Problems avoiding the insertion of empty text fields into the sqlite database in Java

[Daniel Graham]

Hi. I have a form in my java inventory software that permits a shop manager to create new sales agents accounts.

It has 6 fields : firstNameField, lastNameField, dateOfBirthField, phoneNumberField, agentIDField, and agentPasswordField.
It also have a button called Add

This form stores its values in an SQLite database table called: sales_agents
Here's its schema:

CREATE TABLE `sales_agents` ( `firstName` varchar ( 20 ) NOT NULL, `lastName` varchar ( 20 ) NOT NULL, `dob` text, `phone` int ( 15 ) NOT NULL, `userType` varchar ( 25 ) NOT NULL, `userID` varchar ( 25 ) NOT NULL, `userPassword` varchar ( 20 ) NOT NULL CHECK(userPassword <> ' '), PRIMARY KEY(`userID`,`userPassword`) );

My goal is, when the manager clicks the Add button -- which is linked to a method called agentCreateBtnActionPerformed(), the following code should check that no field has been left blank,
before inserting anything to the database.
In case, there is an empty field, it prints out this message:

Please you are required to enter something in every empty field to carry out this operation!

in
a JOptionPane.

Here's the code:

private void agentCreateBtnActionPerformed(java.awt.event.ActionEvent evt) {                                               

        String fname = agentFirstName.getText();
        String lname = agentLastName.getText();

        String hisphone = agentPhone.getText();
        String hisid = agentUserID.getText();
        String pswd = String.valueOf(agentPassword.getPassword());

        if (!fname.equals("") || !lname.equals("") || agentDateOfBirth.getDate() != null
                || !hisphone.equals("") || !hisid.equals("") || !pswd.equals("")) {

            try {
                String sql = "insert into sales_agents values (?, ?, ?, ?, ?, ?, ?)";

                statement = conn.prepareStatement(sql);

                statement.setString(1, fname);
                statement.setString(2, lname);
                statement.setString(3, ((JTextComponent) agentDateOfBirth.getDateEditor().getUiComponent()).getText());
                statement.setString(4, hisphone);
                statement.setString(5, type);
                statement.setString(6, hisid);
                statement.setString(7, pswd);

                int rowsAffected = statement.executeUpdate();

                if (rowsAffected > 0) {
                    JOptionPane.showMessageDialog(this, "User created.");
                    clear();
                    setVisible(false);
                } else {
                    JOptionPane.showMessageDialog(this, "No rows Affected", "Error", JOptionPane.ERROR_MESSAGE);
                }
            } catch (SQLException ex) {
                JOptionPane.showMessageDialog(this, ex.getMessage(), "Error!", JOptionPane.WARNING_MESSAGE);
            }

        } else {

            JOptionPane.showMessageDialog(this,
                    "Please you are required to enter something in every empty field to carry out this operation!", "Warning!",
                    JOptionPane.ERROR_MESSAGE);

        }


    }                            

My Problem.
1) The above code keeps inserting empty strings when there are empty fields. And I've also realized that, when I insert something in the  agentPasswordField, and don't insert anything in the
agentIDField, and vice versa, it inserts both non-empty field values and empty field values to the database without popping up an error message.
Whereas, failing to insert into the agentIDField, and agentPasswordField generates an error message in JOptionPane that says:

A primary key constraint failed (UNIQUE constraint failed: sales_agents.userID, sales_agents.userPassword)

2) I added a check constraint to the userPasswordField thinking it would generate an SQLException, but it still did not work.

I've made a lot of research on this issue online but couldn't find something that helped.

Please, any help will be welcome.
regards

[Knute Snortum]

       if (!fname.equals("") || !lname.equals("") || agentDateOfBirth.getDate() != null                || !hisphone.equals("") || !hisid.equals("") || !pswd.equals("")) { Think carefully about the logic in this line.  Will you get to the "then" part only if all fields are filled?

Also, there is a method in the String object called isEmpty().  I would use that instead of equals("").

[Knute Snortum]

`userPassword`  varchar ( 20 ) NOT NULL CHECK(userPassword <> ' '), Is this literally what is in the CREATE TABLE definition?  It looks like the check is "not equal to one space".  Is that what you want?

[Dave Tolls]

Knute's spotted the immediate issue, but I have a question.
Why is your DOB column declared as TEXT rather than a DATE?
It looks like the source of the date of birth is already a date (maybe?)?