LoginServlet源码解析

public class LoginServlet extends HttpServlet{    private static final long serialVersionUID = 1L;    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException    {        try{            /* 0.取出表单中的用户提交数据 */            String username=request.getParameter("username");            System.out.println(username);            String pwd=request.getParameter("pwd");            String usercode=request.getParameter("usercode");//用户输入的验证码            //1.验证验证码            String realcode=(String) request.getSession(true).getAttribute("realcode");//session中的验证码            if(!realcode.equalsIgnoreCase(usercode))//如果两个验证码不一致            {                request.setAttribute("msg", "验证码输入错误");                request.getRequestDispatcher("/index.jsp").forward(request, response);            }            else            {                User user = new UserDAO().getByName(username);                if(null == user)                {                    request.setAttribute("msg", "用户名不存在");                    request.getRequestDispatcher("/index.jsp").forward(request, response);                }                else if(!user.getPwd().equals(pwd))                {                    request.setAttribute("msg", "密码输入错误");                    request.getRequestDispatcher("/index.jsp").forward(request, response);                }                else                {                    request.getSession(true).setAttribute("user", user);                    request.setAttribute("msg", "登录成功");                    request.getRequestDispatcher("/vetsearch.jsp").forward(request, response);                }            }        }        catch(Exception e)        {            request.setAttribute("msg", e.getMessage());            request.getRequestDispatcher("/index.jsp").forward(request, response);        }    }

上述源码是登录页面的Servlet处理