Atualizar através da Jtable

try {
            Cliente pessoa = new Cliente();
            ClienteDao pd = new ClienteDao();
            pessoa.setCodigo(30);
            pessoa.setNome("Marco Aurelio Antunes ");
            pessoa.setCidade("Franco da Rocha");
            pessoa.setSexo("M");
            pd.Atualizar(pessoa);
            System.out.println("Atualizado com sucesso!!!");
            PreencherTabela();
        } catch (Exception e) {
            System.out.println("Erro:" + e.getMessage());
        }

public void Atualizar(Cliente p) throws Exception {

        abrirBanco();
        pstmt = con.prepareStatement("UPDATE clientes set cli_nome = ?, cli_cidade = ?, cli_sexo = ? where cli_codigo = ?");
        pstmt.setString(1, p.getNome());
        pstmt.setString(2, p.getCidade());
        pstmt.setString(3, p.getSexo());
        pstmt.setInt(4, p.getCodigo());
        pstmt.execute();
        fecharBanco();
    }

13/03/2012 07:53:49 Principal jButton7ActionPerformed
GRAVE: null
java.lang.NullPointerException
	at Principal.jButton7ActionPerformed(Principal.java:275)
	at Principal.access$600(Principal.java:11)
	at Principal$7.actionPerformed(Principal.java:92)
	at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995)
	at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2318)
	at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
	at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
	at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236)
	at java.awt.Component.processMouseEvent(Component.java:6290)
	at javax.swing.JComponent.processMouseEvent(JComponent.java:3267)
	at java.awt.Component.processEvent(Component.java:6055)
	at java.awt.Container.processEvent(Container.java:2039)
	at java.awt.Component.dispatchEventImpl(Component.java:4653)
	at java.awt.Container.dispatchEventImpl(Container.java:2097)
	at java.awt.Component.dispatchEvent(Component.java:4481)
	at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4575)
	at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4236)
	at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4166)
	at java.awt.Container.dispatchEventImpl(Container.java:2083)
	at java.awt.Window.dispatchEventImpl(Window.java:2482)
	at java.awt.Component.dispatchEvent(Component.java:4481)
	at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:648)
	at java.awt.EventQueue.access$000(EventQueue.java:84)
	at java.awt.EventQueue$1.run(EventQueue.java:607)
	at java.awt.EventQueue$1.run(EventQueue.java:605)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
	at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:98)
	at java.awt.EventQueue$2.run(EventQueue.java:621)
	at java.awt.EventQueue$2.run(EventQueue.java:619)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:618)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)

p = dtm.getProduto(row); //na hora que recebe os dados da tabela

ClienteDao pd = new ClienteDao();
        Cliente p = new Cliente(); 
        try {
             if (jTable1.getSelectedRow() >= 0) {
            String descricao = JOptionPane.showInputDialog(null, "Nova Descricao", "Descricao", JOptionPane.INFORMATION_MESSAGE);
            if (descricao != null && !descricao.trim().isEmpty()) {
                int row = jTable1.getSelectedRow();
               
                p = dtm.getProduto(row); // ESTÁ É A LINHA 275
                //crio novo objeto para alteracao
                Cliente pUpdate = new Cliente();
                pUpdate.setCodigo(p.getCodigo());
                pUpdate.setNome(p.getNome());
                pUpdate.setCidade(p.getCidade());
                pUpdate.setSexo(p.getSexo());
                pd.Atualizar(pUpdate);
                dtm.updateRow(pUpdate, row);
            }
        } else {
            JOptionPane.showMessageDialog(null, "Selecione a linha q deseja alterar", "Alterar", JOptionPane.WARNING_MESSAGE);
        }
        } catch (Exception ex) {
            Logger.getLogger(Principal.class.getName()).log(Level.SEVERE, null, ex);
        }

int row = jTable1.getSelectedRow();
                Cliente p = dtm.getProduto(row);

                //crio novo objeto para alteracao
                Cliente pUpdate = new Cliente();

int row = jTable1.getSelectedRow();
                Cliente p = dtm.getCliente(row);

                //crio novo objeto para alteracao
                Cliente pUpdate = new Cliente();