Access-Control-Allow-Origin jQuery Ajax

Question

I am trying to access the mail api to calculate freight and get the following msg:

Failed to load 
http://ws.correios.com.br/calculador/CalcPrecoPrazo.asmx/CalcPrecoPrazo: No 
'Access-Control-Allow-Origin' header is present on the requested resource. 
Origin 'http://site.com' is therefore not allowed access.

my ajax:

          var params = {
                'nCdEmpresa': '',
                'sDsSenha': '',
                'nCdServico': '04014',
                'sCepOrigem': '03638010',
                'sCepDestino': '43810040',
                'nVlPeso': '1',
                'nCdFormato': '1',
                'nVlComprimento': '16',
                'nVlAltura': '5',
                'nVlLargura': '15',
                'nVlDiametro': '0',
                'sCdMaoPropria': 'n',
                'nVlValorDeclarado': '0',
                'sCdAvisoRecebimento': 'n',
                'StrRetorno': 'xml',
                'nCdServico': '40010,41106'
            };

        $.ajax({
            type: "POST",
            url: "http://ws.correios.com.br/calculador/CalcPrecoPrazo.asmx/CalcPrecoPrazo",
            data: params,
            dataType : "xml",
            success: function (data) {
                console.log(JSON.stringify(data));
            }
        });

Answer 1

I don’t know if it’s impossible, but you can access the Mail API next to the server. If you are using PHP create a file, example: php.

/* Recupere os dados enviados via POST
 * Documentação: https://secure.php.net/manual/en/function.filter-input-array.php
 */
$DADOS = filter_input_array(INPUT_POST);
/* Utilize a função 'http_build_query' para construir a string de consulta
 * Documentação: http://php.net/manual/en/function.http-build-query.php
 * 
 * Utilize a função 'simplexml_load_file' para carregar os dados da API
 * Documentação: http://php.net/manual/en/function.simplexml-load-file.php
 */
$resultado = simplexml_load_file( 'http://ws.correios.com.br/calculador/CalcPrecoPrazo.aspx?' . http_build_query($DADOS) );
echo json_encode($resultado);

Then just make the requisition:

<h2>Frete:</h2>
<div id="frete"></div>
<script src="https://code.jquery.com/jquery-2.2.4.js"></script>
<script>
    $(document).ready(function() {
        var params = {
            'nCdEmpresa': '',
            'sDsSenha': '',
            'nCdServico': '40010,41106',
            'sCepOrigem': '03638010',
            'sCepDestino': '43810040',
            'nVlPeso': '1',
            'nCdFormato': '1',
            'nVlComprimento': '16',
            'nVlAltura': '5',
            'nVlLargura': '15',
            'nVlDiametro': '0',
            'sCdMaoPropria': 'n',
            'nVlValorDeclarado': '0',
            'sCdAvisoRecebimento': 'n',
            'StrRetorno': 'xml',
        };

        $.ajax({
            type: "POST",
            url: "calcula_frete.php",
            data: params,
            success: function(data) {
                var j = JSON.parse(data);
                for (var i = 0; i < j.cServico.length; i++) {
                    $('#frete').append(' \
<div>Código: <b>' + j.cServico[i].Codigo + '</b></div> \
<div>Valor: <b>' + j.cServico[i].Valor + '</b></div> \
<div>Prazo entrega: <b>' + j.cServico[i].PrazoEntrega + '</b></div><br>');
                }
            }
        });
    });
</script>

References

• filter_input_array
• http_build_query
• simplexml_load_file

Answer 2

If I understand correctly you are doing an Xmlhttprequest for a different domain than your page is (Post Office). Therefore, the browser is blocking this as it normally allows a request from the same source for security reasons. You need to do something different when you want to make a cross-domain request using CORS.

Regular web pages may use the Xmlhttprequest object to send and receive data from remote servers, but they are limited by the same source policy. Extensions are not so limited. An extension can talk to remote servers outside of their origin, provided it first requests cross-source permissions.

Increment your Ajax code:

<script>
  var params = {
                'nCdEmpresa': '',
                'sDsSenha': '',
                'nCdServico': '04014',
                'sCepOrigem': '03638010',
                'sCepDestino': '43810040',
                'nVlPeso': '1',
                'nCdFormato': '1',
                'nVlComprimento': '16',
                'nVlAltura': '5',
                'nVlLargura': '15',
                'nVlDiametro': '0',
                'sCdMaoPropria': 'n',
                'nVlValorDeclarado': '0',
                'sCdAvisoRecebimento': 'n',
                'StrRetorno': 'xml',
                'nCdServico': '40010,41106'
            };

$.ajax({
    url: 'http://ws.correios.com.br/calculador/CalcPrecoPrazo.asmx/CalcPrecoPrazo',
    data: params,
    type: 'GET',
    crossDomain: true,
    dataType: 'jsonp',
    success: function() { alert("Success"); },
    error: function() { alert('Failed!'); },
    beforeSend: setHeader
});
</script>

If that’s what I understand, then it should work.