Erro Java - java.lang.nullpointerexception: cannot invoke "java.sql.connection.preparestatement(string)" because "this.conector" is null

Lucas9 · Dezembro 2, 2023, 10:32pm

Ao rodar meu projeto, ao tentar acessar minha tela Principal em outros computadores, apresenta o erro java.lang.nullpointerexception: cannot invoke “java.sql.connection.preparestatement(string)” because “this.conector” is null.

public class moduloConexao {

public static Connection conector(){
    Connection conector = null;
    
    String URL = "jdbc:mysql://localhost:3306/db_biblioteca";
    String USER = "root";
    String PASSWORD = "root";
    
    try{
    conector = DriverManager.getConnection(URL, USER, PASSWORD);
    return conector;
    } catch(SQLException e) {
        e.printStackTrace();
        return null;
    } 
}

}

Tela Principal

public class TelaPrincipal extends javax.swing.JFrame {

Connection conector = null;

/**
 * Creates new form TelaPrincipal
 */
public TelaPrincipal() {
    initComponents();
    conector = moduloConexao.conector();
}

/**
 * This method is called from within the constructor to initialize the form.
 * WARNING: Do NOT modify this code. The content of this method is always
 * regenerated by the Form Editor.
 */
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">                          
private void initComponents() {

    Desktop = new javax.swing.JDesktopPane();
    lblUsuario = new javax.swing.JLabel();
    lblData = new javax.swing.JLabel();
    jLabel1 = new javax.swing.JLabel();
    Menu = new javax.swing.JMenuBar();
    menCad = new javax.swing.JMenu();
    menCadCli = new javax.swing.JMenuItem();
    menCadOs = new javax.swing.JMenuItem();
    menCadUsu = new javax.swing.JMenuItem();
    MenRel = new javax.swing.JMenu();
    menRelCli = new javax.swing.JMenuItem();
    menRelSer = new javax.swing.JMenuItem();
    MenAju = new javax.swing.JMenu();
    menAjuSob = new javax.swing.JMenuItem();
    MenOpc = new javax.swing.JMenu();
    menOpcSai = new javax.swing.JMenuItem();

    setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
    setTitle("X - Sistema para Controle de OS");
    setPreferredSize(new java.awt.Dimension(915, 523));
    setResizable(false);
    addWindowListener(new java.awt.event.WindowAdapter() {
        public void windowActivated(java.awt.event.WindowEvent evt) {
            formWindowActivated(evt);
        }
    });

    javax.swing.GroupLayout DesktopLayout = new javax.swing.GroupLayout(Desktop);
    Desktop.setLayout(DesktopLayout);
    DesktopLayout.setHorizontalGroup(
        DesktopLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 641, Short.MAX_VALUE)
    );
    DesktopLayout.setVerticalGroup(
        DesktopLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 481, Short.MAX_VALUE)
    );

    lblUsuario.setFont(new java.awt.Font("Tahoma", 1, 18)); // NOI18N
    lblUsuario.setText("Usuário");

    lblData.setFont(new java.awt.Font("Tahoma", 1, 24)); // NOI18N
    lblData.setText("Data");

    menCad.setText("Cadastro");

    menCadCli.setAccelerator(javax.swing.KeyStroke.getKeyStroke(java.awt.event.KeyEvent.VK_C, java.awt.event.InputEvent.ALT_DOWN_MASK));
    menCadCli.setText("Cliente");
    menCadCli.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            menCadCliActionPerformed(evt);
        }
    });
    menCad.add(menCadCli);

    menCadOs.setAccelerator(javax.swing.KeyStroke.getKeyStroke(java.awt.event.KeyEvent.VK_O, java.awt.event.InputEvent.ALT_DOWN_MASK));
    menCadOs.setText("Os");
    menCadOs.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            menCadOsActionPerformed(evt);
        }
    });
    menCad.add(menCadOs);

    menCadUsu.setAccelerator(javax.swing.KeyStroke.getKeyStroke(java.awt.event.KeyEvent.VK_U, java.awt.event.InputEvent.ALT_DOWN_MASK));
    menCadUsu.setText("Usuarios");
    menCadUsu.setEnabled(false);
    menCadUsu.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            menCadUsuActionPerformed(evt);
        }
    });
    menCad.add(menCadUsu);

