AJAX 非同步傳輸資料的問題

要非同步傳輸的資料：
Xml代碼
....
<action xsi:type="basic:JavaScript" script="index += 1;"/>
....
Ajax非同步傳輸代碼：
Js代碼 複製代碼 代碼如下:var postData = "input="+ escape(inputJSON) +"&script="+escape(xml)+
"&feedGeneral=" + escape(feedGeneral);
XmlHttpRequest.open("POST",url,true);
XmlHttpRequest.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
XmlHttpRequest.send(postData);

postData在encode和unencode，最終導致在後台Servlet中得到得到資料+被空格代替，使得script中的index += 1;變成了index = 1;從而導致後台Java代碼在跑script出現死迴圈。
在網上搜尋，發現content-type使用application/x-www-form-urlencoded後：
[來自http://www.w3.org/TR/html401/interact/forms.html#h-17.13.4.1]寫道 複製代碼 代碼如下:Control names and values are escaped. Space characters are replaced by `+', and then reserved characters are escaped as
described in [RFC1738], section 2.2: Non-alphanumeric characters are replaced by `%HH', a percent sign and two hexadecimal
digits representing the ASCII code of the character. Line breaks are represented as "CR LF" pairs (i.e., `%0D%0A').

然而使用form來提交方式來發起request卻不會出現類似的問題，而form預設的Content-Type也是application/x-www-form-urlencoded:
Js代碼 複製代碼 代碼如下:$('test').innerHTML = "<form target='_blank' id='test_form' action='./gen_feed' method='post'>"
+ "<input type='text' name='input' /><input type='text' name='script' />"
+ "<input type='text' name='feedGeneral' /><input type='hidden' name='format' value='" + this.feed_type + "'
/>"
+ "<input type='submit' value='gen' /></form>";
var test_form = $('test_form');
test_form.elements[0].value = inputJSON;
test_form.elements[1].value = script;
test_form.elements[2].value = feedGeneral;
test_form.submit();

仍未發現問題到底出在何處，暫做備忘。暫時把script中的‘+'都用‘-'代替，index += 1;改成index -= -1;呵呵，以後有人看到這段自動產生的詭異指令碼，不知道會作何感想，但現在也只能如此。