Clever Geek Handbook

Páginas XML de carregamento progressivo

O carregamento progressivo de páginas XML está carregando e exibindo simultaneamente partes já carregadas e processadas de uma página XML enquanto o modelo XSLT ainda está processando o restante das partes.

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Temos um XML muito grande. Este é um artigo com muitos comentários. Em uma Internet móvel lenta e instável, você pode não esperar que carregue. Durante o download, a conexão é interrompida e o XML permanece não carregado. Parece que você pode apenas atualizar a página e o navegador carregará apenas a parte que falta. Mas não. O navegador carrega a página novamente e novamente falha e vemos um erro em vez da página.



Mas há uma saída para essa situação. Vamos dividir o XML em pequenos pedaços que terão tempo para carregar em um canal lento e entrar no cache. Como bônus, temos proteção contra subcarga e carregamento progressivo.



Com o que vamos trabalhar



Artigo XML



Este arquivo contém um título, uma descrição, o texto do artigo e muitos, muitos comentários. Mais precisamente, existem 5962 comentários.



Cada comentário possui um atributo 'índice'. Este índice é usado por outros comentários no atributo 'on' para indicar que o comentário é uma resposta ao comentário cujo índice é especificado.



lorem-ipsum.xml 
<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet  href=".xslt" type="text/xsl"?>
<>
    <title xmlns="http://www.w3.org/1999/xhtml">Lorem Ipsum</title>
    <meta name="description" content="Neque porro quisquam est qui dolorem ipsum quia dolor sit amet, consectetur, adipisci velit..." xmlns="http://www.w3.org/1999/xhtml"/>
    <>Quisque sollicitudin malesuada urna, id tincidunt quam. Pellentesque luctus, sem vel posuere efficitur, est enim pulvinar orci, et vulputate orci dui a libero. Nam eget mauris sed diam pretium fermentum. Proin euismod ultrices justo, non aliquet ipsum bibendum at. Duis eget laoreet mauris. Morbi tristique arcu libero, quis pharetra justo bibendum eget. In at quam sed lacus vestibulum tincidunt quis ut ex.</>
    < ="1">
Nunc sit amet ligula mauris. Integer vel nisi ac turpis rhoncus suscipit. Fusce elementum ut elit quis rutrum. Nulla bibendum placerat ex pulvinar accumsan. Praesent vestibulum hendrerit accumsan. Sed quis ligula pretium, condimentum enim in, cursus elit. Phasellus quis mauris arcu. Integer congue ex et ante porttitor vestibulum. Donec vel mauris venenatis, ultrices leo in, dapibus metus. Morbi pharetra eleifend libero nec efficitur. Fusce efficitur et ligula quis scelerisque. Curabitur eget nibh at nunc lacinia fringilla et eget quam. Praesent malesuada, odio in pulvinar semper, libero nunc consectetur lorem, vel egestas erat tellus nec ipsum.
</>
<!-- ... -->
    < ="1" ="4">
Praesent varius vitae arcu sed imperdiet. Proin pulvinar a augue blandit scelerisque. Pellentesque lectus erat, gravida lobortis lorem ut, dignissim tempor felis. Nunc porttitor libero quis est sodales, non ornare metus eleifend. Cras orci lacus, auctor non sollicitudin lacinia, ultricies vitae diam. Fusce eu leo varius, interdum sapien ac, vestibulum orci. Sed placerat feugiat odio, vitae tempor tellus volutpat tincidunt. Cras dapibus est et mi euismod ornare. Vestibulum accumsan justo non volutpat dictum. Curabitur porttitor, magna id euismod tincidunt, metus nisl fermentum tellus, id pulvinar leo nibh vel velit. Sed gravida gravida sapien et porttitor. Nam volutpat, ex id faucibus commodo, arcu arcu fringilla mi, et volutpat nunc turpis at ligula. Pellentesque et vulputate ligula, lobortis dignissim ligula. Nulla laoreet auctor ultricies. Interdum et malesuada fames ac ante ipsum primis in faucibus.
</>
<!-- ...     -->
</>


Modelo XSLT básico



Este é um pequeno modelo XSLT que converte XML em xHTML completo e monta tópicos de comentários de uma lista.



article.xslt 
<xsl:stylesheet
  version="1.0"
  xmlns="http://www.w3.org/1999/xhtml"
  xmlns:x="http://www.w3.org/1999/xhtml"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:output method="xml" indent="yes" encoding="UTF-8"/>

