格式:jQuery.getJSON( url [,data] [,success(data,textStatus,jqXHR)] ), 三个参数分别死请求地址, 要传递的参数, 回调函数
This is a shorthand Ajax function,which is equivalent to:
$.ajax({
url: url,
dataType: 'json',
data: data,
success: callback
});
Thesuccess
callback is passed the returned data,whichis typically a JavaScript object or array as defined by the JSON structure and parsed using the$.parseJSON()
method. It is also passed the text status of the response.
As of jQuery 1.5,thesuccess
callback function receives a"jqXHR" object(injQuery1.4,it received theXMLHttpRequest
object). However,since JSONP and cross-domain GET requests do not useXHR,in those cases thejqXHR
andtextStatus
parameters passed to the success callback are undefined.
如果在服务器端没有指定返回数据的格式, 我们可以讲返回值使用$.parseJSON()处理一下, 如果在服务器端已经处理, 那么在函数中可以直接使用。比如:
在服务器端的代码:
<%
response.setContentType("text/json");
out.println("[{\"name\":\"湖南省\",\"regionId\":134},{\"name\":\"北京市\",\"regionId\":143}]");
%>
注意:格式良好的JSON应该使用双引号讲字符串括起来。否则可能在解析的出错!
这时, 回调函数中可以直接使用:
$.getJSON("http://localhost:8080/jqueryTest2",
function(json){
alert(json[0].name);
alert(json[1].name);
});
如果在服务端没有这句:
response.setContentType("text/json");
那么在回调函数中要对返回的数据进行处理:
$.getJSON("http://localhost:8080/jqueryTest2",
function(json){
json=$.parseJSON(json);
alert(json[0].name);
alert(json[1].name);
});
$.parseJSON()方法可以将一个JSON格式的字符串解析为对象。
继续,
在jquery1.5中, 回调函数会接收XMLHttpRequest对象,
jsonp和跨域的get请求没有使用XMLHttpRequest对象(为什么?),所以jQuery.getJSON( url [,jqXHR)] )中的参数jqXHR
和textStatus在回调函数中是undefined类型的。
Additional Notes:@H_403_278@
- Due to browser security restrictions,most "Ajax" requests are subject to thesame origin policy; the request can not successfully retrieve data from a different domain,subdomain,or protocol.
- Script and JSONP requests are not subject to the same origin policy restrictions.
这是说, 大部分ajax请求由于同源策略而受到限制, 导致请求不能够成功从其他域获取数据, 所谓非同域指的是:不同的域名之间, 子域名和上级域名之间,以及不同协议的域名之间。
JSONP
If the URL includes the string "callback=?" (or similar,as defined by the server-side API),the request is treated as JSONP instead. See the discussion of thejsonp
data type in$.ajax()
for more details.
如果在jQuery.getJSON( url [,jqXHR)] )的URL后面跟上callback=?,那么这个请求会被认为死JSONP, 也就是说, 这个方法是可以跨域的。
关于跨域, 下一篇再总结。
- Due to browser security restrictions,most "Ajax" requests are subject to thesame origin policy; the request can not successfully retrieve data from a different domain,subdomain,or protocol.
- Script and JSONP requests are not subject to the same origin policy restrictions.
JSONP
If the URL includes the string "callback=?" (or similar,as defined by the server-side API),the request is treated as JSONP instead. See the discussion of thejsonp
data type in$.ajax()
for more details.