JSF selectOneMenu onChange to update an object

I used the code from the answer in <https://stackoverflow.com/questions/16207479/how-to-include-file-from-external-local-disk-file-system-folder-in-jsf> to come up with:

JSF

...
<ui:define name = "content">
    <h:form> 
        <span class="dataSpan" style="border-width:0px">
            <object id="thePdf" data="#{request.contextPath}/my.pdf" type="application/pdf" width="1150" height="620">
                <a href="#{request.contextPath}/my.pdf">Download file.pdf</a>
            </object>
        </span>
    </h:form>
            
    <h:form class="standardFont">  
        <span class="notesSpan" style="border-width:0px">
            <p:panel header="Data Entry">
                        
                <h:panelGrid columns="1" border="0" styleClass="form-grid" columnClasses="form-column-label,form-column-input">

                <h:outputLabel />
                <h:outputLabel id="fileName" styleClass="centerBoldRed" value="#{pdfServlet.fileName}" >
                </h:outputLabel>
                <h:outputLabel />
                <h:outputLabel for="fileNameList">Files:</h:outputLabel>
                <h:selectOneMenu id="fileNameList" value="#{dataEntryBean.fileNameList}" styleClass="boldRed">
                    <f:selectItems value="#{dataEntryBean.fileNameList}" var="file" itemValue="#{file}" itemLabel="#{file}" />
                </h:selectOneMenu>                          
                <h:message class="error" for="fileNameList" id="fileNameListError" />

                </h:panelGrid>
...

Java - PdfServlet

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
        String s = "my.pdf";
        File file = new File("//Temp/input/my/pdfs/IncomingPdf/" + s);
        response.setHeader("Content-Type", getServletContext().getMimeType(file.getName()));
        response.setHeader("Content-Length", String.valueOf(file.length()));
        response.setHeader("Content-Disposition", "inline; filename=\"" + file.getName()+ "\"");
        Files.copy(file.toPath(), response.getOutputStream());
    }

DataEntryBean

...
    public List<String> getFileNameList() {
        return fileNameList;
    }

    public final void setFileNameList() {
                
        File folder = new File("//Temp/input/my/pdfs/IncomingPdf/");
        FilenameFilter pdfFileFilter = (File dir, String name) -> {
            return name.endsWith(".pdf");
        };

        File[] files = folder.listFiles(pdfFileFilter);
        try {
            for(File f : files) {
                fileNameList.add(f.getName());
            }
        } catch (ArrayIndexOutOfBoundsException ex) {
            fileNameList.add("No PDF file was found.");
        }
    }       
...

And this works great. The PDF file is opened in the viewer and the selectOneMenu displays all of the file names from the directory.

So my question is this:
How can I change/select a name from the selectOneMenu and have that file get opened in the object?

I think I have to use the itemValue from the selectOneMenu as a parameter to PdfServlet and use that instead of the hardcoded value in s but I'm not sure how to do that. Any suggestions would be appreciated. TIA.

So here's what I did...not sure if it's the correct way, but it does what I was looking for...

Added to JSF (at top):

<f:metadata>
    <f:viewAction action="#{dataEntryBean.onLoad()}" />
    <f:viewAction action="#{pdfServlet.setFileName(dataEntryBean.fileName)}" />
</f:metadata>		

And added this before fileNameListError:

<h:commandButton value="Submit" action="#pdfServlet.setFileName(dataEntryBean.fileName)}"/>

Then in PdfServlet I changed

String s = "my.pdf";

to

private static String s;

Added to DataEntryBean:

    public void onLoad() {
        setFileNameList();
        this.fileName = this.fileNameList.get(0);
    }

As I said, I'm not sure if this is the 100% correct way to do this but it does work. Any updates or corrections that make this better would be appreciated. Thanks.