原因：ajax请求只是个“字符型”的请求，即请求的内容是以文本类型存放的。文件的下载是以二进制形式进行的，ajax没法解析后台返回的文件流，所以无法处理二进制流response输出来下载文件。
使用form表单提交实现文件下载
这有已经封装的jq方法。实现方式可以看代码实现。
jq插件代码
/**
* Created by wpf on 2017/12/20.
*/
/*
* jQuery File Download Plugin v1.4.5
*
* http://www.johnculviner.com
*
* Copyright (c) 2013 - John Culviner
*
* Licensed under the MIT license:
* http://www.opensource.org/licenses/mit-license.php
*
* !!!!NOTE!!!!
* You must also write a cookie in conjunction with using this plugin as mentioned in the orignal post:
* http://johnculviner.com/jquery-file-download-plugin-for-ajax-like-feature-rich-file-downloads/
* !!!!NOTE!!!!
*/
(function($, window){
// i'll just put them here to get evaluated on script load
var htmlSpecialCharsRegEx = /[<>&\r\n"']/gm;
var htmlSpecialCharsPlaceHolders = {
'<': 'lt;',
'>': 'gt;',
'&': 'amp;',
'\r': "#13;",
'\n': "#10;",
'"': 'quot;',
"'": '#39;' /*single quotes just to be safe, IE8 doesn't support ', so use ' instead */
};
$.extend({
//
//$.fileDownload('/path/to/url/', options)
// see directly below for possible 'options'
fileDownload: function (fileUrl, options) {
//provide some reasonable defaults to any unspecified options below
var settings = $.extend({
//
//Requires jQuery UI: provide a message to display to the user when the file download is being prepared before the browser's dialog appears
//
preparingMessageHtml: null,
//
//Requires jQuery UI: provide a message to display to the user when a file download fails
//
failMessageHtml: null,
//
//the stock android browser straight up doesn't support file downloads initiated by a non GET: http://code.google.com/p/android/issues/detail?id=1780
//specify a message here to display if a user tries with an android browser
//if jQuery UI is installed this will be a dialog, otherwise it will be an alert
//Set to null to disable the message and attempt to download anyway
//
androidPostUnsupportedMessageHtml: "Unfortunately your Android browser doesn't support this type of file download. Please try again with a different browser.",
//
//Requires jQuery UI: options to pass into jQuery UI Dialog
//
dialogOptions: { modal: true },
//
//a function to call while the dowload is being prepared before the browser's dialog appears
//Args:
// url - the original url attempted
//
prepareCallback: function (url) { },
//
//a function to call after a file download successfully completed
//Args:
// url - the original url attempted
//
successCallback: function (url) { },
//
//a function to call after a file download request was canceled
//Args:
// url - the original url attempted
//
abortCallback: function (url) { },
//
//a function to call after a file download failed
//Args:
// responseHtml - the html that came back in response to the file download. this won't necessarily come back depending on the browser.
// in less than IE9 a cross domain error occurs because 500+ errors cause a cross domain issue due to IE subbing out the
// server's error message with a "helpful" IE built in message
// url - the original url attempted
// error - original error cautch from exception
//
failCallback: function (responseHtml, url, error) { },
//
// the HTTP method to use. Defaults to "GET".
//
httpMethod: "GET",
//
// if specified will perform a "httpMethod" request to the specified 'fileUrl' using the specified data.
// data must be an object (which will be $.param serialized) or already a key=value param string
//
data: null,
//
//a period in milliseconds to poll to determine if a successful file download has occured or not
//
checkInterval: 100,
//
//the cookie name to indicate if a file download has occured
//
cookieName: "fileDownload",
//
//the cookie value for the above name to indicate that a file download has occured
//
cookieValue: "true",
//
//the cookie path for above name value pair
//
cookiePath: "/",
//
//if specified it will be used when attempting to clear the above name value pair
//useful for when downloads are being served on a subdomain (e.g. downloads.example.com)
//
cookieDomain: null,
//
//the title for the popup second window as a download is processing in the case of a mobile browser
//
popupWindowTitle: "Initiating file download...",
//
//Functionality to encode HTML entities for a POST, need this if data is an object with properties whose values contains strings with quotation marks.
//HTML entity encoding is done by replacing all &,<,>,',",\r,\n characters.
