Função do botão Excluir não funciona

yuseirender · Junho 11, 2019, 6:36am

Estou desenvolvendo um software para o tcc
já criei a conexão com o banco de dados e a função de inserir dados no banco de dados
ao programar o seguinte codigo ao botão excluir, o mesmo não retorna nada e o botão não funciona:

try {
    PreparedStatement pst = conecta.con.prepareStatement("delete from classe where id="+id+"");
} catch (SQLException ex) {
    Logger.getLogger(CriarClasse.class.getName()).log(Level.SEVERE, null, ex);
}

conexaoDB.JAVA:

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package View;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JOptionPane;

public class ConexaoDB {
public Statement stmt;
public ResultSet rs;
private String driver = "com.mysql.jdbc.Driver";
private String host = "jdbc:mysql://localhost:3306/escola";
private String usuario = "root";
private String senha = "";
public Connection con;
  
public void conexao(){
    try {
        System.setProperty("jdbc.Drivers", driver);
        con= DriverManager.getConnection(host, usuario, senha);
        //JOptionPane.showMessageDialog(null, "Conectado com sucesso!");
    } catch (SQLException ex) {
        JOptionPane.showMessageDialog(null, "Erro de conexão!\n Erro: "+ex.getMessage());
    }
}

public void executaSQL(String sql){
    try { 
        stmt = con.createStatement(rs.TYPE_SCROLL_INSENSITIVE, rs.CONCUR_READ_ONLY);
        rs = stmt.executeQuery(sql);
    } catch (SQLException ex) {
        JOptionPane.showMessageDialog(null, "Erro no executaSQL!\n Erro: "+ex.getMessage());
    }
}

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



}

Criar Classe.JAVA

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package View;

import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JOptionPane;
import javax.swing.table.DefaultTableModel;

/**
 *
 * @author marco
 */
public class CriarClasse extends javax.swing.JFrame {

    ConexaoDB conecta = new ConexaoDB();
    /**
     * Creates new form CriarClasse
     */
    public CriarClasse() {
        initComponents();
        conecta.conexao();
    }

    /**
     * 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() {

        jPanel1 = new javax.swing.JPanel();
        lbltitulo = new javax.swing.JLabel();
        lblclasse = new javax.swing.JLabel();
        campoclasse = new javax.swing.JTextField();
        lblsetor = new javax.swing.JLabel();
        camposetor = new javax.swing.JTextField();
        btncriar = new javax.swing.JButton();
        btnatualizar = new javax.swing.JButton();
        btndeletar = new javax.swing.JButton();
        btnfechar = new javax.swing.JButton();
        jScrollPane2 = new javax.swing.JScrollPane();
        tabela1 = new javax.swing.JTable();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        jPanel1.setBackground(new java.awt.Color(0, 153, 153));

        lbltitulo.setFont(new java.awt.Font("Tahoma", 1, 36)); // NOI18N
        lbltitulo.setForeground(new java.awt.Color(255, 255, 255));
        lbltitulo.setText("Criar Classe");

        lblclasse.setFont(new java.awt.Font("Tahoma", 1, 11)); // NOI18N
        lblclasse.setForeground(new java.awt.Color(255, 255, 255));
        lblclasse.setText("Nome da classe:");

        lblsetor.setFont(new java.awt.Font("Tahoma", 1, 11)); // NOI18N
        lblsetor.setForeground(new java.awt.Color(255, 255, 255));
        lblsetor.setText("Setor:");

        btncriar.setFont(new java.awt.Font("Tahoma", 1, 11)); // NOI18N
        btncriar.setText("Criar");
        btncriar.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                btncriarActionPerformed(evt);
            }
        });

        btnatualizar.setFont(new java.awt.Font("Tahoma", 1, 11)); // NOI18N
        btnatualizar.setText("Atualizar");
        btnatualizar.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                btnatualizarActionPerformed(evt);
            }
        });

        btndeletar.setFont(new java.awt.Font("Tahoma", 1, 11)); // NOI18N
        btndeletar.setText("Deletar");
        btndeletar.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                btndeletarActionPerformed(evt);
            }
        });

        btnfechar.setFont(new java.awt.Font("Tahoma", 1, 11)); // NOI18N
        btnfechar.setText("Fechar");
        btnfechar.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                btnfecharActionPerformed(evt);
            }
        });

        tabela1.setModel(new javax.swing.table.DefaultTableModel(
            new Object [][] {

