How can I effectively handle MaxUploadSizeExceededException in an ajax based file uploading operation.
I have an ajax based file upload functionality. I need to handle the MaxUploadSizeExceededException when user upload a file whose size exceeds the maximum allowed. I got the solution from here, where user will be directed to a error page, when file size exceeds. Since I am using ajax request to upload file, I want to show a javascript alert in the browser when file size exceeds, instead of redirecting to some error page.
How can I do this ?
A possible solution would be to completely follow the solution in your linked answer, where, on exception you would redirect to an error.jsp, which would in fact return JSON, so as simple as
error.jsp
<%# page contentType="application/json;charset=UTF-8" language="java" %>
{"errors":"${errors}"}
in which case the success part of your ajax call would be
success : function(json) {
alert(json.errors);
}
I don't know in Ajax, since you asked to show using javascript ,You can use ActiveXObject if you are using browsers that doesn't support HTML 5. If you are using modern browsers, you can use File APIs like below,
$('#fileId').bind('change', function() {
//The below code will get the size of the uploaded file.
alert(this.files[0].size);
});
You will get the file size in bytes, you can divide the file size by 1024 for getting in kb.
Related
Can I send a file as multipart by XMLHttpRequest to a servlet?
I am making a form and submitting it as multipart, but somehow I am not getting a response for successfully uploading it. I do not want the page to be refreshed, so it has to take place by Ajax.
That's only possible with the XHR FormData API (previously known being part of as "XHR2" or "XHR Level 2", currently known as "XHR Advanced Features").
Given this HTML,
<input type="file" id="myFileField" name="myFile" />
you can upload it as below:
var formData = new FormData();
formData.append("myFile", document.getElementById("myFileField").files[0]);
var xhr = new XMLHttpRequest();
xhr.open("POST", "myServletUrl");
xhr.send(formData);
XHR will take care about proper headers and request body encoding and the file will in this example be available on the server side as form-data part with the name myFile.
You need to keep in mind that FormData API is not supported in older browsers. At caniuse.com you can see that it's currently implemented in Chrome 7+, Firefox 3.5+, Safari 5+, Internet Explorer 10+ and Opera 12+.
In case you're using jQuery, then you might be tempted to use its $.val() function as below:
formData.append("myFile", $("#myFileField").val());
But this is incorrect as it doesn't return the whole File object, but merely the file name as String which is utterly useless as it doesn't contain the file contents.
If you don't want to use document.getElementById() for some reason, then use one of the following instead:
formData.append("myFile", $("#myFileField").prop("files")[0]);
formData.append("myFile", $("#myFileField")[0].files[0]);
An alternative is to use the jQuery Form plugin. Your entire form, when written and functioning properly without any line of JavaScript code, will then instantly be ajaxified with just the following line:
$("#formId").ajaxForm(function(response) {
// Handle Ajax response here.
});
It also supports file uploads as well by a hidden iframe trick. See also this jQuery Form documentation for an in-depth explanation. You may only need to change the servlet code to be able to intercept on both normal (synchronous) and Ajax (asynchronous) requests. See also this answer for a concrete example: Simple calculator with JSP/Servlet and Ajax
Either way, the uploaded file should then be available in the doPost() method of a #MultipartConfig servlet as follows:
Part myFile = request.getPart("myFile");
Or if you're still on Servlet 2.5 or older, use Apache Commons FileUpload the usual way. See also this answer for a concrete example: How can I upload files to a server using JSP/Servlet?
It's not possible to send multipart/form-data with XMLHttpRequest (though it is possible in modern browsers, with XHR2. See BalusC's answer).
A common way to achieve what you want is to use a regular form, but in an iframe instead. This way, only the iframe is refreshed on upload.
In my application, user confirms and a jsp page is loaded with confirmation details. I need to email that confirmation.jsp page in the same format.
