Error entering database data into Jtable

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I’m having a problem loading the data into a Jtable, use BD Derby, the database connection works more when trying to open the Jframe Cad_usuarios appears the error below:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at Controle.ConexaoBD.executaSQL(ConexaoBD.java:57)
at Visao.Cad_Usuarios.preencherTabela(Cad_Usuarios.java:235)
at Visao.Cad_Usuarios.<init>(Cad_Usuarios.java:32)
at Visao.cadastro.jMUsuariosActionPerformed(cadastro.java:147)
at Visao.cadastro.access$300(cadastro.java:9)
at Visao.cadastro$4.actionPerformed(cadastro.java:96)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.AbstractButton.doClick(AbstractButton.java:376)
at javax.swing.plaf.basic.BasicMenuItemUI.doClick(BasicMenuItemUI.java:833)
at javax.swing.plaf.basic.BasicMenuItemUI$Handler.mouseReleased(BasicMenuItemUI.java:877)
at java.awt.Component.processMouseEvent(Component.java:6533)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
at java.awt.Component.processEvent(Component.java:6298)
at java.awt.Container.processEvent(Container.java:2236)
at java.awt.Component.dispatchEventImpl(Component.java:4889)
at java.awt.Container.dispatchEventImpl(Container.java:2294)
at java.awt.Component.dispatchEvent(Component.java:4711)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4888)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4525)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4466)
at java.awt.Container.dispatchEventImpl(Container.java:2280)
at java.awt.Window.dispatchEventImpl(Window.java:2746)
at java.awt.Component.dispatchEvent(Component.java:4711)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
at java.awt.EventQueue.access$500(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:709)
at java.awt.EventQueue$3.run(EventQueue.java:703)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:90)
at java.awt.EventQueue$4.run(EventQueue.java:731)
at java.awt.EventQueue$4.run(EventQueue.java:729)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

User class:

package Modelo;

import java.io.Serializable;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;


@Entity
@Table(name="ROOT.USUARIO")
public class Usuario implements Serializable{


    @Id
    @Column(name = "LOGIN", nullable = false)
    private String login;

    @Column(name = "SENHA", nullable = false)
    private String senha;


    @Column(name = "NOME", nullable = false)
    private String nome;

    public String getLogin() {
        return login;
    }

    public void setLogin(String login) {
        this.login = login;
    }

    public String getSenha() {
        return senha;
    }

    public void setSenha(String senha) {
        this.senha = senha;
    }

    public String getNome() {
        return nome;
    }

    public void setNome(String nome) {
        this.nome = nome;
    }

     public Usuario(){}

}

Form Cad_usuarios

package Visao;

import Controle.ConexaoBD;
import Modelo.ModeloTabela;
import Modelo.Usuario;
import java.sql.SQLException;
import java.util.ArrayList;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.swing.JOptionPane;
import javax.swing.ListSelectionModel;
import static org.eclipse.persistence.jpa.jpql.parser.Expression.SQL;


public class Cad_Usuarios extends javax.swing.JFrame {
    EntityManagerFactory factory;
    EntityManager manager;

    ConexaoBD conecta = new ConexaoBD();

    public Cad_Usuarios() {
        initComponents();
        preencherTabela("select * from usuarios order by login");
        try{
            factory = Persistence.createEntityManagerFactory("Ponto_DablioPU");
            manager = factory.createEntityManager();
        }catch(Exception e){
            System.exit(1);
        }
    }

    public void limpar(){
        jTLogin.setText(null);
        jTNome.setText(null);
        jPFSenha.setText(null);    
    }
    private void jBSalvarActionPerformed(java.awt.event.ActionEvent evt) {                                         

        Usuario user = new Usuario();

        user.setLogin(jTLogin.getText());

        user.setNome(jTNome.getText());

        user.setSenha(jPFSenha.getText());

        manager.getTransaction().begin();

        manager.persist(user);

        manager.getTransaction().commit();

        JOptionPane.showMessageDialog(null, "Usuário Cadastrado com Sucesso!");

        limpar();

    }                                        

    private void jBSairActionPerformed(java.awt.event.ActionEvent evt) {                                       
        dispose();
    }                                      

    private void jBLimparActionPerformed(java.awt.event.ActionEvent evt) {                                         
        limpar();
    }                                        

    public void preencherTabela(String SQL){
        ArrayList dados = new ArrayList();

        String[] Colunas = new String[]{"Login","Senha","Nome"};


        conecta.executaSQL(SQL);
        try{
            conecta.rs.first();
            do{
                dados.add(new Object[]{conecta.rs.getInt("login"),conecta.rs.getString("senha"),conecta.rs.getString("nome")});
            }while(conecta.rs.next());
        }catch (SQLException ex){
            JOptionPane.showMessageDialog(null,"Erro ao preencher o ArrayList! \n ERRO:");
        }

        ModeloTabela modelo = new ModeloTabela(dados, Colunas);
        jTable1.setModel(modelo);
        jTable1.getColumnModel().getColumn(0).setPreferredWidth(150);
        jTable1.getColumnModel().getColumn(0).setResizable(false);

        jTable1.getColumnModel().getColumn(1).setPreferredWidth(150);
        jTable1.getColumnModel().getColumn(1).setResizable(false);

        jTable1.getColumnModel().getColumn(2).setPreferredWidth(80);
        jTable1.getColumnModel().getColumn(2).setResizable(false);

        jTable1.getTableHeader().setReorderingAllowed(false);
        jTable1.setAutoResizeMode(jTable1.AUTO_RESIZE_OFF);

        jTable1.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);

