一，为何封装万能dao

• 不用框架，纯jdbc连接数据库，会用到dao包，如果每个表都要写增删改查，一个dao至少四个方法，dao会有大量代码重复，所以封装dao包，解决sql参数的问题。
• 提高代码复用率
• 更好用，只要sql，和参数数组

二，代码实现

• 要求，有连接Oracle的jar包

package dao;import java.sql.*;/*** * @author echo lovely**/
public class ToolDao {static {try {Class.forName("oracle.jdbc.OracleDriver");} catch (ClassNotFoundException e) {e.printStackTrace();}}static Connection conn = null;static PreparedStatement ps = null;static ResultSet rs = null;public static Connection getConn() throws SQLException {String url = "jdbc:oracle:thin:127.0.0.1:1521:orcl";conn = DriverManager.getConnection(url, "scott", "scott");return conn;}public static void closeAll() {try {if (rs != null)rs.close();if (ps != null)ps.close();if (conn != null)conn.close();} catch (SQLException e) {e.printStackTrace();}}	public int executeUpdate(String sql, Object[] objs) {int i = -1;try {conn = getConn();ps = conn.prepareStatement(sql);if (objs != null) {for (int j = 0; j < objs.length; j++) {ps.setObject(j + 1, objs[j]);}// 不能为空可增删改i = ps.executeUpdate();}} catch (SQLException e) {e.printStackTrace();} finally {closeAll();}return i;}public ResultSet executeQuery(String sql, Object[] objs) {try {conn = getConn();ps = conn.prepareStatement(sql);if (objs != null) {for (int j = 0; j < objs.length; j++) {ps.setObject(j + 1, objs[j]);}}rs = ps.executeQuery();} catch (SQLException e) {e.printStackTrace();} finally {// closeAll();}return rs;}}