一个简单的ajax验证登录

package servlet; 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; public class CheckServlet extends HttpServlet { /** * Constructor of the object. */ public CheckServlet() { super(); } /** * Destruction of the servlet. <br> */ public void destroy() { super.destroy(); // Just puts "destroy" string in log // Put your code here } /** * The doGet method of the servlet. <br> * * This method is called when a form has its tag value method equals to get. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { PrintWriter out = response.getWriter(); response.setCharacterEncoding("UTF-8"); response.setContentType("text/xml;charset=UTF-8"); response.setHeader("Cache-Control", "no-cache"); String username = (String)request.getParameter("username"); System.out.println("username:"+username); LoginClass lc = new LoginClass(); if(username.equals("") || username == null){ out.println("<response><message>Null</message></response>"); }else if(lc.checkusername(username) == 0){ out.println("<response><message>Wrong</message></response>"); }else{ out.println("<response><message>OK</message></response>"); System.out.println("存在此用户"); } out.close(); //response.getWriter().write(xml); } /** * The doPost method of the servlet. <br> * * This method is called when a form has its tag value method equals to post. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html"); PrintWriter out = response.getWriter(); doGet(request,response); out.close(); } /** * Initialization of the servlet. <br> * * @throws ServletException if an error occure */ public void init() throws ServletException { // Put your code here } }