    }

Modelotabela class

package Modelo;

import java.util.ArrayList;
import javax.swing.table.AbstractTableModel;

public class ModeloTabela extends AbstractTableModel{
private ArrayList linhas = null;
private String[] colunas = null;


public ModeloTabela(ArrayList lin,String[] col){
    setLinhas(lin);
    setColunas(col);

}

public ArrayList getLinhas(){
    return linhas;
}

public void setLinhas(ArrayList dados){
    linhas = dados;
}

public String []  getColunas(){
    return colunas;
}

public void setColunas(String[] nomes){
    colunas = nomes;
}

public int getColumnCount(){
    return colunas.length;
}

public int getRowCount(){
    return linhas.size();
}

public String getColumnName(int numCol){
    return colunas[numCol];
}

public Object getValueAt(int numLin, int numCol){
    Object[] linha = (Object[])getLinhas().get(numLin);
    return linha[numCol];
}
}

Conexaobd Class

import java.sql.*;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JOptionPane;

public class ConexaoBD {


public Statement stm;
public ResultSet rs;
private String driver = "org.apache.derby.jdbc.EmbeddedDriver";
private String caminho = "jdbc:derby://localhost:1527/ponto_dablio";
private String usuario = "root";
private String senha = "root";
public Connection connection;

public void conexao(){

    try {
        System.setProperty("jdbc.Drivers", driver);
        connection = DriverManager.getConnection(caminho, usuario, senha);
    } catch (SQLException ex) {
        JOptionPane.showMessageDialog(null,"CONECTADO COM SUCESSO!!\n Erro:" + ex.getMessage());
    }

}

public void executaSQL(String sql) { 

   try {
       stm =     connection.createStatement(rs.TYPE_SCROLL_INSENSITIVE,rs.CONCUR_READ_ONLY);
       rs = stm.executeQuery(sql);
       } catch (SQLException ex) {
         JOptionPane.showMessageDialog(null,"ERRO DE EXECUTASQL!!\n ERRO: " + ex.getMessage());
       }
}

public void desconecta(){
    try{
        connection.close();
    }catch (SQLException ex){
        JOptionPane.showMessageDialog(null,"Erro ao fechar conexão!\n Erro:"         + ex.getMessage());
    }
}


}

I made the change but keeps giving error says that the table "users" does not exist, error: 

`Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at Visao.Cad_Usuarios.preencherTabela(Cad_Usuarios.java:238)
at Visao.Cad_Usuarios.<init>(Cad_Usuarios.java:32)
at Visao.cadastro.jMUsuariosActionPerformed(cadastro.java:147)
at Visao.cadastro.access$300(cadastro.java:9)
at Visao.cadastro$4.actionPerformed(cadastro.java:96)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.AbstractButton.doClick(AbstractButton.java:376)
at javax.swing.plaf.basic.BasicMenuItemUI.doClick(BasicMenuItemUI.java:833)
at javax.swing.plaf.basic.BasicMenuItemUI$Handler.mouseReleased(BasicMenuItemUI.java:877)
at java.awt.Component.processMouseEvent(Component.java:6533)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
at java.awt.Component.processEvent(Component.java:6298)
at java.awt.Container.processEvent(Container.java:2236)
at java.awt.Component.dispatchEventImpl(Component.java:4889)
at java.awt.Container.dispatchEventImpl(Container.java:2294)
at java.awt.Component.dispatchEvent(Component.java:4711)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4888)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4525)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4466)
at java.awt.Container.dispatchEventImpl(Container.java:2280)
at java.awt.Window.dispatchEventImpl(Window.java:2746)
at java.awt.Component.dispatchEvent(Component.java:4711)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
at java.awt.EventQueue.access$500(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:709)
at java.awt.EventQueue$3.run(EventQueue.java:703)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:90)
at java.awt.EventQueue$4.run(EventQueue.java:731)
at java.awt.EventQueue$4.run(EventQueue.java:729)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)
java nullpointerexception connection

  • I made the change further continued giving error, I wrote the error below, thank you

  • sorry, I’m new, I added above the error presented after making the informed change.

1 answer

1


You did not start the connection in the method preencheTabela(). Failed to invoke the method conexao() class ConexaoBD:

public void preencherTabela(String SQL){
    ArrayList dados = new ArrayList();

    String[] Colunas = new String[]{"Login","Senha","Nome"};

    conecta.conexao();

    conecta.executaSQL(SQL);
    try{
        conecta.rs.first();
        do{
            dados.add(new Object[]{conecta.rs.getInt("login"),conecta.rs.getString("senha"),conecta.rs.getString("nome")});
        }while(conecta.rs.next());
    }catch (SQLException ex){
        JOptionPane.showMessageDialog(null,"Erro ao preencher o ArrayList! \n ERRO:");
    }

...

As for the second error, observing your model, the table is called "USER" and in the query that populates the table you are passing as "users". Fix the table name in the query:

public Cad_Usuarios() {
    initComponents();
    preencherTabela("select * from usuario order by login");
    try{
        factory = Persistence.createEntityManagerFactory("Ponto_DablioPU");
        manager = factory.createEntityManager();
    }catch(Exception e){
        System.exit(1);
    }
}

Recommended reading: How Try-with-Resources works?

  • I solved the mistake for now, tomorrow I will continue in the project and if the error appears again I report, thank you even Articuno. There was a String in the bank that was like . getInt to add in the bank and the table name was wrong anyway, thanks!!

  • @Dhouglassilvagomes if the answer has helped to resolve the question, see here how to conclude the question.

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