jComboBox Instead of category name add category ID into the database in java netbeans

Programmer Hari :

i am creating a small inventory control system for my final year. instead of add category name add category id in to the database i don't know how add do the task .what i tried so far i attached.

i load the category in to jComboBox1

 public void LoadCategory()
    {
            try {
                Class.forName("com.mysql.jdbc.Driver");
                con1 = DriverManager.getConnection("jdbc:mysql://localhost/javapos","root","");
                insert = con1.prepareStatement("SELECT * FROM category");
                 ResultSet rs = insert.executeQuery();
                 jComboBox1.removeAllItems();
                 while(rs.next())
                 {
                     jComboBox1.addItem(rs.getString(2));
                 }

            } 
            catch (Exception e) {
            }
    }

add the record into the product table.

String productname =txtproduct.getText();
     String productdec =txtdec.getText();
     int categoryid =jComboBox1.getSelectedItem().toString();

     Class.forName("com.mysql.jdbc.Driver");
                con1 = DriverManager.getConnection("jdbc:mysql://localhost/javapos","root","");

    insert = con1.prepareStatement("insert into product (productname,description,category)values(?,?,?)");
     insert.setString(1,productname);
     insert.setString(2,productdec);
     insert.setString(3,categoryid);
     insert.executeUpdate();
     JOptionPane.showMessageDialog(this, "Sucsessfully Saved");

Alexander Chernin :

I guess (from your question) your table category should contains such columns:

• id - int autoincremented (implicit)
• productname - ...
• description - ...
• name - name of a category

Next. You need to create a custom JComboBox item's type. For the example:

class CategoryItem
{
    int id;
    String name;

    // add other fields if you want...

    CategoryItem(int id, String name)
    {
        this.id = id;
        this.name = name;
    }
    String toString()
    {
        return name;
    }
}

When you're loading the records from the table you're creating the CategoryItem class objects and append them to JComboBox, like this:

public void LoadCategory()
{
    //...
    jComboBox1.removeAllItems();
    while(rs.next())
    {
        // rs.getInt('id') - id value of the category record
        jComboBox1.addItem( CategoryItem( rs.getInt('id'), rs.getString('name') );
    }
     //...
}

When a new record to be inserted into the table the database set and fill its id with a new autoincremented value implicitly:

Category categoryItem = (CategoryItem)jComboBox1.getSelectedItem();

insert = con1.prepareStatement("INSERT INTO product (productname, description, name) VALUES (?,?,?)");

insert.setString(1, productname);
insert.setString(2, productdec);
insert.setString(3, categoryItem.name);

To get the last record create a query (example for MySQL):

getLastCategory.prepareStatement("SELECT * FROM category WHERE id = LAST_INSERT_ID()");

If you need to update the category's data you get CategoryItem object and take its id:

CategoryItem item = (CategoryItem)jComboBox1.getSelectedItem();
int id = item.id;

query.prepareStaement("UPDATE category SET productname = ? WHERE id = ?");
query.setString(1, "new product name");
query.setInt(2, id);