    Menu.add(menCad);

    MenRel.setText("Relatório");
    MenRel.setEnabled(false);

    menRelCli.setAccelerator(javax.swing.KeyStroke.getKeyStroke(java.awt.event.KeyEvent.VK_R, java.awt.event.InputEvent.ALT_DOWN_MASK));
    menRelCli.setText("Clientes");
    menRelCli.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            menRelCliActionPerformed(evt);
        }
    });
    MenRel.add(menRelCli);

    menRelSer.setAccelerator(javax.swing.KeyStroke.getKeyStroke(java.awt.event.KeyEvent.VK_S, java.awt.event.InputEvent.ALT_DOWN_MASK));
    menRelSer.setText("Serviços");
    menRelSer.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            menRelSerActionPerformed(evt);
        }
    });
    MenRel.add(menRelSer);

    Menu.add(MenRel);

    MenAju.setText("Ajuda");

    menAjuSob.setAccelerator(javax.swing.KeyStroke.getKeyStroke(java.awt.event.KeyEvent.VK_F1, java.awt.event.InputEvent.ALT_DOWN_MASK));
    menAjuSob.setText("Sobre");
    menAjuSob.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            menAjuSobActionPerformed(evt);
        }
    });
    MenAju.add(menAjuSob);

    Menu.add(MenAju);

    MenOpc.setText("Opções");

    menOpcSai.setAccelerator(javax.swing.KeyStroke.getKeyStroke(java.awt.event.KeyEvent.VK_F4, java.awt.event.InputEvent.ALT_DOWN_MASK));
    menOpcSai.setText("Sair");
    menOpcSai.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            menOpcSaiActionPerformed(evt);
        }
    });
    MenOpc.add(menOpcSai);

    Menu.add(MenOpc);

    setJMenuBar(Menu);

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
    getContentPane().setLayout(layout);
    layout.setHorizontalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addContainerGap()
            .addComponent(Desktop, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGroup(layout.createSequentialGroup()
                    .addGap(254, 254, 254)
                    .addComponent(jLabel1))
                .addGroup(layout.createSequentialGroup()
                    .addGap(33, 33, 33)
                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                        .addComponent(lblData)
                        .addComponent(lblUsuario, javax.swing.GroupLayout.PREFERRED_SIZE, 200, javax.swing.GroupLayout.PREFERRED_SIZE))))
            .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGroup(layout.createSequentialGroup()
                    .addGap(16, 16, 16)
                    .addComponent(lblUsuario)
                    .addGap(27, 27, 27)
                    .addComponent(lblData)
                    .addGap(355, 355, 355)
                    .addComponent(jLabel1))
                .addGroup(layout.createSequentialGroup()
                    .addContainerGap()
                    .addComponent(Desktop, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)))
            .addContainerGap(30, Short.MAX_VALUE))
    );

    setSize(new java.awt.Dimension(915, 548));
    setLocationRelativeTo(null);
}// </editor-fold>                        

private void menRelSerActionPerformed(java.awt.event.ActionEvent evt) {                                          
    // TODO add your handling code here:
}                                         

private void menOpcSaiActionPerformed(java.awt.event.ActionEvent evt) {                                          
    // TODO add your handling code here:
    int sair = JOptionPane.showConfirmDialog(null, "tem certeze que deseja sair?", "Atenção", JOptionPane.YES_NO_OPTION);
    if (sair == JOptionPane.YES_OPTION) {
        System.exit(0);
    }
}                                         

private void formWindowActivated(java.awt.event.WindowEvent evt) {                                     
    // TODO add your handling code here:
    Date data = new Date();
    DateFormat formatador = DateFormat.getDateInstance(DateFormat.SHORT);
    lblData.setText(formatador.format(data));
}                                    

private void menAjuSobActionPerformed(java.awt.event.ActionEvent evt) {                                          
    // TODO add your handling code here:

