JSF Datatable Binding not working properly - jsf

Question

I am creating a simple JSF application that is having only one JSP page (1 dropdown, 1 datatable & 1 submit button).
When i select the value from dropdown, i populate the table with an arraylist to display table data. The table is editable. Now when i click submit, i need to get the entire table into a list. For this i have used the binding attribute of datatable. But the issue is that null is returned from getValue.
Please help me with this issue as i have wasted lots of time.
class UserBean {
.....
private HtmlDataTable _dataTable;
public void setDataTable(HtmlDataTable dataTable)
{
this._dataTable = dataTable;
}
public HtmlDataTable getDataTable()
{
return _dataTable;
}
...................
public String submit() {
List<User> userDetails = (ArrayList<User>)((HtmlDataTable)getDataTable()).getValue();
System.out.println(userDetails);
return "";
}
}
// JSP Page
<h:dataTable id="erdatatable"
var="row" value="#{UserBean.userDetails}"
binding="#{UserBean.dataTable}">
....
</h:dataTable>
<h:commandButton value="Submit" action="#{UserBean.submit}"></h:commandButton>
// faces.config
<managed-bean>
<managed-bean-name>UserBean</managed-bean-name>
<managed-bean-class>com.datatable.UserBean</managed-bean-class>
<managed-bean-scope>request</managed-bean-scope>
</managed-bean>
// web.xml
<servlet>
<servlet-name>Faces Servlet</servlet-name>
<servlet-class>javax.faces.webapp.FacesServlet</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>Faces Servlet</servlet-name>
<url-pattern>/faces/*</url-pattern>
</servlet-mapping>

Answer 1

You can try changing managed-bean-scope to session. The request scope of the UserBean class ends when you invoke the action (dropdown select) and populates the datatable. When you press the submit button again, a new instance of UserBean is created.

Answer 2

If you only need the data from the table, you don't need (and probably shouldn't) bind it at all. Your userDetails will contain all the data, as edited by the user, without any extra work.
If you use the session scope, you will have bugs as soon as someone opens your application in two tabs, chooses something from the dropdown on one of them and then presses the button on the second one. A common solution is to use view scope (which does not work well with binding, but - as I stated - you should not have used it at all)