我正在竭尽全力试图弄清楚如何使用jQuery对ASMX Web服务进行JSONP调用。这些只是我已经阅读并且没有找到任何解决方案的一些页面:
How to call external webservice using jquery "jsonp"?
Posting cross-domain JSON to ASP.NET with jQuery
Error while accessing ASP.net webservice using JQuery - JSONP
Set Headers with jQuery.ajax and JSONP?
http://www.codeproject.com/Articles/43038/Accessing-Remote-ASP-NET-Web-Services-Using-JSONP
http://encosia.com/using-jquery-to-consume-aspnet-json-web-services/
等等...
这是我的示例.NET Web方法:
[WebMethod]
[ScriptMethod(UseHttpGet = true, ResponseFormat = ResponseFormat.Json)]
public void GetEmployee(string employeeId, string callback)
{
// Get the employee object from the Factory.
Employee requestedEmployee = EmployeeFactory.GetEmployee(employeeId);
if(requestedEmployee != null)
{
// Return the padded JSON to the caller.
CrossDomainUtility.SendJsonP(callback, requestedEmployee.ToJson());
}
}
这是SendJsonP():
public static void SendJsonP(string callback, string json)
{
// Clear any response that has already been prepared.
HttpContext.Current.Response.Clear();
// Set the content type to javascript, since we are technically returning Javascript code.
HttpContext.Current.Response.ContentType = "application/javascript";
// Create a function call by wrapping the JSON with the callback function name.
HttpContext.Current.Response.Write(String.Format("{0}({1})", callback, json));
// Complete this request, to prevent the ASMX web service from doing anything else.
HttpContext.Current.ApplicationInstance.CompleteRequest();
}
这是一些示例jquery代码:
$.ajax({
url: 'http://devserver/service/service.asmx/GetEmployee',
dataType: 'jsonp',
contentType: 'application/json',
data: { employeeId: '123456789' }
});
我的Web服务装饰有[ScriptService]，并且将我的web.config配置为使用ScriptHandlerFactory处理* .asmx。
我尝试使用Content-Type为'application/json'时ASMX使用的内置JSON序列化，但是有两个问题:由于需要用空格填充，因此它不适用于JSONP。 .NET不支持的JSON。它也不起作用，因为为了序列化JSON，ASMX需要一个'ContentType:application/json' header ，但是jQuery在发送GET请求时会忽略ContentType header (大概是因为它没有发送任何内容)。我试过在Global.asax Application_BeginRequest()中设置Request.ContentType =“application/json”，但这没有任何作用。我也尝试过使用beforeSend()在jQuery中设置请求 header ，但没有运气。
因此，由于无法使用内置的.NET管道轻松使它正常工作，因此我滚动了自己的技术，该技术对Response主体执行原始写入(因此，使用SendJsonP()方法)。但是我仍然遇到问题，因为即使GetEmployee()Web方法未返回值，.NET也会引发序列化错误，因为它试图将对象序列化为XML，因为我无法传递ContentType的“application”/json'和GET请求。
因此，由于无论如何我都无法让jQuery添加ContentType，因此我想通过仅使用Fiddler2创建手动请求来测试我的Web服务:
GET http://devserver/service/service.asmx/GetEmployee?callback=createMember&memberId=123456789
User-Agent: Fiddler
Content-Type: application/json
Host: devserver
...并且由于我的参数不是JSON，因此出现以下错误:
{"Message":"Invalid JSON primitive: createMember [....] }
所以毕竟，我还有几个问题:
GetEmployee？{callback:“createMember”，memberId:“99999999”}
GetEmployee？callback = {callback:“createMember”}＆memberId = {memberId:“123456789”}
最佳答案
我刚刚决定手动处理JSONP请求。在我的解决方案中，用户必须通过GET请求提供两个查询字符串参数，以表明他们想要JSONP结果:callback = callbackFunctionName和jsonp = true。如果两者都收到，我将进行手动处理，否则请求将继续发送到标准ASMX处理器上。
我创建了一个新的JsonPUtility帮助器类，该类已作为调用添加到HttpApplication.BeginRequest事件中:
public class Global : System.Web.HttpApplication
{
protected void Application_BeginRequest(object sender, EventArgs e)
{
// Requests for JSONP requests must be handled manually due to the limitations of JSONP ASMX.
JsonPUtility.ProcessJsonPRequest();
}
}
这是JsonPUtility类:
/*
* JSON is Javascript Object Notation, a standard way of serializing objects in Javascript and
* other languages. For more information see http://www.json.org/.
*
* JSONP is a technique to enable the execution of Javascript that resides in a different domain. It
* works by exploiting the exception granted to the <script> tag which allows content to be loaded
* from a different domain. By contrast, making "regular" AJAX calls to a different domain will
* not work, usually throwing an "Access Denied" or "No Transport" error.
*
* JSONP (the "P" stands for "Padding") is regular JSON wrapped in a Javascript function call (the
* "Padding"). Take for example this standard JSON object:
* { "Name" : "John", "Age" : 14, "Gender" : "Male" }
*
* JSONP will turn that JSON into a valid Javascript function call by using the JSON as an argument
* to the callback function provided by the caller. For example, if the caller provides a callback
* value of 'processResults', the resulting JSONP looks like this:
* processResults({ "Name" : "John", "Age" : 14, "Gender" : "Male" });
*
* The processResults() function will then be able to use the JSON object just like a regular object.