    TelaSobre sobre = new TelaSobre();
    sobre.setVisible(true);
}                                         

private void menCadUsuActionPerformed(java.awt.event.ActionEvent evt) {                                          
    // TODO add your handling code here:
    TelaUsuario usuario = new TelaUsuario();
    usuario.setVisible(true);
    Desktop.add(usuario);
}                                         

private void menCadCliActionPerformed(java.awt.event.ActionEvent evt) {                                          
    // TODO add your handling code here:
    TelaCliente cliente = new TelaCliente();
    cliente.setVisible(true);
    Desktop.add(cliente);
}                                         

private void menCadOsActionPerformed(java.awt.event.ActionEvent evt) {                                         
    // TODO add your handling code here:
    TelaOS os = new TelaOS();
    os.setVisible(true);
    Desktop.add(os);
}                                        

private void menRelCliActionPerformed(java.awt.event.ActionEvent evt) {                                          
    // TODO add your handling code here:

    
}                                         

/**
 * @param args the command line arguments
 */
public static void main(String args[]) {
    /* Set the Nimbus look and feel */
    //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
    /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
     * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
     */
    try {
        for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
            if ("Nimbus".equals(info.getName())) {
                javax.swing.UIManager.setLookAndFeel(info.getClassName());
                break;
            }
        }
    } catch (ClassNotFoundException ex) {
        java.util.logging.Logger.getLogger(TelaPrincipal.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (InstantiationException ex) {
        java.util.logging.Logger.getLogger(TelaPrincipal.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (IllegalAccessException ex) {
        java.util.logging.Logger.getLogger(TelaPrincipal.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (javax.swing.UnsupportedLookAndFeelException ex) {
        java.util.logging.Logger.getLogger(TelaPrincipal.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    }
    //</editor-fold>
    //</editor-fold>
    //</editor-fold>
    //</editor-fold>

    /* Create and display the form */
    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            new TelaPrincipal().setVisible(true);
        }
    });
}

// Variables declaration - do not modify                     
private javax.swing.JDesktopPane Desktop;
private javax.swing.JMenu MenAju;
private javax.swing.JMenu MenOpc;
public static javax.swing.JMenu MenRel;
private javax.swing.JMenuBar Menu;
private javax.swing.JLabel jLabel1;
private javax.swing.JLabel lblData;
public static javax.swing.JLabel lblUsuario;
private javax.swing.JMenuItem menAjuSob;
private javax.swing.JMenu menCad;
private javax.swing.JMenuItem menCadCli;
private javax.swing.JMenuItem menCadOs;
public static javax.swing.JMenuItem menCadUsu;
private javax.swing.JMenuItem menOpcSai;
private javax.swing.JMenuItem menRelCli;
private javax.swing.JMenuItem menRelSer;

staroski · Dezembro 4, 2023, 8:39am

Cadê a classe onde você chama o prepareStatement ?

Lucas9 · Dezembro 4, 2023, 10:54am

public class TelaCliente extends javax.swing.JInternalFrame {

Connection conector = null;
PreparedStatement pst = null;
ResultSet rs = null;

/**
 * Creates new form TelaCliente
 */
public TelaCliente() {
    initComponents();
    conector = moduloConexao.conector();
}

private void adicionar() {
    String sql = "INSERT INTO clientes (nomeclie, endereço, foneCli, emailCli, cpfCli) VALUES(?, ?, ?, ?, ?)";
    try {
        pst = conector.prepareStatement(sql);
        pst.setString(1, txtCliNome.getText());
        pst.setString(2, txtCliEndereco.getText());
        pst.setString(3, txtCliFone.getText());
        pst.setString(4, txtCliEmail.getText());
        pst.setString(5, txtCliCpf.getText());

        if ((txtCliNome.getText().isEmpty()) || (txtCliFone.getText().isEmpty()) || (txtCliCpf.getText().isEmpty())) {
            JOptionPane.showMessageDialog(null, "Preencha todos os campos obrigatórios!");
        } else {
            int adicionado = pst.executeUpdate();
            if (adicionado > 0) {
                JOptionPane.showMessageDialog(null, "Adicionado com sucesso!");
                txtCliNome.setText(null);
                txtCliEndereco.setText(null);
                txtCliFone.setText(null);
                txtCliEmail.setText(null);
                txtCliCpf.setText(null);
            }
        }
    } catch (Exception e) {
        JOptionPane.showMessageDialog(null, e);
    }
}