I tried doing it as below:
In JSP page, surrounded the Body with <div id='content'>
and then through a load function, sent the contents of the page through request paramater:
function load(){
document.getElementById("emailbody").value=encodeURIComponent(document.getElementById('content').innerHTML);
}
But the issue is, the page format has changed and it is not in a HTML format (not at all in readable format).
In your case you should try sending mail on server side in a background thread so that your jsp rendering is not delayed. There are useful server side temlating engines like velocity which can help you achieve your tarhet html and would be easy to send then.
Can I send an entire HTML page with an AJAX response? If so, how to render that HTML page and what are the pros and cons doing that. The reason why I am asking this question is I found out that if we use response.sendRedirect("index.html") as a reply to an AJAX request in servlet we get the indx.html as AJAX response XML.
Your question doesn't make much sense and I can't quite tell what you're asking - the response to an ajax request will be whatever the server sends back. It could be plain text, XML, HTML, a fragment of an HTML/XML document etc. What you can do with depends on your script. If you're using a library like jQuery, what happens on the client side and what you can do with the response can also depend on how the library interprets the response (Is it a script? It it HTML/XML or JSON?).
if we use response.sendRedirect("index.html") as a reply to ajax request in servlet we get the indx.html as ajax response xml. Can some one pls explain this
An ajax request will behave much like a 'regular' HTTP request. So when you send back a redirect from your server (HTTPServletResponse#sendRedirect), the browser follows the redirect just like it would for any other request. If your ajax request was to a resource that required HTTP BASIC authentication, you'd see a prompt to login, just like you would if you visited the URL directly in a new browser window.
If you want to send HTML as a response, because you want to update divs, tables or other elements, but still want to use the same css or javascript files then it can make sense.
What you can do is to just send it as plain/text back to the javascript function, it can then take that and put it into the inner html element that you want to replace, but, don't do this if you want to replace the entire page, then doing what you want is pointless.
When you make the http request for your ajax call, it has its own response stream, and so when you redirect you are just telling the browser to have that http request go to index.html, as #no.good.at.coding mentioned.
If I get your question, you just want to know whether you could return whole entire HTML with AJAX and know the pro and cons.
The short answer to your question is yes, you could return the entire HTML page with your AJAX response as AJAX is just an http request to the server.
Why would you want to get the entire HTML? That's confusing to me and that is the part that I am not clear about. If you want to want to render the entire HTML (including tags like html, body, etc?), you might as well open it as a new page instead of calling it via Ajax.
If you are saying that you only want to get fragments of HTML to populate a placeholder in your page via AJAX then this is an acceptable practice. jQuery even provides load() function (http://api.jquery.com/load/) to make that task easy for you to use (check the section Loading Page Fragments).
Using this method, you could populate the placeholder using the HTML Fragments that is dictated by your server logic (i.e when the login fails or succeed) including the one via server redirect in your question.
1) In my servlet program, I have a statement which will be printed using the code as follows,
out.println("<b>This is servlet output</b>");
Instead of getting printed in bold, it just gets printed with the tag in the broswer itself.
How to rectify the same?
2) Also, in the servlet page after the submission of a jsp form, I want to add the below HTML tag inside the java code of the servlet program.
Go to JSP form
How to achieve the same? Please advise.
1) The browser is interpreting your output like text, try adding
response.setContentType("text/html");
This line tells the browser that you're sending HTML and that it should be interpreted that way.
2) The same as bold text
out.println("Go to JSP form");
On a related note, I'd suggest that none of your Servlet class directly write HTML content to the response page. Servlet are made to handle forms, and aren't easy to use when it comes to write HTML responses.
Once thing you can try is to write the response in a JSP page, then forwarding the request to the JSP so it can handle user output.
Here is a sample:
1) servet_output.jsp
<b>My bold test</b>
Go to JSP form
2) Your servlet redirects to the JSP page:
request.getRequestDispatcher("servlet_output.jsp").forward(request, response);
This way, your servlet handles the request, and the JSP takes care of writing the response to the browser.
Don't use servlets for html.jsp is the right place to use that.
just use
request.getRequestDispatcher("name.jsp").forward(request, response);
and write html code there.
