前端插入date类型的数据到数据库

//插入 
@Override
    public boolean insertEmp(Emp emp) {
        String sql = "insert into emp(lwlEmpno,lwlEname,lwlSalary,lwlHiredate,lwlSsex) " +
                " values('" + emp.getLwlEmpno() + "','" + emp.getLwlEname() + "','" +
                emp.getLwlSalary() + "',to_date('" + emp.getLwlHiredate() + "','yyyy-mm-dd'),'" + emp.getLwlSsex() + "')";
        log.debug(sql);
        return LwlDao.exeUpdate(sql);
    }


//修改
@Override
    public boolean updateEmp(Emp emp, String oldEmpNo) {
        String sql = "update emp set lwlEmpno='" + emp.getLwlEmpno() + "',lwlEname='" + emp.getLwlEname() +
                "',lwlSalary='" + emp.getLwlSalary() +
                "',lwlHiredate=to_date('" + emp.getLwlHiredate() + "','yyyy-mm-dd'),lwlSsex='" + emp.getLwlSsex() + "'  where lwlEmpno='" + oldEmpNo + "'";
        log.debug(sql);
        return LwlDao.exeUpdate(sql);
    }


//获取
 public static List<Emp> getEmp(String sql) {
        ArrayList<Emp> lst = new ArrayList<Emp>();
        Connection conn = getConn();
        try {
            Statement st = conn.createStatement();
            ResultSet rs = st.executeQuery(sql);
            while (rs.next()) {
                Emp emp = new Emp();
                emp.setLwlEmpno((rs.getString("lwlEmpno")));
                emp.setLwlEname(rs.getString("lwlEname"));
                emp.setLwlSalary(Double.parseDouble(rs.getString("lwlSalary")));

                emp.setLwlHiredate(rs.getDate("lwlHiredate")+"");

                emp.setLwlSsex(rs.getString("lwlSsex"));
                lst.add(emp);
            }
        } catch (Exception e) {
            System.err.println(e.getMessage());
        } finally {
            if (conn != null) {
                try {
                    conn.close();
                } catch (SQLException e) {
                    System.err.println(e.getMessage());
                }
            }
        }
        return lst;
    }

public class Emp {
    private String lwlEmpno;
    private String lwlEname;
    private double lwlSalary;
    private String lwlHiredate;
    private String lwlSsex;
      
    ………………………………
}

create table emp(
  lwlEmpno varchar2(20)  primary key,
  lwlEname varchar2(20),
  lwlSalary number,
  lwlHiredate date,
  lwlSsex varchar2(3)
)