private void pesquisar_cliente() {
    String sql = "SELECT * FROM clientes WHERE Cpfcli=?";
    try {
        pst = conector.prepareStatement(sql);
        pst.setString(1, txtCliCpf.getText());

        rs = pst.executeQuery();
        if (rs.next()) {
            txtCliIdcli.setText(rs.getString(2));
            txtCliNome.setText(rs.getString(3));
            txtCliEndereco.setText(rs.getString(4));
            txtCliFone.setText(rs.getString(5));
            txtCliEmail.setText(rs.getString(6));
        } else {
            JOptionPane.showMessageDialog(null, "Usuário não cadastrado!");
            txtCliNome.setText(null);
            txtCliEndereco.setText(null);
            txtCliFone.setText(null);
            txtCliEmail.setText(null);
        }
    } catch (Exception e) {
        JOptionPane.showMessageDialog(null, e);
    }
    btnAdd.setEnabled(false);
}

private void alterar() {

    String sql = "UPDATE clientes SET idcli=?, nomeclie=?, endereço=?, foneCli=?, emailcli=? WHERE cpfCli=?";
   
    try {
        pst = conector.prepareStatement(sql);
        pst.setString(1, txtCliIdcli.getText());
        pst.setString(2, txtCliNome.getText());
        pst.setString(3, txtCliEndereco.getText());
        pst.setString(4, txtCliFone.getText());
        pst.setString(5, txtCliEmail.getText());
        pst.setString(6, txtCliCpf.getText());
        
        
        if ((txtCliCpf.getText().isEmpty()) || (txtCliNome.getText().isEmpty()) || (txtCliFone.getText().isEmpty())) {
            JOptionPane.showMessageDialog(null, "Preencha todos os campos obrigatórios!");
        } else {
            int adicionado = pst.executeUpdate();
            if (adicionado > 0) {
                JOptionPane.showMessageDialog(null, "Dados do cliente alterados com sucesso!");
                txtCliIdcli.setText(null);
                txtCliNome.setText(null);
                txtCliEndereco.setText(null);
                txtCliFone.setText(null);
                txtCliEmail.setText(null);
                txtCliCpf.setText(null);
                btnAdd.setEnabled(true);
               
            }
        }
    } catch (Exception e) {
        JOptionPane.showMessageDialog(null, e);
    }
}

private void remover() {
int confirm = JOptionPane.showConfirmDialog(null, “Tem certeza que deseja remover esse usuário?”, “Atenção”, JOptionPane.YES_NO_OPTION);
if (confirm == JOptionPane.YES_OPTION) {
String sql = “DELETE FROM clientes WHERE cpfCli=?”;
try {
pst = conector.prepareStatement(sql);
pst.setString(1, txtCliCpf.getText());
int apagado = pst.executeUpdate();
if (apagado > 0) {
JOptionPane.showMessageDialog(null, “Usuário removido com sucesso!”);

                txtCliCpf.setText(null);
                txtCliIdcli.setText(null);
                txtCliNome.setText(null);
                txtCliEndereco.setText(null);
                txtCliFone.setText(null);
                txtCliEmail.setText(null);
                btnAdd.setEnabled(true);
            }
        } catch (Exception e) {
            JOptionPane.showMessageDialog(null, e);
        }
    }

}

staroski · Dezembro 7, 2023, 1:41pm

Posta o StackTrace completo pra gente ver onde que a exceção está ocorrendo.

ViniGodoy · Dezembro 12, 2023, 7:09pm

Esse try catch deve estar mascarando o erro real (que é o de não conseguir criar a conexão). O erro deve estar sendo exibido no seu console, mas vc está ignorando.

Mude ele para:

try{
    conector = DriverManager.getConnection(URL, USER, PASSWORD);
    return conector;
    } catch(SQLException e) {
        throw RuntimeException("Problema ao criar o banco", e);
    }

E aí veja na “cause” da exception o que é.

Erro Java - java.lang.nullpointerexception: cannot invoke "java.sql.connection.preparestatement(string)" because "this.conector" is null

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