ajax入门教程 讲解一个验证用户名的实例

package dd; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.RequestDispatcher; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; public class Servlet extends HttpServlet { @Override protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub doPost(request,response); } @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub String name=request.getParameter("name"); String pwd=request.getParameter("pwd"); if(name.equals("jack_booth")){ request.setAttribute("USER","<script>alert('此网名已有人注册，请另取!')</script>"); } else request.setAttribute("USER","<script>alert('此网名可以注册!!')</script>"); RequestDispatcher dis=getServletContext().getRequestDispatcher("/index.jsp"); dis.forward(request,response); } }