            },
            new String [] {
                "ID", "CLASSE", "SETOR"
            }
        ));
        tabela1.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseClicked(java.awt.event.MouseEvent evt) {
                tabela1MouseClicked(evt);
            }
        });
        jScrollPane2.setViewportView(tabela1);

        javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
        jPanel1.setLayout(jPanel1Layout);
        jPanel1Layout.setHorizontalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel1Layout.createSequentialGroup()
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(jPanel1Layout.createSequentialGroup()
                        .addGap(98, 98, 98)
                        .addComponent(lbltitulo))
                    .addGroup(jPanel1Layout.createSequentialGroup()
                        .addGap(61, 61, 61)
                        .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                            .addComponent(lblsetor)
                            .addComponent(lblclasse))
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                                .addComponent(campoclasse)
                                .addComponent(camposetor, javax.swing.GroupLayout.DEFAULT_SIZE, 200, Short.MAX_VALUE))
                            .addGroup(jPanel1Layout.createSequentialGroup()
                                .addGap(10, 10, 10)
                                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                                    .addComponent(btndeletar, javax.swing.GroupLayout.DEFAULT_SIZE, 83, Short.MAX_VALUE)
                                    .addComponent(btncriar, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
                                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                                    .addComponent(btnatualizar, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                                    .addComponent(btnfechar, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)))))
                    .addGroup(jPanel1Layout.createSequentialGroup()
                        .addContainerGap()
                        .addComponent(jScrollPane2, javax.swing.GroupLayout.PREFERRED_SIZE, 415, javax.swing.GroupLayout.PREFERRED_SIZE)))
                .addContainerGap(15, Short.MAX_VALUE))
        );
        jPanel1Layout.setVerticalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel1Layout.createSequentialGroup()
                .addComponent(lbltitulo)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(lblclasse)
                    .addComponent(campoclasse, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(lblsetor)
                    .addComponent(camposetor, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(btnatualizar, javax.swing.GroupLayout.PREFERRED_SIZE, 23, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(btncriar, javax.swing.GroupLayout.PREFERRED_SIZE, 23, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(btndeletar)
                    .addComponent(btnfechar))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                .addComponent(jScrollPane2, javax.swing.GroupLayout.PREFERRED_SIZE, 402, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addGap(11, 11, 11))
        );

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
        );

        pack();
    }// </editor-fold>                        

    private void tabela1MouseClicked(java.awt.event.MouseEvent evt) {                                     
        // TODO add your handling code here:
        int indexrow= tabela1.getSelectedRow();
        
        DefaultTableModel model = (DefaultTableModel)tabela1.getModel();
        id=model.getValueAt(indexrow, 0).toString();
        campoclasse.setText(model.getValueAt(indexrow, 1).toString());
        camposetor.setText(model.getValueAt(indexrow, 2).toString());        
    }                                    

    private void btncriarActionPerformed(java.awt.event.ActionEvent evt) {                                         
        try {
            // TODO add your handling code here:
            PreparedStatement pst= conecta.con.prepareStatement("insert into classe (classe,setor) values(?,?) ");
            pst.setString(1, campoclasse.getText());
            pst.setString(2, camposetor.getText());
            pst.executeUpdate();
            JOptionPane.showMessageDialog(rootPane, "Criado com sucesso!");
        } catch (SQLException ex) {
            JOptionPane.showMessageDialog(rootPane, "Erro na inserção!\n Erro: "+ex);
        }
    }                                        
String id;
    private void btnatualizarActionPerformed(java.awt.event.ActionEvent evt) {                                             
        // TODO add your handling code here:
    }                                            

    private void btndeletarActionPerformed(java.awt.event.ActionEvent evt) {                                           
        try {
            PreparedStatement pst = conecta.con.prepareStatement("delete from classe where id="+id+"");
        } catch (SQLException ex) {
            Logger.getLogger(CriarClasse.class.getName()).log(Level.SEVERE, null, ex);
        }
        
