[FIXED] change type of List<String>

Issue

I want to insert the values of the products which are of type arrayList into the database but I'm getting this error "java.lang.String cannot be cast to model.Product". The problem is with the cast I did in servlet. this is its code:

String buyer = request.getParameter("buyer");
List<String> prodlist = Arrays.asList(request.getParameterValues("product"));

List<Product> prodmlist = (List<Product>) (List<?>) prodlist;
Bill bill = new Bill(buyer, prodmlist);
myDAO.add(bill);

and this is the method which will be populated

public static void add(Bill bill) {
Connection cnx;
    try {
    cnx = Connect.getConnection();
    String req = "insert into bil values (?,?)";
    PreparedStatement st = cnx.prepareStatement(req);
    st.setString(1, bill.getBuyer());
    for (Product prod : bill.getProduct()) {
        st.setString(2, prod.getName());
        st.addBatch(); // add the statement to the batch
    }
    st.executeUpdate();    
    cnx.commit();
}

Solution

In your code:

List<String> prodlist = Arrays.asList(request.getParameterValues("product"));
// Need to convert here...
List<Product> prodmlist = (List<Product>) (List<?>) prodlist;

You need to explicitly convert from List<String> to List<Product>. Do something along the lines of:

List<Product> products = new ArrayList<Product>();
for (String s: prodList){
    Product p = new Product();
    p.setName(s);
    products.add(p);
}

Now, I am making the assumption you have a setter to set the name on Product. It may be you have a constructor you can pass the name to (and save a line of code).

Answered By - David Brossard