ajax三种发送方式demo

.ajax方法:
```
$.ajax({
url:"${pageContext.request.contextPath}/user/checkUserName",
data:{"username":username},
type:"post",
dataType:"json",
success:function (data) {
alert(data);
}
});

.post方法

$.post(
"${pageContext.request.contextPath}/user/isUniqueUsername", //url
{"username":username}, //data
function(data){}, //success
'text' //dataType
);