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因为浏览器的同源策略，普通ajax访问跨域请求返回的json数据是不会被浏览器接受的。看下面例子可以看出是访问不到的
首先 定义webapi 后台代码
public class JsopController : ApiController { public IHttpActionResult GetAlluser() { User[] contacts = new User[] { new User{ Name="123", PhoneNo="111", EmailAddress="111@gmail.com"}, new User{ Name="456", PhoneNo="222", EmailAddress="222@gmail.com"}, new User{ Name="789", PhoneNo="333",EmailAddress="333@gmail.com"}, }; return Json<IEnumerable<User>>(contacts); } }
前台调用代码
<script src="~/Scripts/jquery-1.8.2.min.js"></script>
<ul id="contacts"></ul>
<script type="text/javascript">
$(function () {
var url = "http://localhost:16161/api/Jsop/GetAlluser";
$.getJSON(url, null, function (contacts) {
$.each(contacts, function (index, contact) {
var html = "<li><ul>";
html += "<li>Name: " + contact.Name + "</li>";
html += "<li>Phone No:" + contact.PhoneNo + "</li>";
html += "<li>Email Address: " + contact.EmailAddress + "</li>";
html += "</ul>";
$("#contacts").append($(html));
});
});
});
</script>
然后运行程序查看是不能够获得数据的。
通过查看火狐浏览firdebug 查看请求头信息，请求是请求到了，只是没有返回数据而已
Accept application/json, text/javascript, */*; q=0.01 Accept-Encoding gzip, deflate Accept-Language zh-CN,zh;q=0.8,en-US;q=0.5,en;q=0.3 Connection keep-alive Host localhost:16161 Referer http://localhost:18982/TestCors User-Agent Mozilla/5.0 (Windows NT 6.1; rv:36.0) Gecko/20100101 Firefox/36.0
下面我就介绍jsonp来跨域获取数据。
首先还是后台代码
public HttpResponseMessage GetJsonp(string callback)
{
User[] contacts = new User[]
{
new User{ Name="123", PhoneNo="111", EmailAddress="111@gmail.com"},
new User{ Name="456", PhoneNo="222", EmailAddress="222@gmail.com"},
new User{ Name="789", PhoneNo="333",EmailAddress="333@gmail.com"},
};
JavaScriptSerializer serializer = new JavaScriptSerializer();
string content = string.Format("{0}({1})", callback, serializer.Serialize(contacts));
return new HttpResponseMessage(HttpStatusCode.OK)
{
Content = new StringContent(content, Encoding.UTF8, "text/javascript")
};
}
前台调用代码
<script src="~/Scripts/jquery-1.8.2.min.js"></script>
<script type="text/javascript">
function GetList(contacts) {
$.each(contacts, function (index, contact) {
var html = "<li><ul>";
html += "<li>Name: " + contact.Name + "</li>";
html += "<li>Phone No:" + contact.PhoneNo + "</li>";
html += "<li>Email Address: " + contact.EmailAddress + "</li>";
html += "</ul>";
$("#contacts").append($(html));
});
}
</script>
<ul id="contacts"></ul>
<script type="text/javascript" src="http://localhost:16161/api/Jsop/GetJsonp?callback=GetList"></script>
通过运行查看数据返回成功了
查看火狐浏览器查看响应信息如下：
GetList([{"Name":"123","PhoneNo":"111","EmailAddress":"111@gmail.com"},{"Name":"456","PhoneNo":"222","EmailAddress":"222@gmail.com"},{"Name":"789","PhoneNo":"333","EmailAddress":"333@gmail.com"}])
他返回的不再是纯的json数据了，而是jsonp数据了。通过javascript脚本执行回调方法。不过通过jsonp这种方式是可以跨域共享，但是这只是一种<script>这个标签不受同源策略影响而已，而且这种方式只能通过http-get方式来实现而已。
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原文地址：http://www.cnblogs.com/dzpblogs/p/4376173.html
