Post large amount of data with Wicket.ajax.post - ajax

Question

I'm trying to use the Behavior and JavaScript FileReader as can be seen in this question: Wicket Drag and drop functionality for adding an image
If I post more than 200k, I get an error Form too large. So perhaps I am missing some multipart stuff.
What is the proper way to call Wicket.ajax.post() with a large amount of data?
I tried setting mp to true, but then it started complaining that I do not have a form id. Does it need a form?
Btw. I use Jetty, but that has no problems using a regular file upload using forms.

Answer 1

This error comes from jetty Request implementation.
If you look at sources of the Request#extractFormParameters method, you will see next:
if (_context != null)
{
maxFormContentSize = _context.getContextHandler().getMaxFormContentSize();
maxFormKeys = _context.getContextHandler().getMaxFormKeys();
}
if (maxFormContentSize < 0)
{
Object obj = _channel.getServer().getAttribute("org.eclipse.jetty.server.Request.maxFormContentSize");
if (obj == null)
maxFormContentSize = 200000;
else if
...
}
So, in fact, you can really set your context values as pikand proposed as 0, or set server config as follows:
<Configure id="Server" class="org.eclipse.jetty.server.Server">
<Call name="setAttribute">
<Arg>org.eclipse.jetty.server.Request.maxFormContentSize</Arg>
<Arg>-1<!-- or 0, or any lt 0 --></Arg>
</Call>
...
</Configure>
Your exception is thrown a bit later according to this code:
if (contentLength > maxFormContentSize && maxFormContentSize > 0)
{
throw new IllegalStateException("Form too large: " + contentLength + " > " + maxFormContentSize);
}
So, you can see, that maxFormContentSize could be <= 0 not to throw this exception.
I think, there is no need to update something via ajax. But in fact it is better to limit data size, not to allow users put down your server.
Other application servers have their own settings, for most of them you should set maxPostSize value to zero, to disable this restriction.
Also, wicket Form component has it's own maxSize property, you can set it with Form#setMaxSize. The problem is that Form transmittes this value as Bytes value to FileUploadBase class, which has next javadoc:
The maximum size permitted for the complete request, as opposed to
fileSizeMax. A value of -1 indicates no maximum.
And actually this parameter is set via fileUpload.setSizeMax(maxSize.bytes());, and Bytes can't hold negative value. But I think you can try to set it as 0 and check if it works. By default, Form#getSizeMax() method checks:
return getApplication().getApplicationSettings().getDefaultMaximumUploadSize();
Which returns Bytes.MAX, which is equals to 8388608 terabytes. I think, this is about to be "no limit" value :)
Additionaly, as I know - you don't need to set Form id, to allow using multipart parameter. Only if you updating your form via ajax, you have to set Form.setOutputMarkupId(true). But actually, Form creates id by itself in renderHead method if it is multipart:
// register some metadata so we can later properly handle multipart ajax posts for
// embedded forms
registerJavaScriptNamespaces(response);
response
.render(JavaScriptHeaderItem.forScript("Wicket.Forms[\"" + getMarkupId()
+ "\"]={multipart:true};", Form.class.getName() + '.' + getMarkupId()
+ ".metadata"));
Note, that getMarkupId() method creates markup id if does not exists.

Answer 2

There is a form size limit in Jetty defaulting to 200k.
Add a jetty-web.xml in your webapp/WEB-INF folder. There you can set a form size limit of the needed size.
<?xml version="1.0"?>
<!DOCTYPE Configure PUBLIC "-//Mort Bay Consulting//DTD Configure//EN"
"http://jetty.mortbay.org/configure.dtd">
<Configure id="WebAppContext" class="org.eclipse.jetty.webapp.WebAppContext">
<Set name="maxFormContentSize" type="int">900000</Set>
<Set name="maxFormKeys">5000</Set>
</Configure>