package?ajax;

import?java.io.IOException;
import?java.io.PrintWriter;

import?javax.servlet.ServletException;
import?javax.servlet.http.HttpServlet;
import?javax.servlet.http.HttpServletRequest;
import?javax.servlet.http.HttpServletResponse;
import?javax.servlet.http.HttpSession;

import?dao.UserDAO;
import?entity.User;

public?class?UserNameCheck?extends?HttpServlet?{

	private?UserDAO?dao?=?null;

	public?void?service（HttpServletRequest?request?HttpServletResponse?response）
			throws?ServletException?IOException?{

		request.setCharacterEncoding（“utf-8“）;
		response.setContentType（“text/html;charset=utf-8“）;
		PrintWriter?pw?=?response.getWriter（）;
		String?msg?=?null;
		//?從頁面獲得用戶名
		String?userName?=?request.getParameter（“username“）;
		this.dao?=?new?UserDAO（）;
		User?user?=?dao.findByUsername（userName）;

		if?（userName?==?null?||?userName?==?““）?{
			msg?=?“用戶名不能為空！“;
		}?else?if?（user?!=?null）?{
			msg?=?“用戶名已存在！“;

		}?else?{
			msg?=?“用戶名可以使用！“;
		}

		pw.println（msg）;
		pw.flush（）;
		pw.close（）;

	}

}