FileUpload required =“ true”在PrimeFaces中不起作用

Question

I'm trying to put validation in my <p:fileUpload> . when the user upload without putting any file he get's an error message. I'm using mode="simple" and required="true" but required="true" doesn't work.

PS: I need to use mode="simple" because I need <p:commandButton> to submit other data.

<p:panelGrid columns="2">
    <h:outputLabel id="image" value="Select Image: *" />

    <p:fileUpload value="#{Jcalendar.file}" mode="simple"
                  allowTypes="/(\.|\/)(gif|jpe?g|png)$/"
                  required="true"
                  requiredMessage="File not selected !!"/>

    <f:facet name="footer">
        <p:commandButton value="Submit"
                         ajax="false"
                         action="#{Jcalendar.Upload}"
                         update=":form:msgs" />
    </f:facet>
</p:panelGrid>

Answer 1

As per the 5.2 source code, this will indeed fail when Servlet 3.0 native upload is being used instead of Apache Commons FileUpload.

The NativeFileUploadDecoder#decodeSimple() will only set the submitted value to an empty string when the input was not submitted at all. This will thus fail if the input is actually submitted, but with an empty value.

51        if(part != null) {
52            fileUpload.setTransient(true);
53            fileUpload.setSubmittedValue(new NativeUploadedFile(part));
54        }
55        else {
56            fileUpload.setSubmittedValue("");
57        }

The CommonsFileUploadDecoder#decodeSimple() will set the submitted value to an empty string when the submitted file name is empty, exactly as intented.

54        if(file != null) {
55            if(file.getName().equals("")) {
56                fileUpload.setSubmittedValue("");
57            } else {
58                fileUpload.setTransient(true);
59                fileUpload.setSubmittedValue(new DefaultUploadedFile(file));
60            }
61        }  

Your best bet to get it to work is to report an issue to PrimeFaces guys and in the meanwhile either customize/patch the renderer, or switch back to Commons uploader.