1. Front-end page
<input name="USERID" type="text" id="USERID" /> //check if username exists <script> $("#USERID").blur(function(){ var USERID = $(this).val(); $.ajax({ url: "checkUserName.jsp", type: "POST", data:{"USERID":USERID}, dataType: "text", async: false,//Synchronous execution //error: function(){alert("erro");}, success: function(data){ if(data == 1){ $("#erroInfo").next("span").hide(); $("#erroInfo").show(); $("#erroInfo").html(" Username already exists, please re-enter!"); }else{ $("#erroInfo").next("span").show(); $("#erroInfo").hide(); } } }); }); </script>2.java to write background processing
String USERID=request.getParameter("USERID"); String strSQL = "select * from d_zwuser where userid = '"+USERID+"'"; DBService dbservice = new DBService(); String result = ""; DBSet dbset = dbservice.getSelectSet(strSQL); if(dbset.size() > 0){ //result = " Username already exists, please re-enter!"; result="1"; } response.getWriter().flush(); response.setCharacterEncoding("utf-8"); response.getWriter().print(result); response.getWriter().flush();