invoke confirmDialog in bean - jsf-2

Question

I use Primefaces 5.1 with JSF 2.2.6.
i need identify if one file already exists in folder when user fileupload (primefaces).
I have a class that uses PrimeFaces which uploads user files to a particular folder, but if the user attempts to upload a file with the same name as one that is already present i need alert and cancel the handler.
Any idea?
the code in xhtml is:
<h:form enctype="multipart/form-data" id="addFileDialog">
<p:fileUpload fileUploadListener="#{attachmentsComponent.handleFileUpload}"
mode="advanced" multiple="true" dragDropSupport="true"
label="#{text['tasksbacking.addFile.choose']}" uploadLabel="#{text['tasksbacking.addFile.upload']}" cancelLabel="#{text['tasksbacking.addFile.cancel']}"
allowTypes="/(\.|\/)(gif|jpe?g|png|pdf|doc|docx|txt|xml)$/" invalidFileMessage="#{text['tasksbacking.addFile.invalidFile']}"
fileLimit="4" fileLimitMessage="#{text['tasksbacking.addFile.invalidCount']}"
oncomplete="PF('addfile').hide();"/>
</h:form>
the code in bean is:
public void handleFileUpload(FileUploadEvent event) {
// vars
String originalName = event.getFile().getFileName();
if (log.isDebugEnabled()) {
log.debug("create file: " + originalName);
}
User loggedInUser = getSessionUser();
// define parent folder
Folder folder = null;
// versionamento
FileDetail fileDTSVersion = null;
// verifica se ficheiro já existe na folder
if (this.selectedNodeAttach != null) {
if (this.selectedNodeAttach.getData() instanceof Attachment) {
folder = (Folder) (this.selectedNodeAttach.getParent().getData());
} else {
folder = (Folder) (this.selectedNodeAttach.getData());
}
for (TreeNode tree : this.selectedNodeAttach.getChildren()) {
if (tree.getType().equals("file")) {
Attachment fileChild = this.attachmentManager.initializeAttachment((Attachment) (tree.getData()));
if (fileChild.getName().equals(originalName)) {
if (fileChild.getContentObject() instanceof File) {
//file already exists --- need confirm action ???????????
}
}
}
}
}
// guarda ficheiro localmente
try {
if (log.isDebugEnabled()) {
log.debug("saving file in local..." + internalName);
}
copyFileToDisk(internalName, event.getFile().getInputstream());
} catch (IOException ex) {
log.error(null, ex);
}
}

Answer 1

You can achieve that by first defining a <p:confirmDialog/> in your XHTML and showing it with your Managed Bean by sending a JS through the Request Context, like so:
XHTML:
<p:confirmDialog widgetVar="dialog" appendToBody="true" header="Erro!"/>
Controller:
RequestContext.getCurrentInstance().execute("PF('dialog').show();")
By the way, there is already another question just like yours. Remember to search before posting a new question.
Calling Primefaces dialog box from Managed Bean function