    }                                          

    private void btnfecharActionPerformed(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(CriarClasse.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(CriarClasse.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(CriarClasse.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(CriarClasse.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>

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

    // Variables declaration - do not modify                     
    private javax.swing.JButton btnatualizar;
    private javax.swing.JButton btncriar;
    private javax.swing.JButton btndeletar;
    private javax.swing.JButton btnfechar;
    private javax.swing.JTextField campoclasse;
    private javax.swing.JTextField camposetor;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JScrollPane jScrollPane2;
    private javax.swing.JLabel lblclasse;
    private javax.swing.JLabel lblsetor;
    private javax.swing.JLabel lbltitulo;
    private javax.swing.JTable tabela1;
    // End of variables declaration                   
}

CONEXAODB:
conexao

CRIAR CLASSE.JAVA
form%20criar%20classe

staroski · Junho 11, 2019, 10:19am

yuseirender:

o seguinte codigo ao botão excluir, o mesmo não retorna nada e o botão não funciona:

try {
    PreparedStatement pst = conecta.con.prepareStatement("delete from classe where id="+id+"");
} catch (SQLException ex) {
    Logger.getLogger(CriarClasse.class.getName()).log(Level.SEVERE, null, ex);
}

É que esse código só instancia o PreparedStatement (do jeito errado) e não o executa.

try {
            PreparedStatement pst = conecta.con.prepareStatement("delete from classe where id=?"); // Não concatene parâmetros na query
            pst.setString(1, id); // sete os parâmetros com os métodos do PreparedStatement
            pst.executeUpdate(); // execute ele
        } catch (SQLException ex) {
            Logger.getLogger(CriarClasse.class.getName()).log(Level.SEVERE, null, ex);
        }

yuseirender · Junho 11, 2019, 5:46pm

Fiz desta maneira, está funcionando mas não sei se pode acarretar algum problema de memoria:

    if(id!=null)
    {

        try{
            PreparedStatement pst= conecta.con.prepareStatement("delete from classe where id="+id+" ");
            Statement stmt= conecta.con.createStatement();
            pst.execute();
            JOptionPane.showMessageDialog(null, "Deletado!");
            getdata();
            vazio();

        }
        catch(Exception e)
        {
            JOptionPane.showMessageDialog(null, "Error!"+e);
        }
    }
    else
    {
        JOptionPane.showMessageDialog(null, "Selecione um item para deletar!");
    }

staroski · Junho 12, 2019, 12:56pm

yuseirender:

Fiz desta maneira, está funcionando mas não sei se pode acarretar algum problema de memoria:

    if(id!=null)
    {

        try{
            PreparedStatement pst= conecta.con.prepareStatement("delete from classe where id="+id+" ");
            Statement stmt= conecta.con.createStatement();
            pst.execute();
            JOptionPane.showMessageDialog(null, "Deletado!");
            getdata();
            vazio();

        }
        catch(Exception e)
        {
            JOptionPane.showMessageDialog(null, "Error!"+e);
        }
    }
    else
    {
        JOptionPane.showMessageDialog(null, "Selecione um item para deletar!");
    }

Problema de memória não, mas você está usando o PreparedStatement como se fosse apenas um Statement.
O PreparedStatement serve justamente para você passar parâmetros para o banco sem concatenar eles na query SQL.
Dessa forma:

if (id != null) {
    try {
        PreparedStatement pst= conecta.con.prepareStatement("delete from classe where id=?"); // o ? indica um parâmetro
        pst.setString(1, id); // aqui eu seto o 1º (e único) parâmetro
        pst.executeUpdate(); // agora executo o PreparedStatement
        JOptionPane.showMessageDialog(null, "Deletado!"); // está certo apresentar telas no código que acessa o banco?
        getdata(); // pra que isso?
        vazio();   // pra que isso?
    } catch(Exception e) {
        JOptionPane.showMessageDialog(null, "Error! " + e); // está certo apresentar telas no código que acessa o banco?
    }
} else {
    JOptionPane.showMessageDialog(null, "Selecione um item para deletar!"); // está certo apresentar telas no código que acessa o banco?
}

Função do botão Excluir não funciona

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