JSF Interview Questions and Answers
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Ques 16. How to terminate the session?
In order to terminate the session you can use session invalidate method.
This is an example how to terminate the session from the action method of a backing bean:
public String logout() {
FacesContext fc = FacesContext.getCurrentInstance();
HttpSession session = (HttpSession) fc.getExternalContext().getSession(false);
session.invalidate();
return "login_page";
}
The following code snippet allows to terminate the session from the jsp page:
<% session.invalidate(); %>
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Ques 17. How to reload the page after ValueChangeListener is invoked?
At the end of the ValueChangeListener, call FacesContext.getCurrentInstance().renderResponse()
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Ques 18. How to download PDF file with JSF?
This is an code example how it can be done with action listener of the backing bean.
Add the following method to the backing bean:
public void viewPdf(ActionEvent event) {
String filename = "filename.pdf";
// use your own method that reads file to the byte array
byte[] pdf = getTheContentOfTheFile(filename);
FacesContext faces = FacesContext.getCurrentInstance();
HttpServletResponse response = (HttpServletResponse) faces.getExternalContext().getResponse();
response.setContentType("application/pdf");
response.setContentLength(pdf.length);
response.setHeader( "Content-disposition", "inline; filename=""+fileName+""");
try {
ServletOutputStream out;
out = response.getOutputStream();
out.write(pdf);
} catch (IOException e) {
e.printStackTrace();
}
faces.responseComplete();
}
This is a jsp file snippet:
<h:commandButton immediate="true" actionListener="#{backingBean.viewPdf}" value="Read PDF" />
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Ques 19. How to show Confirmation Dialog when user Click the Command Link?
ah:commandLink assign the onclick attribute for internal use. So, you cannot use it to write your own code. This problem will fixed in the JSF 1.2. For the current JSF version you can use onmousedown event that occurs before onclick.
<script language="javascript">
function ConfirmDelete(link) {
var delete = confirm('Do you want to Delete?');
if (delete == true) {
link.onclick();
}
}
</script>
. . . . <h:commandLink action="delete" onmousedown="return ConfirmDelete(this);">
<h:outputText value="delete it"/> </h:commandLink>
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Ques 20. What is the different between getRequestParameterMap() and getRequestParameterValuesMap()
getRequestParameterValuesMap() similar to getRequestParameterMap(), but contains multiple values for for the parameters with the same name. It is important if you one of the components such as <h:selectMany>.
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