//Note that some browsers will POST the string htmlentity-encoded whilst others will decode it before POSTing.
//It is recommended that on the server, htmlentity decoding is done irrespective.
//
encodeHTMLEntities: true
}, options);
var deferred = new $.Deferred();
//Setup mobile browser detection: Partial credit: http://detectmobilebrowser.com/
var userAgent = (navigator.userAgent || navigator.vendor || window.opera).toLowerCase();
var isIos; //has full support of features in iOS 4.0+, uses a new window to accomplish this.
var isAndroid; //has full support of GET features in 4.0+ by using a new window. Non-GET is completely unsupported by the browser. See above for specifying a message.
var isOtherMobileBrowser; //there is no way to reliably guess here so all other mobile devices will GET and POST to the current window.
if (/ip(ad|hone|od)/.test(userAgent)) {
isIos = true;
} else if (userAgent.indexOf('android') !== -1) {
isAndroid = true;
} else {
isOtherMobileBrowser = /avantgo|bada\/|blackberry|blazer|compal|elaine|fennec|hiptop|playbook|silk|iemobile|iris|kindle|lge |maemo|midp|mmp|netfront|opera m(ob|in)i|palm( os)?|phone|p(ixi|re)\/|plucker|pocket|psp|symbian|treo|up\.(browser|link)|vodafone|wap|windows (ce|phone)|xda|xiino/i.test(userAgent) || /1207|6310|6590|3gso|4thp|50[1-6]i|770s|802s|a wa|abac|ac(er|oo|s\-)|ai(ko|rn)|al(av|ca|co)|amoi|an(ex|ny|yw)|aptu|ar(ch|go)|as(te|us)|attw|au(di|\-m|r |s )|avan|be(ck|ll|nq)|bi(lb|rd)|bl(ac|az)|br(e|v)w|bumb|bw\-(n|u)|c55\/|capi|ccwa|cdm\-|cell|chtm|cldc|cmd\-|co(mp|nd)|craw|da(it|ll|ng)|dbte|dc\-s|devi|dica|dmob|do(c|p)o|ds(12|\-d)|el(49|ai)|em(l2|ul)|er(ic|k0)|esl8|ez([4-7]0|os|wa|ze)|fetc|fly(\-|_)|g1 u|g560|gene|gf\-5|g\-mo|go(\.w|od)|gr(ad|un)|haie|hcit|hd\-(m|p|t)|hei\-|hi(pt|ta)|hp( i|ip)|hs\-c|ht(c(\-| |_|a|g|p|s|t)|tp)|hu(aw|tc)|i\-(20|go|ma)|i230|iac( |\-|\/)|ibro|idea|ig01|ikom|im1k|inno|ipaq|iris|ja(t|v)a|jbro|jemu|jigs|kddi|keji|kgt( |\/)|klon|kpt |kwc\-|kyo(c|k)|le(no|xi)|lg( g|\/(k|l|u)|50|54|e\-|e\/|\-[a-w])|libw|lynx|m1\-w|m3ga|m50\/|ma(te|ui|xo)|mc(01|21|ca)|m\-cr|me(di|rc|ri)|mi(o8|oa|ts)|mmef|mo(01|02|bi|de|do|t(\-| |o|v)|zz)|mt(50|p1|v )|mwbp|mywa|n10[0-2]|n20[2-3]|n30(0|2)|n50(0|2|5)|n7(0(0|1)|10)|ne((c|m)\-|on|tf|wf|wg|wt)|nok(6|i)|nzph|o2im|op(ti|wv)|oran|owg1|p800|pan(a|d|t)|pdxg|pg(13|\-([1-8]|c))|phil|pire|pl(ay|uc)|pn\-2|po(ck|rt|se)|prox|psio|pt\-g|qa\-a|qc(07|12|21|32|60|\-[2-7]|i\-)|qtek|r380|r600|raks|rim9|ro(ve|zo)|s55\/|sa(ge|ma|mm|ms|ny|va)|sc(01|h\-|oo|p\-)|sdk\/|se(c(\-|0|1)|47|mc|nd|ri)|sgh\-|shar|sie(\-|m)|sk\-0|sl(45|id)|sm(al|ar|b3|it|t5)|so(ft|ny)|sp(01|h\-|v\-|v )|sy(01|mb)|t2(18|50)|t6(00|10|18)|ta(gt|lk)|tcl\-|tdg\-|tel(i|m)|tim\-|t\-mo|to(pl|sh)|ts(70|m\-|m3|m5)|tx\-9|up(\.b|g1|si)|utst|v400|v750|veri|vi(rg|te)|vk(40|5[0-3]|\-v)|vm40|voda|vulc|vx(52|53|60|61|70|80|81|83|85|98)|w3c(\-| )|webc|whit|wi(g |nc|nw)|wmlb|wonu|x700|xda(\-|2|g)|yas\-|your|zeto|zte\-/i.test(userAgent.substr(0, 4));
}
var httpMethodUpper = settings.httpMethod.toUpperCase();
if (isAndroid && httpMethodUpper !== "GET" && settings.androidPostUnsupportedMessageHtml) {
//the stock android browser straight up doesn't support file downloads initiated by non GET requests: http://code.google.com/p/android/issues/detail?id=1780
if ($().dialog) {
$("<div>").html(settings.androidPostUnsupportedMessageHtml).dialog(settings.dialogOptions);
} else {
alert(settings.androidPostUnsupportedMessageHtml);
}
return deferred.reject();
}
var $preparingDialog = null;
var internalCallbacks = {
onPrepare: function (url) {
//wire up a jquery dialog to display the preparing message if specified
if (settings.preparingMessageHtml) {
