ajax中的setRequestHeader设置请求头

时间：2016-01-25 16:56:00 收藏：0 阅读：11292

1、问题引发点:

前不久发现一个问题: 前端并没有设置请求头信息里面的Accept-Encoding:gzip...但是在请求头中可以明显的看到Accept-Encoding:gzip, deflate, sdch,并且我尝试修改这个请求头，发现不生效；

2、XMLHttpRequest对象提供了一个设置请求头的方法:setRequestHeader，对应的jQuery可以再beforeSend回调里面设置请求头：

$.ajax({
    type: "GET",
    url: "test.php",
    success: function(data) {
        console.log(data);
    },
    beforeSend: function(xhr) {
        xhr.setRequestHeader("User-Agent", "headertest");
    }
});

3、后来看W3C标准文档发现，这个请求头不是什么都可以设置的，标准里面明确规定了以下请求头信息是浏览器控制，开发者不允许设置这些请求头

Terminate these steps if header is a case-insensitive match for one of the following headers:

Accept-Charset
Accept-Encoding
Access-Control-Request-Headers
Access-Control-Request-Method
Connection
Content-Length
Cookie
Cookie2
Date
DNT
Expect
Host
Keep-Alive
Origin
Referer
TE
Trailer
Transfer-Encoding
Upgrade
User-Agent
Via

… or if the start of header is a case-insensitive match for Proxy- or Sec- (including when header is just Proxy- or Sec-).

The above headers are controlled by the user agent to let it control those aspects of transport. This guarantees data integrity to some extent. Header names starting with Sec- are not allowed to be set to allow new headers to be minted that are guaranteed not to come fromXMLHttpRequest.

4、例子:

testAE.html

<!DOCTYPE html>
<html>
<head>
	<title>test</title>
</head>
<script type="text/javascript" src="./jquery.1.8.1.min.js"></script>
<body>
<script type="text/javascript">
$.ajax({
    type: "GET",
    url: "./testAE.php",
    success: function(data) {
        $("body").append(data);
    },
    beforeSend: function(xhr) {
        xhr.setRequestHeader("Accept-Encoding", "testAE");
    }
});
</script>
</body>
</html>

testAE.php

<?php
/*回传ACCEPT_ENCODING*/
echo $_SERVER[‘HTTP_ACCEPT_ENCODING‘];
?>

chrome:

技术分享

ie:

技术分享

控制台:

技术分享

可以看到jQuery也会提示你这样设置是不安全的。

在mozila官方论坛里面也有相应的讨论：Ajax setRequestHeader;