This question already has answers here:
How to retrieve and display images from a database in a JSP page?
(6 answers)
Closed 7 years ago.
I currently have to generate an image that displays the text of a string, i need to make this image on a Servlet and then somehow pass the image to a JSP page so that it can display it. I'm trying to avoid saving the image, and instead somehow stream the image to the JSP.
I haven't found a way of generating the image since i started with finding how to pass an image from the Servlet to the JSP adn got stuck.
EDIT:
The jsp page is already made and isn't created by the servlet, i have to pass the image into an already existing jsp
Any help is appreciated.
You need to write the image as a byte array to the response's output stream. Something like this:
byte[] imageBytes = getImageAsBytes();
response.setContentType("image/jpeg");
response.setContentLength(imageBytes.length);
response.getOutputStream().write(imageBytes);
Then in you JSP you just use a standard img element:
<img src="url to your servlet">
You can't1 return both in the same response, since you're returning different types (an HTML page of type text/html and an image of type image/jpeg, say).
For this sort of thing, I will generate the image during the initial servlet request (for the containing HTML page). I store it in a cache in my servlet, and write the HTML page with the image tag containing a URL to that image with the handle.
e.g. the browser asks for http://whatever/page
The servlet generates the image, and writes an HTML tag in the page like
<img src="http://whatever/image/unique_handle_to_image">
The browser will render the HTML page, and as part of that issue a new request to my servlet with the handle for the image.
e.g. the browser now asks for http://whatever/image/unique_handle_to_image
I then return the image as content type image/jpeg or similar.
So you have two requests going on. One for the page, in which you render the image and store it temporarily, and the second in which you return the image. You have to remember to clear the image cache, but that's all straightforward. I wouldn't worry about storing lots of images, since the two requests from the browser usually (!) come in quick succession.
I guess it's possible to use a data uri provided your browser supports it, and create something like
<img src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAYAAACNMs+9AAAABGdBTUEAALGPC/xhBQAAAAlwSFlzAAALEwAACxMBAJqcGAAAAAd0SU1FB9YGARc5KB0XV+IAAAAddEVYdENvbW1lbnQAQ3JlYXRlZCB3aXRoIFRoZSBHSU1Q72QlbgAAAF1JREFUGNO9zL0NglAAxPEfdLTs4BZM4DIO4C7OwQg2JoQ9LE1exdlYvBBeZ7jqch9//q1uH4TLzw4d6+ErXMMcXuHWxId3KOETnnXXV6MJpcq2MLaI97CER3N0vr4MkhoXe0rZigAAAABJRU5ErkJggg==" alt="Red dot" />
Note there are a number of caveats surrounding these. See the linked page.
I would do something along this lines to achieve this:
On the JSP page you put a link to an image:
<img src="servlet/path?word=value">the rest</img>
This link points to your servlet, it generates image using request parameters, you do not need to save it, just put it right into response's output stream. You have to remember to disable browser caching for this servlet.
JSP page is displayed first, next all the images are requested, it should work just fine.
Of course, you should not put the text to display in a parameter like this, you should propably encipher it somehow or store it in a HTTP session.
Hope this helps.
If I understand your problem correctly, the sequence of events will be:
You generate an HTML page;
That HTML page is sent to the client; and
The client's browser reads the image URL and requests it as a separate request.
So, you can't generate the image and pass it to the JSP. You can however generate a URL to get the image and put that in the JSP. That's easy enough to pass by the servlet putting it on the HttpServletRequest object (request scope in JSP). For example, generate:
<a href="http://myhost.com/image_servlet?id=1234"/>
You don't really say what that text is or what information is required to generate the image. If you can't encapsulate that in a GET URL, you may need to add extra information and put it in the HttpSession so it can be retrieved on the next get image request.
...
response.setContentType("image/jpeg");
response.setContentLength(imageBytes.length); // imageBytes - image in bytes
response.getOutputStream().write(imageBytes);//
outStream.flush();
outStream.close();