$preparingDialog = $("<div>").html(settings.preparingMessageHtml).dialog(settings.dialogOptions);
} else if (settings.prepareCallback) {
settings.prepareCallback(url);
}
},
onSuccess: function (url) {
//remove the perparing message if it was specified
if ($preparingDialog) {
$preparingDialog.dialog('close');
}
settings.successCallback(url);
deferred.resolve(url);
},
onAbort: function (url) {
//remove the perparing message if it was specified
if ($preparingDialog) {
$preparingDialog.dialog('close');
};
settings.abortCallback(url);
deferred.reject(url);
},
onFail: function (responseHtml, url, error) {
//remove the perparing message if it was specified
if ($preparingDialog) {
$preparingDialog.dialog('close');
}
//wire up a jquery dialog to display the fail message if specified
if (settings.failMessageHtml) {
$("<div>").html(settings.failMessageHtml).dialog(settings.dialogOptions);
}
settings.failCallback(responseHtml, url, error);
deferred.reject(responseHtml, url);
}
};
internalCallbacks.onPrepare(fileUrl);
//make settings.data a param string if it exists and isn't already
if (settings.data !== null && typeof settings.data !== "string") {
settings.data = $.param(settings.data);
}
var $iframe,
downloadWindow,
formDoc,
$form;
if (httpMethodUpper === "GET") {
if (settings.data !== null) {
//need to merge any fileUrl params with the data object
var qsStart = fileUrl.indexOf('?');
if (qsStart !== -1) {
//we have a querystring in the url
if (fileUrl.substring(fileUrl.length - 1) !== "&") {
fileUrl = fileUrl + "&";
}
} else {
fileUrl = fileUrl + "?";
}
fileUrl = fileUrl + settings.data;
}
if (isIos || isAndroid) {
downloadWindow = window.open(fileUrl);
downloadWindow.document.title = settings.popupWindowTitle;
window.focus();
} else if (isOtherMobileBrowser) {
window.location(fileUrl);
} else {
//create a temporary iframe that is used to request the fileUrl as a GET request
$iframe = $("<iframe>")
.hide()
.prop("src", fileUrl)
.appendTo("body");
}
} else {
var formInnerHtml = "";
if (settings.data !== null) {
$.each(settings.data.replace(/\+/g, ' ').split("&"), function () {
var kvp = this.split("=");
//Issue: When value contains sign '=' then the kvp array does have more than 2 items. We have to join value back
var k = kvp[0];
kvp.shift();
var v = kvp.join("=");
kvp = [k, v];
var key = settings.encodeHTMLEntities ? htmlSpecialCharsEntityEncode(decodeURIComponent(kvp[0])) : decodeURIComponent(kvp[0]);
if (key) {
var value = settings.encodeHTMLEntities ? htmlSpecialCharsEntityEncode(decodeURIComponent(kvp[1])) : decodeURIComponent(kvp[1]);
formInnerHtml += '<input type="hidden" name="' + key + '" value="' + value + '" />';
}
});
}
if (isOtherMobileBrowser) {
$form = $("<form>").appendTo("body");
$form.hide()
.prop('method', settings.httpMethod)
.prop('action', fileUrl)
.html(formInnerHtml);
} else {
if (isIos) {
downloadWindow = window.open("about:blank");
downloadWindow.document.title = settings.popupWindowTitle;
formDoc = downloadWindow.document;
window.focus();
} else {
$iframe = $("<iframe style='display: none' src='about:blank'></iframe>").appendTo("body");
formDoc = getiframeDocument($iframe);
}
formDoc.write("<html><head></head><body><form method='" + settings.httpMethod + "' action='" + fileUrl + "'>" + formInnerHtml + "</form>" + settings.popupWindowTitle + "</body></html>");
$form = $(formDoc).find('form');
}
$form.submit();
}
//check if the file download has completed every checkInterval ms
setTimeout(checkFileDownloadComplete, settings.checkInterval);
function checkFileDownloadComplete() {
//has the cookie been written due to a file download occuring?
