1
I’m doing a library project, I register Book, Publisher and Parents and then I display them on JSP. When I register the data appear normally in JSP but if I refresh the page they are re-registered. I have never used Servlet and JSP before.
Servlet:
package br.com.wesley.libna.controller;
import br.com.wesley.libna.database.CadastrarDataBase;
import br.com.wesley.libna.database.Conexao;
import java.io.IOException;
import java.util.ArrayList;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet(name = "Carregar", urlPatterns = {"/Carregar"})
public class Carregar extends HttpServlet {
private final CadastrarDataBase cad;
public Carregar() {
this.cad = new CadastrarDataBase();
}
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
Conexao con = new Conexao();
con.conectar();
RequestDispatcher rd = null;
if (con.estaConectado()) {
ArrayList<String> paises = this.listaPaises(con);
ArrayList<String> editoras = this.listaEditoras(con);
request.setAttribute("paises", paises);
request.setAttribute("editoras", editoras);
request.setAttribute("resultado", false);
rd = request.getRequestDispatcher("cadastrar.jsp");
}
rd.forward(request, response);
}
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);
}
@Override
public String getServletInfo() {
return "Short description";
}// </editor-fold>
public ArrayList<String> listaPaises(Conexao con) {
cad.processarListaDePaises(con.getStm());
return cad.getPais();
}
public ArrayList<String> listaEditoras(Conexao con) {
cad.processarListaDeEditoras(con.getStm());
return cad.getEditora();
}
}
JSP:
<%@page import="br.com.wesley.libna.database.Conexao"%>
<%@page import="br.com.wesley.libna.database.CadastrarDataBase"%>
<%@page import="java.util.ArrayList"%>
<%
ArrayList<String> paises = (ArrayList) request.getAttribute("paises");
ArrayList<String> editoras = (ArrayList) request.getAttribute("editoras");
%>
<html>
<head>
<title>Cadastrar | Libna</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<script type="text/javascript" src="js\jquery-3.3.1.min.js"></script>
<script type="text/javascript" src="js\bootstrap.min.js"></script>
<link rel="stylesheet" type="text/css" href="css\style.css" />
<link rel="stylesheet" type="text/css" href="css\bootstrap.min.css" />
</head>
<body onload="exibir_ocultar(this)">
<nav class="navbar navbar-expand-md bg-dark navbar-dark">
<a class="navbar-brand" href="#">Libna</a>
<button class="navbar-toggler" type="button" data-toggle="collapse"
data-target="#collapsibleNavbar">
<span class="navbar-toggler-icon"></span>
</button>
<div class="collapse navbar-collapse" id="collapsibleNavbar">
<ul class="navbar-nav">
<li class="nav-item"><a class="nav-link" href="cadastrar.jsp">Cadastrar</a></li>
<li class="nav-item"><a class="nav-link" href="#">Consultar</a></li>
<li class="nav-item"><a class="nav-link" href="sobre.jsp">Sobre</a></li>
</ul>
</div>
</nav>
<div class="container">
<div class="row coluna">
<%
boolean resultado = (Boolean) request.getAttribute("resultado");
if (resultado) {
boolean inseriu = (Boolean) request.getAttribute("inseriu");
if (inseriu) {
out.println("<div class='alert alert-success alert-dismissible col-md-12'>");
out.println("<button type='button' class='close' data-dismiss='alert'>×</button>");
out.println("<strong>" + request.getAttribute("frase") + "</strong>");
out.println("</div>");
} else {
out.println("<div class='alert alert-danger alert-dismissible col-md-12'>");
out.println("<button type='button' class='close' data-dismiss='alert'>×</button>");
out.println("<strong>" + request.getAttribute("frase") + "</strong>");
out.println("</div>");
}
}
%>
</div>
<div class="row coluna">
<div class="col-md-12">
<h2 class="text-success">O que deseja cadastrar?</h2>
</div>
</div>
<div class="row coluna">
<div class="checkbox col-md-12">
<select class="form-control" id="tipoCadastro" name="tipoCadastro" onchange="exibir_ocultar(this)">
<option>Livro</option>
<option>Pais</option>
<option>Autor</option>
<option>Editora</option>
</select>
</div>
</div>
<div class="row view-pais coluna" id="view-pais">
<div class="col-md-12">
<form action="Pais" method="POST">
<div class="form-group">
<label for="nome">Nome:</label>
<input type="text" class="form-control" id="nome" placeholder="Digite o nome do pais" name="nome">
</div>
<button type="submit" class="btn btn-primary">CADASTRAR</button>
</form>
</div>
</div>
<div class="row view-editora coluna" id="view-editora">
<div class="col-md-12">
<form action="Editora" method="POST">
<div class="form-group">
<label for="email">Nome:</label>
<input type="text" class="form-control" id="nome" placeholder="Digite o nome da editora" name="nome">
</div>
<div class="form-group">
<label for="nomePais">Pais:</label>
<select class="form-control" id="nomePais" name="nomePais">
<%
for (String p : paises) {
out.print("<option>" + p + "</option>");
}
%>
</select>
</div>
<button type="submit" class="btn btn-primary">CADASTRAR</button>
</form>
</div>
</div>
<div class="row view-editora coluna" id="view-livro">
<div class="col-md-12">
<form action="Editora" method="POST">
<div class="form-group">
<label for="email">Nome:</label>
<input type="text" class="form-control" id="nome" placeholder="Digite o nome do livro" name="nome">
</div>
<div class="form-group">
<label for="nomePais">Pais:</label>
<select class="form-control" id="nomePais" name="nomePais">
<%
for (String p : paises) {
out.print("<option>" + p + "</option>");
}
%>
</select>
</div>
<div class="form-group">
<label for="nomePais">Editora:</label>
<select class="form-control" id="nomeEditora" name="nomeEditora">
<%
for (String e : editoras) {
out.print("<option>" + e + "</option>");
}
%>
</select>
</div>
<button type="submit" class="btn btn-primary">CADASTRAR</button>
</form>
</div>
</div>
</div>
</body>
<script type="text/javascript">
function exibir_ocultar() {
var valor = $("#tipoCadastro").val();
$('#view-editora').hide();
$('#view-pais').hide();
$('#view-livro').hide();
if (valor == "Pais") {
$('#view-pais').show();
} else if (valor == 'Editora') {
$('#view-editora').show();
} else if (valor == 'Livro') {
$('#view-livro').show();
}
}
</script>
</html>
Maybe the problem is
rd.forward: https://www.codebyamir.com/blog/java-servlet-essentials-sendredirect-vs-forward– hkotsubo
using Response.sendRedirect() the data will pass ?
– user71502