭PerparedStatement对象if (pstmt != null) {pstmt.close();}//关闭链接if (conn != null) {conn.close();}} catch (Exception e) {// TODO: handle exception
                }}//增删改操作public int Update(String sql,Object[] parm){int iRet = 0;Connection conn = null;PreparedStatement pstmt = null;try {conn = getConn();pstmt = conn.prepareStatement(sql);//循环赋值参数for (int i = 0; i < parm.length; i++) {//为预编译sql设置参数pstmt.setObject(i+1, parm);}//执行SQL语句iRet = pstmt.executeUpdate();} catch (Exception e) {e.printStackTrace();}finally{Close(conn,pstmt);}return iRet;}
}

try{
//可能出现异常的代码
}catch(Execption e){
//如果发生异常处理的代码
}finally{
//无论是否异常都会执行的代码
try catch finally java中异常处理机制

package dao;import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;public class BaseDao {private String className = "com.microsoft.sqlserver.jdbc.SQLServerDriver";private String url = "jdbc:sqlserver://localhost:1433;databasename=SQLTMP";private String user = "sa";private String pwd = "sa";private static Connection conn = null;private BaseDao(){try {Class.forName(className);conn = DriverManager.getConnection(url,user,pwd);} catch (ClassNotFoundException e) {e.printStackTrace();} catch (SQLException e) {e.printStackTrace();}}public static Connection getConn(){if(conn != null){return conn;}else{new BaseDao();return conn;}}
}