How to determine if resultset is empty?

Question

Good day!

I am wondering how can I get the desired result in my if-else statement if i want to determine if my search is existing or not. I do various combinations as suggested in the previous questions related to this but still I cannot get what I want.

Code 1: I cannot reach the else statement if my search is empty...

        if (resultSet!= null) {
            while (resultSet.next()) {   //MULTIPLE VALUE SEARCH
                Product product = new Product();
                product.setProductId(resultSet.getInt("productId"));
                product.setProductName(resultSet.getString("productName"));
                productList.add(product);
            }
            request.setAttribute("productList", productList);
            RequestDispatcher rd = request.getRequestDispatcher("adminViewSearch.jsp");
            rd.forward(request, response);
        } else {
            request.setAttribute("message", "Search Failed"):
            RequestDispatcher rd = request.getRequestDispatcher("adminViewSearch.jsp");
            rd.forward(request, response);
        }

Code 2: I cannot also reach the else statement where values searched should be displayed...

        if (!resultSet.next()) {
             .... Search Failed Message    
        } else { 
             while(result.next()){.....
        }

Code 3: Same result as Case 1:

        if (resultSet.wasNull()) {
             .... Search Failed Message    
        } else { 
             while(result.next()){.....
        }

I tried other combinations and still I cannot achieve the result I desired which is as follows: When the user search a value, if the resultset is null, an error message will appear, else if the search is not null, 1 or multiple searches will be displayed.

Kindly give me an alternative on how to this the easier way because it seems like I am doing it wrong.

Thank you in advance..

Solution 1

in code 1:

    if(productList.size() == 0 ){
         request.setAttribute("message", "Search Failed"):        
    }else{
          request.setAttribute("productList", productList);             
    }

    RequestDispatcher rd = request.getRequestDispatcher("adminViewSearch.jsp");
    rd.forward(request, response);  

---

Or more appropriate way would be just set

    if (resultSet!= null) {
        while (resultSet.next()) { 
            Product product = new Product();
            product.setProductId(resultSet.getInt("productId"));
            product.setProductName(resultSet.getString("productName"));
            productList.add(product);
        }
        request.setAttribute("productList", productList);
        RequestDispatcher rd = request.getRequestDispatcher("adminViewSearch.jsp");
        rd.forward(request, response);
    }

and on jsp

<c:if test="${fn:length(companies) gt 0}">
   <!--display collection using c:foreach -->
</c:if>

<c:if test="${fn:length(companies) eq 0}">
   Search failed
</c:if>

Solution 2

One possible, though not very elegant, solution is

if (!resultSet.next()) {
     .... Search Failed Message
} else {
    do {
        ...
    } while (resultSet.next());
}

However, if you need to populate a list anyway, perhaps Jigar Joshi's solution would be better.

Solution 3

Try this :

boolean searchEmpty = true;

while (resultSet.next()) {
  //create objects
  searchEmpty = false;
}

if (searchEmpty) {
 //set error message.
}

Solution 4

  if(rs !=null)
   {
    if(rs.isBeforeFirst() && rs.isAfetrLast())
     {
     out.println("row is empty");
      }
     else
    {
     while(rs.next())
     {

   //execute your code 
   }
 }
 }
else{ out.println("row is null");}

Solution 5

You can use ResultSet.getRow() which returns the number of rows and if it return zero than there are no products. And than you can carry out further operations.

View more solutions

Comments

[KNU]

as per my finding if (resultSet!= null) always evaluates to true and (always)enters the if block . Don't think it's a good way to determine if resultset is empty.

[Koray Tugay]

Javadoc says: "Retrieves the current row number. The first row is number 1, the second number 2, and so on."