ArrayList NullPointerExcepti on, Estou tentando trazer uma lista de usuários para minha view e está dando NullPointerException

rrodriguessarri · Novembro 25, 2017, 3:01pm

Clase Usuario

/*

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To change this template file, choose Tools | Templates
and open the template in the editor.
*/
package br.com.lojavirtual.modelo;
import java.sql.Statement;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.List;
import java.util.ArrayList;

/**
*

@author rafael
*/

public class UsuarioDao {

    private final String user = "root";
    private final String password = "Tamires90()";
    private final String url="jdbc:mysql://localhost:3306/LojaVirtual";   
    private Connection con;
    private Statement st;
    private PreparedStatement pst;

    List<Usuario> lista = new ArrayList<>();

    public int conectar(){

        try {
            Class.forName("com.mysql.jdbc.Driver");
            con = DriverManager.getConnection(url, user, password);
            st = con.createStatement();
            return 0;
            
        } catch(ClassNotFoundException e){
            System.out.println("Driver de conexão não encontrado "  + e.getMessage());
           return 1;

        } catch(SQLException ex){
            System.out.println("Base de dados não Encontrada " + ex.getMessage());
            return 2;
        }
    }

    public int desconectar(){
        try{
            con.close();
            return 0;
        } catch(SQLException ex){
            System.out.println("Falha ao desconectar" + ex.getMessage());
            return 1;
        }
    }
    
    

    public int inserir(String nome, String email, String telefone, String login, String senha){
        try{
            st.executeUpdate("INSERT INTO  usuario(nome, email, telefone, login, senha) VALUES ('"+nome+"','"+email+"','"+telefone+"','"+login+"','"+senha+"')");
        return 0;               
        } catch(SQLException e){
            System.out.println(e);
            return 1;
        }

    }
    
    
    

    public List pesquisar(){
        try{
            
            ResultSet rs = st.executeQuery("SELECT * FROM usuario ORDER BY nome");
        while(rs.next()){
            Usuario usuario = new Usuario();
            usuario.setNome(rs.getString("nome"));
            usuario.setEmail(rs.getString("email"));
            usuario.setTelefone(rs.getString("telefone"));
            lista.add(usuario);
        }
        return lista;
        } catch(SQLException ex){
            return lista;
        }

    }

}

rrodriguessarri · Novembro 25, 2017, 3:02pm

Classe UsuarioDao
/*

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 br.com.lojavirtual.modelo;

import java.util.ArrayList;
import java.util.List;

/**
*

@author rafael
*/
public class Usuario {

private long id;
private String nome;
private String email;
private String telefone;
private String login;
private String senha;

public Usuario(){
List Usuario = new ArrayList<>();
}

public long getId(){
return id;
}

public void setId(long id){
this.id = id;
}

public String getNome(){
return nome;
}

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

public String getEmail(){
return email;
}

public void setEmail(String email){
this.email = email;
}

public String getTelegone(){
return telefone;
}

public void setTelefone(String telefone){
this.telefone = telefone;
}

public String getLogin(){
return login;
}

public void setLogin(String login){
if(login.length() < 5){
throw new IllegalArgumentException(“Login tem que ter pelo menos 5 caracteres”);
```
 } 
     this.login = login;
```
}

public String getSenha(){
return senha;
}

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

}

rrodriguessarri · Novembro 25, 2017, 3:02pm

/*

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 br.com.lojavirtual.controle;

import br.com.lojavirtual.modelo.Usuario;
import br.com.lojavirtual.modelo.UsuarioDao;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
*

@author rafael
*/
public class ControllerUsuario extends HttpServlet {

/**

Processes requests for both HTTP GET and POST
methods.
@param request servlet request
@param response servlet response
@throws ServletException if a servlet-specific error occurs

@throws IOException if an I/O error occurs
*/
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType(“text/html;charset=UTF-8”);

try (PrintWriter out = response.getWriter()) {

 Usuario usuario = new Usuario();

 UsuarioDao usuarioDao = new UsuarioDao();

 String flag = request.getParameter("flag");

 try {
     int conexao = usuarioDao.conectar();
     if (conexao == 0) {
         if (flag.equals("CadastrarUsuario")) {

             String nome = request.getParameter("txtnome");
             String telefone = request.getParameter("txttelefone");
             String email = request.getParameter("txtemail");
             String senha = request.getParameter("txtsenha");
             String login = request.getParameter("txtlogin");

             usuario.setNome(nome);
             usuario.setEmail(email);
             usuario.setTelefone(telefone);
             usuario.setLogin(login);
             usuario.setSenha(senha);

             int cadastro = usuarioDao.inserir(usuario.getNome(), usuario.getEmail(), usuario.getTelegone(), usuario.getLogin(), usuario.getSenha());
             
             if (cadastro == 0) {
                 request.setAttribute("mensagem", "Usuário cadastrado com sucesso");
                 getServletContext().getRequestDispatcher("/cadastro.jsp").include(request, response);
             } else {
                 request.setAttribute("mensagem","Cliente nao cadastrado");
                 getServletContext().getRequestDispatcher("/cadastro.jsp").include(request, response);

