Blob file download in Angular.js using $resource

<div ng-controller="appController" ng-app="app">

    <a ng-href="{{ fileUrl }}" download="file.txt">download</a>
</div>

var app = angular.module('app', []);

app.config(['$compileProvider', function ($compileProvider) {

    $compileProvider.aHrefSanitizationWhitelist(/^\s*(|blob|):/);

}]);

app.controller('appController', function ($scope, $window) {

    var data = 'some data here...',

        blob = new Blob([data], { type: 'text/plain' }),

        url = $window.URL || $window.webkitURL;

    $scope.fileUrl = url.createObjectURL(blob);

});

========================================================================================================

In this tutorial we will create a simple Angular application which can create a link of a downloadable file through $resource!

So first of all we will use XHR2 in order to use ArrayBuffer a new response type. Then we’ll use the HTML5 download attribute to name our blob file.

Let’s create our example resource called Email. Then add our custom action called getFile, in order to download the attached xlsx files.

	(function () {
	'use strict';
	angular
	.module('app')
	.factory('Email', Email);
	function Email($resource) {
	var url = 'emails/'
	, EmailBase;
	EmailBase = $resource(url + ':emailId', {emailId: '@id'}, {
	getFile: {
	method: 'GET',
	url: url + ':emailId/files/:fileName',
	params: {
	emailId: '@id',
	fileName: '@fileName'
	},
	cache: false
	}
	});
	return EmailBase;
	}
	}());

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Now extend it to be able to store the file in the memory. Here we have to set the sever’s responseType to ArrayBuffer. Here’s a catch: Angular can’t handle it so we have to transform the response.

All what we will do is turn the data into blob with the correct mime type.

	/* global Blob */
	(function () {
	'use strict';
	angular
	.module('app')
	.factory('Email', Email);
	function Email($resource) {
	var url = 'emails/'
	, EmailBase
	, xlsxContentType = 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet';
	EmailBase = $resource(url + ':emailId', {emailId: '@id'}, {
	getFile: {
	method: 'GET',
	url: url + ':emailId/files/:fileName',
	params: {
	emailId: '@id',
	fileName: '@fileName'
	},
	headers: {
	accept: xlsxContentType
	},
	responseType: 'arraybuffer',
	cache: false,
	transformResponse: function (data) {
	return {
	response: new Blob([data], {type: xlsxContentType})
	};
	}
	}
	});
	return EmailBase;
	}
	}());

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Let’s create our controller method. Here we create an url for the blob we got from our API.

	/* global URL */
	(function () {
	'use strict';
	angular
	.module('app')
	.controller('EmailCtrl', EmailCtrl);
	function EmailCtrl($scope, Email) {
	var vm = this
	, downloadableBlob = '';
	vm.getUploadedFileUrl = function getUploadedFileUrl() {
	return downloadableBlob;
	};
	$scope.$on('$stateChangeSuccess', updateDownloadableBlob);
	function updateDownloadableBlob() {
	Email
	.getFile({
	emailId: 1,
	fileName: 'some.xlsx'
	})
	.$promise
	.then(function (data) {
	downloadableBlob = URL.createObjectURL(data.response);
	});
	}
	}
	}());

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Model: done, ViewModel: done, view is the next. Here we’ll use another new feature in HTML5: the download attribute, which is used to force downloading instead of opening the file and be able to customise the name of the file. In our case it’s extremely important,
due to the blob file name is made up by a few random character. Also note target self, which is a little fix for some “browser’s”…

	<a target="_self" download="some.xlsx" ng-href="{{email.getUploadedFileUrl()}}">
	Download
	</a>

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At this point we could think: Yay! We made it! But it’s just not true. Angular adds an unsafe prefix to our URL due to security reasons against blob. So at the final step we have to disable this in a config method, by adding blob to the RegEx whitelist.

	(function () {
	'use strict';
	angular
	.module('app')
	.config(allowBlobLinkHrefs);
	function allowBlobLinkHrefs($compileProvider) {
	$compileProvider.aHrefSanitizationWhitelist(/^\s*(https?|ftp|mailto|tel|file|blob):/);
	}
	}());

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Thanks for reading! You can check out the final code below in a gist example with inlined angular code.

	<!doctype html>
	<html lang="en" data-ng-app='app' data-ng-controller="EmailCtrl as email">
	<head>
	<meta charset="UTF-8">
	<title>Example</title>
	<script src="https://cdnjs.cloudflare.com/ajax/libs/angular.js/1.4.3/angular.min.js"></script>
	<script>
	(function () {
	'use strict';
	angular
	.module('app')
	.config(allowBlobLinkHrefs)
	.controller('EmailCtrl', EmailCtrl)
	.factory('Email', Email);
	function Email($resource) {
	var url = 'emails/',
	EmailBase, xlsxContentType = 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet';
	EmailBase = $resource(url + ':emailId', {
	emailId: '@id'
	}, {
	getFile: {
	method: 'GET',
	url: url + ':emailId/files/:fileName',
	params: {
	emailId: '@id',
	fileName: '@fileName'
	},
	headers: {
	accept: xlsxContentType
	},
	responseType: 'arraybuffer',
	cache: false,
	transformResponse: function (data) {
	return {
	response: new Blob([data], {
	type: xlsxContentType
	})
	};
	}
	}
	});
	return EmailBase;
	}
	function EmailCtrl($scope, Email) {
	var vm = this,
	downloadableBlob = '';
	vm.getUploadedFileUrl = function getUploadedFileUrl() {
	return downloadableBlob;
	};
	$scope.$on('$stateChangeSuccess', updateDownloadableBlob);
	function updateDownloadableBlob() {
	Email
	.getFile({
	emailId: 1,
	fileName: 'some.xlsx'
	})
	.$promise
	.then(function (data) {
	downloadableBlob = URL.createObjectURL(data.response);
	});
	}
	}
	function allowBlobLinkHrefs($compileProvider) {
	$compileProvider.aHrefSanitizationWhitelist(/^\s*(https?|ftp|mailto|tel|file|blob):/);
	}
	}());
	</script>
	</head>
	<body>
	<a target="_self" download="some.xlsx" ng-href="{{email.getUploadedFileUrl()}}">
	Download
	</a>
	</body>
	</html>

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