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New to javascript, having trouble figuring this out, help!
I am trying to use the Javascript FileReader API to read files to upload to a server. So far, it works great for text files.
When I try to upload binary files, such as image/.doc, the files seem to be corrupted, and do not open.
Using dojo on the client side, and java on the server side, with dwr to handle remote method calls. Code :
Using a html file input, so a user can select multiple files to upload at once :
<input type="file" id="fileInput" multiple>
And the javascript code which reads the file content:
uploadFiles: function(eve) {
var fileContent = null;
for(var i = 0; i < this.filesToBeUploaded.length; i++){
var reader = new FileReader();
reader.onload = (function(fileToBeUploaded) {
return function(e) {
fileContent = e.target.result;
// fileContent object contains the content of the read file
};
})(this.filesToBeUploaded[i]);
reader.readAsBinaryString(this.filesToBeUploaded[i]);
}
}
The fileContent object will be sent as a parameter to a java method, which will write the file.
public boolean uploadFile(String fileName, String fileContent) {
try {
File file = new File("/home/user/files/" + fileName);
FileOutputStream outputStream = new FileOutputStream(file);
outputStream.write(fileContent.getBytes());
outputStream.close();
} catch (FileNotFoundException ex) {
logger.error("Error uploading files: ", ex);
return false;
} catch (IOException ioe) {
logger.error("Error uploading files: ", ioe);
return false;
}
return true;
}
I have read some answers suggesting the use of xhr and servlets to achieve this.
Is there a way to use FileReader, so that it can read files of any type (text, image, excel etc.) ?
I have tried using reader.readAsBinaryString() and reader.readAsDataUrl() (Decoded the base64 fileContent before writing to a file), but they did not seem to work.
PS :
1. Also tried reader.readAsArrayBuffer(), the resultant ArrayBuffer object shows some byteLength, but no content, and when this is passed to the server, all I see is {}.
548
Thanks N.M! So, it looks like ArrayBuffer objects cannot be used directly, and a DataView must be created in order to use them. Below is what worked -
uploadFiles: function(eve) {
var fileContent = null;
for(var i = 0; i < this.filesToBeUploaded.length; i++){
var reader = new FileReader();
reader.onload = (function(fileToBeUploaded) {
return function(e) {
fileContent = e.target.result;
var int8View = new Int8Array(fileContent);
// now int8View object has the content of the read file!
};
})(this.filesToBeUploaded[i]);
reader.readAsArrayBuffer(this.filesToBeUploaded[i]);
}
}
Refer N.M 's comments to the question for links to the relevant pages.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Typed_arrays
86
example
<html>
<head>
<link rel="stylesheet" href="http://code.jquery.com/ui/1.11.3/themes/smoothness/jquery-ui.css">
<script src="http://code.jquery.com/jquery-1.10.2.js"></script>
<script src="http://code.jquery.com/ui/1.11.3/jquery-ui.js"></script>
</head>
<body>
<script>
function PreviewImage() {
var oFReader = new FileReader();
oFReader.readAsDataURL(document.getElementById("uploadImage").files[0]);
oFReader.onload = function (oFREvent) {
var sizef = document.getElementById('uploadImage').files[0].size;
document.getElementById("uploadPreview").src = oFREvent.target.result;
document.getElementById("uploadImageValue").value = oFREvent.target.result;
};
};
jQuery(document).ready(function(){
$('#viewSource').click(function ()
{
var imgUrl = $('#uploadImageValue').val();
alert(imgUrl);
//here ajax
});
});
</script>
<div>
<input type="hidden" id="uploadImageValue" name="uploadImageValue" value="" />
<img id="uploadPreview" style="width: 150px; height: 150px;" /><br />
<input id="uploadImage" style="width:120px" type="file" size="10" accept="image/jpeg,image/gif, image/png" name="myPhoto" onchange="PreviewImage();" />
</div>
<a href="#" id="viewSource">Source file</a>
</body>
</html>
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