problem with java.lang.NullPointerException

Well, I'm trying to populate a JTable with database data, but I've always encountered the same exception as java.lang.NullPointerException.

It should work as follows:

user clicks the refresh button and the program pulls the DB information, then allocates them to a table.

Note: I already managed to use this code in another program and it worked without errors.

  

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException       at DAO.documentoDAO.SelectFull (documentDAO.java:39)       at View.cadastro_documento $ 3.actionPerformed (cadastro_documento.java:115)

These are the classes I've created

  

file_document

package View;

import java.awt.BorderLayout;
import java.awt.EventQueue;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.JTable;
import javax.swing.table.DefaultTableModel;

import DAO.UsuarioDAO;
import DAO.documentoDAO;
import Model.Usuario;
import Model.documento;

import javax.swing.JButton;
import javax.swing.JMenuBar;
import javax.swing.JMenu;
import javax.swing.JMenuItem;
import java.awt.event.ActionListener;
import java.util.List;
import java.awt.event.ActionEvent;

public class cadastro_documento extends JFrame {

    private JPanel contentPane;
    private JTextField textField;
    private JTable table;

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    cadastro_documento frame = new cadastro_documento();
                    frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the frame.
     */
    public cadastro_documento() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setBounds(100, 100, 450, 300);

        JMenuBar menuBar = new JMenuBar();
        setJMenuBar(menuBar);

        JMenu mnArquivos = new JMenu("Arquivos");
        menuBar.add(mnArquivos);

        JMenuItem mntmSair = new JMenuItem("Sair");
        mntmSair.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                menu menu = new menu();
                menu.setVisible(true);
                dispose();
            }
        });
        mnArquivos.add(mntmSair);
        contentPane = new JPanel();
        contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
        setContentPane(contentPane);
        contentPane.setLayout(null);

        JLabel lblTipoDocumento = new JLabel("Tipo Documento");
        lblTipoDocumento.setBounds(10, 11, 101, 14);
        contentPane.add(lblTipoDocumento);

        textField = new JTextField();
        textField.setBounds(121, 8, 149, 20);
        contentPane.add(textField);
        textField.setColumns(10);

        JLabel lblJCadastrados = new JLabel("J\u00E1 Cadastrados");
        lblJCadastrados.setBounds(10, 72, 94, 14);
        contentPane.add(lblJCadastrados);

        JPanel panel = new JPanel();
        panel.setBounds(10, 92, 414, 158);
        contentPane.add(panel);
        panel.setLayout(null);

        table = new JTable();
        table.setModel(new DefaultTableModel(
            new Object[][] {},
            new String[] {
                "ID Documento", "Descri\u00E7\u00E3o"
            }
        ));
        table.setBounds(10, 141, 394, -129);
        panel.add(table);

        JButton btnCadastrar = new JButton("Cadastrar");
        btnCadastrar.setBounds(10, 38, 105, 23);
        contentPane.add(btnCadastrar);

        JButton btnAtualizar = new JButton("Atualizar");
        btnAtualizar.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {

                documentoDAO u = new documentoDAO();
                String[] colunas = { "idTipoDoc", "Tipo"};
                DefaultTableModel dados = new DefaultTableModel(colunas, 2);
                List<documento> documentos = u.SelectFull();

                for (documento documento : documentos) {
                    dados.addRow(new String[] { "" + documento.getIdTipoDoc(), documento.getTipo()});
                }

                table.setModel(dados);

            }
        });
        btnAtualizar.setBounds(163, 39, 101, 23);
        contentPane.add(btnAtualizar);
    }
}

  

document

package Model;

public class documento {

    private  int idTipoDoc;
    private  String Tipo;

    public  int getIdTipoDoc() {
        return idTipoDoc;
    }

    public void setIdTipoDoc(int idTipoDoc) {
        this.idTipoDoc = idTipoDoc;
    }

    public  String getTipo() {
        return Tipo;
    }

    public void setTipo(String tipo) {
        Tipo = tipo;
    }

    public void add(documento doc) {
        // TODO Auto-generated method stub

    }

}

  

documentDAO

package DAO;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import Model.documento;
import Model.Usuario;

public class documentoDAO {

    public boolean acesso;
    private Connection con = null;

    public void documentoDAO() {
        this.con = new conexaoDAO().getConexao();
    }



    public void Inserir(documento doc) {
        String sql = "INSERT INTO tipodoc(idTipoDoc, Tipo)VALUES (null,?)";
        try {
            PreparedStatement stmt = con.prepareStatement(sql);
            stmt.setString(1, doc.getTipo());
            stmt.execute();
            stmt.close();
        } catch (SQLException e) {
            throw new RuntimeException(e);
        }
    }

    public List<documento> SelectFull() {
        String sql = "SELECT * FROM tipodoc";
        try {
            List<documento> documentos = new ArrayList<documento>();
            PreparedStatement stmt = con.prepareStatement(sql);
            ResultSet result = stmt.executeQuery();
            while (result.next()) {
                documento doc = new documento();
                doc.setIdTipoDoc(result.getInt("idTipoDoc"));
                doc.setTipo(result.getString("Tipo"));
                doc.add(doc);
            }
            result.close();
            stmt.close();
            return documentos;
        } catch (SQLException e) {
            throw new RuntimeException(e);
        }
    }

}