在服務器端判斷request來自Ajax請求(異步)還是傳統請求(同步)：
兩種請求在請求的Header不同，Ajax 異步請求比傳統的同步請求多了一個頭參數
1、傳統同步請求參數
accept text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
accept-charset gb2312,utf-8;q=0.7,*;q=0.7
accept-encoding gzip,deflate
accept-language zh-cn,zh;q=0.5
cache-control max-age=0
connection keep-alive
cookie JSESSIONID=1A3BED3F593EA9747C9FDA16D309AF6B
host 192.168.101.72:8080
keep-alive 300
referer http://192.168.101.72:8080/htfsweb/spring_security_login
user-agent Mozilla/5.0 (Windows; U; Windows NT 5.1; zh-CN; rv:1.9.0.15) Gecko/2009101601 Firefox/3.0.15 (.NET CLR 3.5.30729)
2、Ajax 異步請求方式
accept */*
accept-language zh-cn
referer http://192.168.101.72:8080/scm/?token=3b194bff23bf6acecea5661ac8e14c51
x-requested-with XMLHttpRequest
content-type application/x-www-form-urlencoded,text/javascript
accept-encoding gzip, deflate
user-agent Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; Trident/4.0; QQDownload 598; .NET CLR 2.0.50727; .NET CLR 3.0.04506.648; .NET CLR 3.5.21022; CIBA; .NET CLR 1.1.4322; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729; InfoPath.1)
host 192.168.101.72:8080
content-length 233
connection Keep-Alive
cache-control no-cache
cookie CSS=undefined; JSESSIONID=1B9AC25036290F7FB6823CCE1A24E541
可以看到 Ajax 請求多了個 x-requested-with ，可以利用它，request.getHeader("x-requested-with"); 為 null，則為傳統同步請求，為 XMLHttpRequest，則為 Ajax 異步請求。