NullPointerException when executing same action multiple times - jsf

Question

In my xhtml page, I have a search button and a p:datatable to display the search results. I added a c:if condition to hide and display the datatable.
<c:if test="#{!search_bean.isResultList}">
In my managedBean, I created the flag isResultEmpty and set it to true in my doInit(). In the action of my search button (actSearchForData), I've set it to true if my List is not empty.
private String actSearchForData() throws Exception {
if(resultList.size > 0) {
isResultEmpty = false;
}
}
Now this works without any errors the first time I execute actSearchForData and my resultList is displayed. But when I try to run actSearchForData the second time, I encounter nullpointer exception. I've tried debugging by returning isResultEmpty = true after getting the resultList but this only causes my flag to always return isResultEmpty = true.
How can I execute my search function multiple times and display the results in the datatable without getting any nullpointer exceptions?
UPDATE: I've tried using render again this time for the flag like rendered="!#{search_bean.isResultEmpty}". I no longer get nullpointerexception and my result list count displays the correct number of results but my data table does not show.

Answer 1

The JSF way to control conditional rendering is to use the rendered attribute like
<p:dataTable id="..."
value="#{search_bean.resultList}"
var="..."
rendered="#{not empty search_bean.resultList}" />
This will not render the datatable if resultList is null or resultList.size() is 0.

Answer 2

you must be getting NullPointerException (maybe) - because your "resultList" is null and still you are executing "resultList.size" inside "if(..)" statement
try something like This...
private String actSearchForData() {
if(resultList==null || resultList.size>0) {
isResultEmpty=false;
}
}
This code executes "isResultEmpty=false" - if(resultList is null)
Hope this works for you...