Java JTable data from database

Question

I'm new to java and I need help with displaying a joined table/query in jtable.

First, I have done displaying data from 1 table which is:

• Select data from 1 table
• insert the result to its entity and insert each one of it to a List
• return the list to view and insert row to jtable

I am using a DAO pattern, which has a factory, interface, implement, entity and view.

So what if I select data from other table?

Here is my get method in implement for getting book

 public List get(String find) {
    try {
        ps = db.connect().prepareStatement("SELECT * FROM books WHERE title like ? ");
        ps.setString(1, "%" + find + "%");

        status = db.execute(ps);
        if (status) {
            books = db.get_result();
            listBooks = new ArrayList<>();

            while (books.next()) {
                entity_books b = new entity_books();
                b.setId(books.getInt(1));
                b.setId_category(books.getInt(2)); 
                b.setTitle(books.getString(3));
                listBooks.add(b);
            }
            books.close();
            return listBooks;
        }
    } catch (SQLException e) {
        System.out.println(e.getMessage());
    }
    return null;
}

and then in my view:

listBooks = booksDAO.get(find.getText());
    model = (DefaultTableModel) book_table.getModel();
    model.setRowCount(0);

    listBooks.forEach((data) -> {
        model.addRow(new Object[]{
            data.getId(),
            data.getId_category(),
            data.getTitle(),

        });
    });

This works fine, but I want the query to join table so I can see the category name instead of just ID category. I can do the query, but how do I apply that to my code?

Here is the query for joined table

select title,category from book b
join category c on c.id = b.id_category    

Normally if I select only 1 table, I would insert it to its entity ( book table -> book entity ), so how do I handle this with multiple tables?

Answer 1

I didn't use prepared statement, but this code works on my end.

String sql = "SELECT * FROM customer c JOIN company cmp ON c.company_idcompany = cmp.idcompany";

        ResultSet rs = stmt.executeQuery(sql);
        //STEP 5: Extract data from result set
        while (rs.next()) {
            //Retrieve this from customer table
            int id = rs.getInt("idcustomer");
            //Retrieve this from customer table
            String username = rs.getString("company_username");

            //Display values
            System.out.println("ID: " + id);
            System.out.println("Username: " + username);
        }