ajax判断存在验证
servlet:
boolean validate = userService.validateUserName(username);out.print(validate);
function validate(){var username = $("#username").val();$.ajax({url:"/XXX/userManager",cache:false,type:"POST",data:"type=vali&username="+username,success:function(data){if(data=="true"){var div = document.getElementById("valiDiv");div.style.display = "block";}else{alert("此用户已存在！");$("#username").val("");}}});}function clearDiv(){var div = document.getElementById("valiDiv");div.style.display = "none";}<div id="valiDiv" style=" position:absolute;top:65px;left:550px; width:150px; height:15px; font-size:13; color:#33FF00; font-weight:bold; text-align:center; display:none;"><img src="<%=path %>/images/right.gif" width="15px" height="15px" /> 此用户名可以使用</div><form name="aform" method="post" ><table width="100%" border="0" cellpadding="0" cellspacing="1" id="ConTable"> <tr> <td align="right">用户名：</td> <td><input type="text" name="username" id="username" onBlur="validate()" onFocus="clearDiv()" /><FONT color="red">*</FONT></td> </tr></table></form>