How can I insert and delete value in a database in derby in JSP?

Question

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The problem is I cannot delete customer from the database. I can create a new customer, but if I leave blank the fields it create an empty record in

Answer 1

I understand from the previous question where you defined ID as integer, so you should use setInt instead of setString, try as

public void deleteClient(Integer id){

    try {

        createConnection();
        String delete="DELETE FROM CUSTOMER WHERE ID=?";
        PreparedStatement ps=conn.prepareStatement(delete);
        ps.setInt(1, id);
        ps.executeUpdate();
    } catch (Exception e) {
        e.printStackTrace();
    }finally {
        ps.close();
        closeConnection();
    }
}

Id is an integer in the database field where you defined it has a primary key.

Update 1

Use the following in your index.jsp to convert String to int, pass idNum to your method.

 Integer idNum = null;
 String id = request.getParameter("ID");
    if(id != null) {
        try {
            System.out.println("String Id value --> "+id.trim());
            idNum = Integer.parseInt(id.trim());
        }
        catch(NumberFormatException ex) {
            ex.printStackTrace();
        }
    }