當通過JQuery向Google App Engine發送POST請求時沒有結果

Question

我試圖通過JQuery AJAX向我的GAE應用發送POST請求，但是我沒有收到響應數據。我有一個非常簡單的servlet，它簡單地回顯我傳入的「msg」。還覆蓋了doOptions。

@Override 
protected void doOptions(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException 
{ 
    resp.setHeader("Access-Control-Allow-Origin", "*"); 
    resp.setHeader("Access-Control-Allow-Methods", "GET, POST, OPTIONS"); 
    resp.setHeader("Access-Control-Max-Age", "1728000"); 
} 

@Override 
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException 
{ 
    resp.setContentType("text/javascript"); 
    resp.setCharacterEncoding("utf-8"); 

    String msg = req.getParameter("msg"); 
    resp.getWriter().print(msg); 
} 

這是我如何通過JQuery的AJAX

var parameters = {msg:"hello"}; 
$.ajax({ 
    type: 'POST', 
    url: service_url, 
    data: parameters, 
    success: successhandler, 
    error: errorhandler 
}) 

稱爲如果我看我的交互是通過螢火，我看到這一點。

首先，JQuery的發出一個OPTIONS請求

Host lessondesigner.appspot.com 
User-Agent Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.2.8) Gecko/20100722 Firefox/3.6.8 
Accept text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 
Accept-Language en-us,en;q=0.5 
Accept-Encoding gzip,deflate 
Accept-Charset ISO-8859-1,utf-8;q=0.7,*;q=0.7 
Keep-Alive 115 
Connection keep-alive 
Origin lessondesigner.appspot.com 
Access-Control-Request-Me... POST 

Access-Control-Allow-Orig... * 
Access-Control-Allow-Meth... GET, POST, OPTIONS 
Access-Control-Max-Age 1728000 
Date Mon, 06 Sep 2010 01:11:56 GMT 
Content-Type text/html 
Server Google Frontend 
Content-Length 0 

下發出POST請求

Host lessondesigner.appspot.com 
User-Agent Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.2.8) Gecko/20100722 Firefox/3.6.8 
Accept application/json, text/javascript, */* 
Accept-Language en-us,en;q=0.5 
Accept-Encoding gzip,deflate 
Accept-Charset ISO-8859-1,utf-8;q=0.7,*;q=0.7 
Keep-Alive 115 
Connection keep-alive 
Content-Type application/x-www-form-urlencoded; charset=UTF-8 
Referer lessondesigner.appspot.com/testAjax.html 
Content-Length 21 
Origin lessondesigner.appspot.com 
Pragma no-cache 
Cache-Control no-cache 

Content-Type text/javascript; charset=utf-8 
Content-Encoding gzip 
Date Mon, 06 Sep 2010 01:11:56 GMT 
Server Google Frontend 
Cache-Control private, x-gzip-ok="" 
Content-Length 25 

然而，我得不到任何回報的響應！如果我使用Curl，它工作正常。

curl -d "msg=hello" lessondesigner.appspot.com/lessondesigner 

我回來

"hello" 

有誰知道這是爲什麼？另外，爲什麼JQuery首先執行OPTIONS請求？它甚至不跨域。

Answer 1

嘗試flushing筆者

Answer 2

想通了。這是一個跨源資源共享問題。這裏有一篇很棒的文章。

http://hacks.mozilla.org/2009/07/cross-site-xmlhttprequest-with-cors/

基本上如果一個HTTPRequest，報頭包含一個「原點」字段，服務器必須具有「訪問控制允許來源」響應回覆。在我的情況下，我是在OPTIONS請求中執行它，但不是在POST請求中執行它。因此，firefox沒有返回我的內容數據。爲了解決這個問題，我必須這樣做。

@Override 
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException 
{ 
    resp.setHeader("Access-Control-Allow-Origin", "*"); 
    resp.setContentType("text/javascript"); 
    resp.setCharacterEncoding("utf-8"); 
    String msg = req.getParameter("msg"); 
    resp.getWriter().print(msg); 
}