var cookieValue = settings.cookieValue;
if(typeof cookieValue == 'string') {
cookieValue = cookieValue.toLowerCase();
}
var lowerCaseCookie = settings.cookieName.toLowerCase() + "=" + cookieValue;
if (document.cookie.toLowerCase().indexOf(lowerCaseCookie) > -1) {
//execute specified callback
internalCallbacks.onSuccess(fileUrl);
//remove cookie
var cookieData = settings.cookieName + "=; path=" + settings.cookiePath + "; expires=" + new Date(0).toUTCString() + ";";
if (settings.cookieDomain) cookieData += " domain=" + settings.cookieDomain + ";";
document.cookie = cookieData;
//remove iframe
cleanUp(false);
return;
}
//has an error occured?
//if neither containers exist below then the file download is occuring on the current window
if (downloadWindow || $iframe) {
//has an error occured?
try {
var formDoc = downloadWindow ? downloadWindow.document : getiframeDocument($iframe);
if (formDoc && formDoc.body !== null && formDoc.body.innerHTML.length) {
var isFailure = true;
if ($form && $form.length) {
var $contents = $(formDoc.body).contents().first();
try {
if ($contents.length && $contents[0] === $form[0]) {
isFailure = false;
}
} catch (e) {
if (e && e.number == -2146828218) {
// IE 8-10 throw a permission denied after the form reloads on the "$contents[0] === $form[0]" comparison
isFailure = true;
} else {
throw e;
}
}
}
if (isFailure) {
// IE 8-10 don't always have the full content available right away, they need a litle bit to finish
setTimeout(function () {
internalCallbacks.onFail(formDoc.body.innerHTML, fileUrl);
cleanUp(true);
}, 100);
return;
}
}
}
catch (err) {
//500 error less than IE9
internalCallbacks.onFail('', fileUrl, err);
cleanUp(true);
return;
}
}
//keep checking...
setTimeout(checkFileDownloadComplete, settings.checkInterval);
}
//gets an iframes document in a cross browser compatible manner
function getiframeDocument($iframe) {
var iframeDoc = $iframe[0].contentWindow || $iframe[0].contentDocument;
if (iframeDoc.document) {
iframeDoc = iframeDoc.document;
}
return iframeDoc;
}
function cleanUp(isFailure) {
setTimeout(function() {
if (downloadWindow) {
if (isAndroid) {
downloadWindow.close();
}
if (isIos) {
if (downloadWindow.focus) {
downloadWindow.focus(); //ios safari bug doesn't allow a window to be closed unless it is focused
if (isFailure) {
downloadWindow.close();
}
}
}
}
//iframe cleanup appears to randomly cause the download to fail
//not doing it seems better than failure...
//if ($iframe) {
// $iframe.remove();
//}
}, 0);
}
function htmlSpecialCharsEntityEncode(str) {
return str.replace(htmlSpecialCharsRegEx, function(match) {
return '&' + htmlSpecialCharsPlaceHolders[match];
});
}
var promise = deferred.promise();
promise.abort = function() {
cleanUp();
$iframe.attr('src', '').html('');
internalCallbacks.onAbort(fileUrl);
};
return promise;
}
});
})(jQuery, this || window);