全面了解JAVA_BaseDAO数据处理类

package dao;import java.sql.Connection;import java.sql.DriverManager;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;public class BaseDao {  private String drive="com.microsoft.sqlserver.jdbc.SQLServerDriver";  private String url="jdbc:sqlserver://localhost:1433;DatabaseName=BookManage";  private String user="sa";  private String password="";  protected Connection conn;  protected PreparedStatement ps;  protected ResultSet rs;  public Connection getCon(){    try {      Class.forName(drive);      conn=DriverManager.getConnection(url, user, password);    } catch (ClassNotFoundException e) {      e.printStackTrace();    } catch (SQLException e) {      e.printStackTrace();    }        return conn;  }  public void allClos(ResultSet rs,PreparedStatement ps,Connection conn){        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...str){  int num=0;  try {    ps=getCon().prepareStatement(sql);    if(ps!=null){      for(int i=0;i<str.length;i++){        ps.setObject(i+1, str[i]);      }    }    num=ps.executeUpdate();  } catch (SQLException e) {    // TODO Auto-generated catch block    e.printStackTrace();  }finally   {    allClos(rs, ps, conn);  }  return num;}}