primeface download not working

[Aurélien Peigney]

Hi, I tried to implement download but it does not work. I try to call "getFile" function but nothing happens.
Under form :

<p:commandButton value="Download the file" ajax="false" 
								icon="pi pi-arrow-down" styleClass="mr-2">
								<p:fileDownload value="#{mainController.getFile}" />
							</p:commandButton>

In my remote controller :

public StreamedContent getFile() {
		logger.info("get file 0");
		ByteArrayInputStream is = new ByteArrayInputStream(selectedDocument.getData());
		String guessContentTypeFromStream;
		try {
			guessContentTypeFromStream = URLConnection.guessContentTypeFromStream(is);
			file = new DefaultStreamedContent(is, guessContentTypeFromStream, "nomFicher.jpg");
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		logger.info("get file");
		return file;
	}

My log :

2023-11-07 06:50:48.005 DEBUG 32424 --- [nio-8080-exec-2] org.apache.tomcat.util.http.Parameters   : Start processing with input [javax.faces.partial.ajax=true&javax.faces.source=j_id_9%3Aj_id_f&primefaces.ignoreautoupdate=true&javax.faces.partial.execute=j_id_9%3Aj_id_f&javax.faces.partial.render=j_id_9%3Aj_id_f&j_id_9%3Aj_id_f=j_id_9%3Aj_id_f&j_id_9%3Aj_id_f_load=true&j_id_9_SUBMIT=1&javax.faces.ViewState=RThBQjZGMTcyMDdCMUNENjAwMDAwMDA0]
2023-11-07 06:50:48.023  WARN 32424 --- [nio-8080-exec-2] o.a.m.renderkit.html.HtmlLabelRenderer   : Attribute 'for' of label component with id j_id_9:modificationForm:outputlabelmember is not defined

Thanks for your responses

[Tim Holloway]

OK, first, I'm going to be pedantic.

Althouh apparently some IDEs will define JSF backing beans with names like "xxxController", JSF backing beans are not Controllers. They are Models.

You almost never create your own Controllers in JSF as they are pre-defined as part of JSF itself.

Now for your real problem. JSF uses JEE Expression Language to access (read OR write) properties of the backing beans. In many cases the same property may be read to display a control's value then written when the control's updated value is saved. That's the diffference between the "#" expression introducer commonly used by JSF and the "$" expression introducer used on JSPs. The "$" can only read, not write.

More importantly, that means that you access the property by the property name and not by the accessor method name, since either the "get" or "set" method could be required.

In short:

         <p:fileDownload value="#{mainController.file}" />

(Again, MainController isn't actually a Controller). When you coded #{mainController.getFile}, what JSF actually tried to invoke was the mainController bean's "getGetFile()" method, which, of course isn't what you wanted. JSF does not display errors if you get your names wrong, unfortunately, it just silently ignores the problem. There's a reason for that, I think. but I've never seen it formally stated.