jsp頁面
<head><script type="text/javascript" src="js/register.js"></script></head><table><td>用戶名：</td> <td> <input type="text" name="r_name" id="r_name" onblur="CheckUserName()"> <span id="span01"></span> </td></table>
js文件夾下的register.js
//創建對象function ajaxFunction(){ var xmlHttp; try{ // 適用于IE7+, Firefox, Chrome, Opera, Safari xmlHttp=new XMLHttpRequest(); } catch(e){ try{ //Internet Explorer xmlHttp=new ActiveXObject("Msxml2.XMLHTTP"); } catch(e){ try{ // 適用于IE6, IE5 xmlHttp=new ActiveXObject("Microsoft.XMLHTTP"); } catch(e){ xmlHttp=false; } } } return xmlHttp; }var flag=ture; function CheckUserName(){ //獲取jsp頁面輸入的值var name=document.getElementById("r_name").value; if(name==""||name==null){ document.getElementById("span01").innerHTML="<font color='red'>用戶名不能為空！</font>" flag=false; }else{ //1.創建對象var request=ajaxFunction(); //2.發送請求request.open("POST","/StudyWeb/CheckUserNameServlet",true);//true表示異步提交//注冊狀態改變監聽，獲取服務器傳送過來的數據request.onreadystatechange=function(){ //readyState==4表示請求已經完成，且響應已就緒。status==200表示“OK”if(request.readyState==4 && request.status==200){var data=request.responseText;//獲取CheckUserNameServlet中response中存儲的值if(data == 1){ document.getElementById("span01").innerHTML="<font color='red'>用戶名已存在！</font>" flag=false; }else{ document.getElementById("span01").innerHTML="<font color='green'>√</font>" flag=true; } } } //如果是post方式帶數據，那么這里要添加頭，說明提交的數據類型是一個經過url編碼的form表單數據request.setRequestHeader("Content-type","application/x-www-form-urlencoded;charset=UTF-8"); //帶數據過去，在send方法里填寫表單數據request.send("name="+name); } return flag; }后臺StudyWeb項目下的CheckUserNameServlet
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//獲取ajax發送過來的name值String r_name=request.getParameter("name"); try { //檢驗是否存在該用戶名boolean isExist=userService.CheckUserName(r_name); System.out.println("isExist"+isExist); //通知頁面，到底有沒有if(isExist){ response.getWriter().println(1);//存在用戶名}else{ response.getWriter().println(2);//不存在該用戶} } catch (Exception e) { e.printStackTrace(); } }UserDaoImpl中方法的實現
public boolean CheckUserName(String u_name) { boolean flag=false; String sql="select u_id,u_name,u_password,u_email,u_phone from user where u_name=?"; conn=super.getConnection(); try { pstmt=conn.prepareStatement(sql); pstmt.setString(1,u_name); rs=pstmt.executeQuery();//如果存在我輸入的用戶名和數據庫表中已有的用戶名相同時if(rs.next()){flag=true; } } catch (SQLException e) { e.printStackTrace(); }finally{ super.closeAll(conn, pstmt, stmt, rs); } return flag; }
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