* Note that the callback function must be implemented on the page that receives the JSONP, otherwise
* a standard Javascript error will occur.
*
* The real "trick" to cross-domain script execution is dynamically creating a "script" tag on the
* client for every JSONP request, using the web service URL as the "src" attribute. This will cause
* the browser to automatically download and execute the script that is loaded from the URL,
* effectively bypassing the same-domain origin policy.
*/
public static class JsonPUtility
{
/*
* SendJsonP(string callback, string json)
*
* This method takes the provided 'json' string, wraps it so that it is a parameter to the 'callback'
* function, clears any existing response text, writes the resulting Javascript code to the
* response, and ends the response.
*
* For example, given these two parameters...
* callback = "callbackFunction"
* json = "{ 'FOO': 'BAR', 'JOO': 'MAR' }"
*
* ... the following code is returned to the client in an HTTP response with a content-type of
* 'application/javascript':
* callbackFunction({ 'FOO': 'BAR', 'JOO': 'MAR' });
*
*/
public static void SendJsonP(string callback, string json)
{
// Clear any response that has already been prepared.
HttpContext.Current.Response.Clear();
// Set the content type to javascript, since we are technically returning Javascript code.
HttpContext.Current.Response.ContentType = "application/javascript";
// Create a function call by wrapping the JSON with the callback function name.
HttpContext.Current.Response.Write(String.Format("{0}({1});", callback, json));
// Complete this request, to prevent the ASMX web service from doing anything else.
HttpContext.Current.ApplicationInstance.CompleteRequest();
}
/*
* bool IsJsonPRequest()
*
* Determines whether or not the current request is for JSONP javascript code.
*
* This is the criteria for making a JSONP request to this web service:
* 1. Include the jsonp parameter. Its value is not important - we recommend using jsonp=true
* to increase clarity.
* 2. Include the callback=string parameter so we know what function call to wrap around
* the requested JSON.
*/
public static bool IsJsonPRequest()
{
// Store the context to the current request.
var request = HttpContext.Current.Request;
// If a 'jsonp' or a 'callback' parameter was not provided, this isn't a JSONP request.
if (request.QueryString["jsonp"] == null || String.IsNullOrEmpty(request.QueryString["callback"]))
return false;
// Since both parameters were provided, this is a jsonp request.
return true;
}
/*
* ProcessJsonPRequest()
*
* Manual processing is required for JSONP requests due to limitations in ASMX web services.
*/
public static void ProcessJsonPRequest()
{
// If this isn't a JSONP request, simply return and continue regular request processing.
if (!IsJsonPRequest())
return;
// Store the context to the HTTP request.
var request = HttpContext.Current.Request;
// Store the callback function that will be wrapped around the JSON string.
string callback = request.QueryString["callback"];
// Create a place to store the object that will be serialized into JSON.
object objectForJson = null;
// Store the web service method name that is being requested. It is always going to follow the
// final slash after the .asmx extension, and will continue until the question mark that marks
// the query string.
int methodNameStartIndex = request.RawUrl.ToUpper().IndexOf(".ASMX/") + 6;
int methodNameLength = (request.RawUrl.IndexOf("?")) - methodNameStartIndex;
string requestMethod = request.RawUrl.Substring(methodNameStartIndex, methodNameLength);
// Create a place to store the string ID of the object that is going to be looked-up.
string lookupId = null;
// Based on the request URL, figure out the method that will create a reference for the objectForJson variable.
switch (requestMethod)
{
case "GetEmployee":
// Get the employee's ID from the query string.
lookupId = request.QueryString["employeeId"];
// If the employee ID was provided, get a Employee object.
if (!String.IsNullOrEmpty(lookupId))
objectForJson = Factory.GetEmployee(lookupId);
break;
case "GetManager":
// Get the manager's ID from the query string.
lookupId = request.QueryString["managerId"];
// If the manager ID was provided, get a Manager object.
if (!String.IsNullOrEmpty(lookupId))
objectForJson = Factory.GetManager(lookupId);
break;
case "GetOrder":
// Get the order ID from the query string.
lookupId = request.QueryString["orderId"];
// If the order ID was provided, get the object.
if (!String.IsNullOrEmpty(lookupId))
objectForJson = Factory.GetOrder(lookupId);
break;
default:
// If the request method wasn't handled, throw an exception.
throw new ArgumentException("Unknown request method '" + requestMethod + "'.");
}
// Create a .NET framework object to serialize the object into JSON.
JavaScriptSerializer jsonSerializer = new JavaScriptSerializer();
// Serialize the object into JSON. If objectForJson is null, the callback function will be passed a parameter of null (e.g. callback(null)).
string json = jsonSerializer.Serialize(objectForJson);
// Send the JSONP string back to the caller.
SendJsonP(callback, json);
}
}
我希望这可以在将来对某人有所帮助。
谢谢，
文斯
关于jquery - JSONP和ASMX Web服务，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/13884253/