             }
         
         }
     }
 } catch (IllegalArgumentException e) {
     out.write(e.getMessage());
     
 } finally {
     usuarioDao.desconectar();
 }
 
 List listaUsuario = usuarioDao.pesquisar();
 request.setAttribute("ListaUsuario", listaUsuario);
 RequestDispatcher rd = request.getRequestDispatcher("/usuarioPesquisa.jsp");
 rd.forward(request, response);

}

//
/**

Handles the HTTP GET method.
@param request servlet request
@param response servlet response
@throws ServletException if a servlet-specific error occurs
@throws IOException if an I/O error occurs
*/
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);
}

/**

Handles the HTTP POST method.
@param request servlet request
@param response servlet response
@throws ServletException if a servlet-specific error occurs
@throws IOException if an I/O error occurs
*/
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);
}

/**

Returns a short description of the servlet.
@return a String containing servlet description
*/
@Override
public String getServletInfo() {
return “Short description”;
}//

}

rrodriguessarri · Novembro 25, 2017, 3:04pm

A view

<%@page import=“br.com.lojavirtual.modelo.Usuario”%>
<%@page import=“java.util.Iterator”%>
<%@page import=“br.com.lojavirtual.modelo.UsuarioDao”%>
<%@page import=“java.util.List”%>
<!doctype html>

<head>
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
    <title>Tec Fontes</title>
    <meta name="description" content="">
    <!--<meta http-equiv="Refresh" content="0; URL=login.html">-->
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel="icon" type="image/png" href="imagens/ms-icon-144x144.png">

    <link rel="stylesheet" href="css/bootstrap.min.css">
    
    <link rel="stylesheet"  href="css/estilo.css">
    
    <link rel="stylesheet" href="css/bootstrap-theme.min.css">
    <link rel="stylesheet" href="css/main.css">

    <script src="js/vendor/modernizr-2.8.3-respond-1.4.2.min.js"></script>
</head>

 <body>

    
    <nav class="navbar navbar-fixed-top navbar-inverse navbar-transparente">
        <div class="container">
            
            <!-- header-->
            <div class="navbar-header">
                
                <!--botao para celular-->
                <button type="button" class="navbar-toggle collapsed"
                        data-toggle="collapse" data-target="#barra-navegacao">
                    <span class="sr-only">Alternar navegação</span>
                    <span class="icon-bar"></span>
                    <span class="icon-bar"></span>
                    <span class="icon-bar"></span>
                    <span class="icon-bar"></span>
                </button>
                
                <a href="index.html" class="navbar-brand">
                    <span class="img-logo"></span>
                </a>
            </div>
            
            <!--barra menu-->
            <div class="collapse navbar-collapse" id="barra-navegacao">
                <ul class="nav navbar-nav navbar-right">
                    <li><a href="index.html">Central do sistema</a></li>
                    <li><a href="cadastro.jsp.html">Cadastro</a></li>
                    <li><a href="#">Compras </a></li>
                    <li class="divisor" role="separator"></li>
                    <li><a href="Ajuda.html">Versão</a></li>
                </ul>
            </div><!--/barra menu-->
        </div><!--/container-->
    </nav>
    
    <div class="row">
        <div class="col-sm-6">
            <br><br>
            <h2>Usuários</h2>
        </div>
        
        <form action="ControllerUSuario" method="post">
        <div class="col-sm-6 text-right h2">
            <br><br>
            <button type="submit" class="btn-lg btn-primary" href="index.html">
                <i class="fa fa-plus"></i>Voltar</button>
                <button type="submit" class="btn-lg btn-danger" href="ControllerUsuario">
                    <i class="fa fa-refresh"></i>Atualizar</button>
        </div>
    </div>
    
    
    <hr>
    
    <table class="table table-hover">
        <thead>
            <tr>
                <th>Id</th>
                <th width="30%">Nome</th>
                <th>Telefone</th>
                <th>Opções</th>
                
            </tr>
       </thead>
       <tbody>
           <%
               List lista = (List) request.getAttribute("ListaUsuario");
               for(Iterator iterator = lista.iterator(); iterator.hasNext();){
                   Usuario usuarios = (Usuario) iterator.next();%>
            <tr>
                <th><%= usuarios.getNome()%></th>
                <th><%= usuarios.getEmail()%></th>
                <th><%= usuarios.getTelegone()%></th>
                
            </tr>
            <%
               }
            %> 
        </tbody>
    </table>
   </form>
            
            
        
    </body>

rrodriguessarri · Novembro 25, 2017, 3:07pm

Ele está dando nullPointerExecption no array mas não sei oque faço, para resolver isso

ArrayList NullPointerExcepti on, Estou tentando trazer uma lista de usuários para minha view e está dando NullPointerException

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