    <!--       -->
    <xsl:key name="" match="" use="@"/>

    <!--   -->
    <xsl:template match="node()|@*">
        <xsl:copy>
            <xsl:apply-templates select="node()|@*" />
        </xsl:copy>
    </xsl:template>

    <!--  xHTML  -->
    <xsl:template match="">
        <html>
            <head>
                <!--          xHTML  title  meta -->
                <!--        -->
                <xsl:copy-of select="x:title | x:meta[@name = 'description']"/>

                <style>
                    . {
                        padding: 1vw;
                        min-width: 20em;
                        border: 1px solid gray;
                        color: black;
                        background-color: white;
                    }

                    . {
                        max-width: 46em; 
                        margin: auto;
                        text-align: justify;
                    }
                </style>
            </head>
            <body>
                <!--  (     )-->
                <xsl:apply-templates select="@*" />
                <div class="">
                    <!--    'title'    -->
                    <h1><xsl:value-of select="x:title"/></h1>

                    <!--  'content'  'meta'     -->
                    <i><xsl:value-of select="x:meta[@name = 'description']/@content"/></i>

                    <!--    ''     -->
                    <p><xsl:apply-templates select="/node()" /></p>
                </div>

                <!--       -->
                <xsl:apply-templates select="." mode=""/>
            </body>
        </html>
    </xsl:template>

    <!--         -->
    <xsl:template match="" mode="">
        <details id="" open=''>
            <summary></summary>

            <!--       @   --> 
            <xsl:apply-templates select="[not(@)]"/>
        </details>
    </xsl:template>

    <!--   -->
    <xsl:template match="">
        <!--   ""      -->
        <div class="" id="{@}">

            <!--     -->
            <xsl:apply-templates select="@*" />

            <!--        -->
            <a href="#{@}"><xsl:value-of select="@"/></a><xsl:text>: </xsl:text>

            <div class="">
                <!--    -->
                <xsl:apply-templates select="node()" /> 
            </div>

            <!--      -->
            <xsl:apply-templates select="." mode=""/> 
        </div>
    </xsl:template>

    <!--         -->
    <xsl:template match="" mode="">
        <!--       -->
        <xsl:if test="key('', @)">
            <details open=''>
                <summary></summary>

                <!--   -->
                <xsl:apply-templates select="key('', @)"/>
            </details>
        </xsl:if>
    </xsl:template>
</xsl:stylesheet>


Testando



Defina o limite de velocidade GPRS no navegador. Abrimos a página e vamos tomar um chá. A tela exibirá a página anterior até que todo o arquivo XML seja carregado e o modelo XSLT executado.



lorem-ipsum.xml



Carga completa: 10,77 min



Processando e dividindo o arquivo XML



Precisamos dividir o artigo em uma parte com o texto do artigo e várias partes que conterão comentários.



.



XML , XSLT .





XML '-', XML , .



xslt\--.xslt:



<xsl:stylesheet
  version="1.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:output method="xml" encoding="UTF-8"/>

    <xsl:key name="" match="" use="@"/> 

    <!--     -->
    <xsl:param name="" />

    <!--   -->
    <xsl:template match="node()|@*">
        <xsl:copy>
            <xsl:apply-templates select="node()|@*" />
        </xsl:copy>
    </xsl:template>

    <!--    -->
    <xsl:template match="">

        <!--     -->
        <xsl:param name="-" select="floor(@ div $)" />

        <!--      -->
        <xsl:param name="-" select="key('', @)[floor(@ div $) > $-]"/>

        <!--   -->
        <xsl:copy>
            <!--   ""  "" -->
            <xsl:apply-templates select="@*" />

            <!--       -->
            <xsl:if test="$-">
                <!--   "-" -->
                <xsl:attribute name="-">
                    <!--       -->
                    <xsl:call-template name="-">

                        <!--      -->
                        <xsl:with-param name="" select="$-" />

                    </xsl:call-template>
                </xsl:attribute>
            </xsl:if>

            <!--       -->
            <xsl:apply-templates select="node()" />
        </xsl:copy>
    </xsl:template>

    <xsl:template name="-">
        <!--       -->
        <xsl:param name=""/>

        <!--    -->
        <xsl:param name="-" select="floor($[1]/@ div $)"/>

        <!--      -->
        <xsl:param name="-" select="$[floor(@ div $) > $-]"/>

        <!--     -->
        <xsl:value-of select="$-"/>

        <!--       -->
        <xsl:if test="$-">
            <!--      -->
            <xsl:text> </xsl:text>

            <!--     -->
            <xsl:call-template name="-">
                <!--      -->
                <xsl:with-param name="" select="$-" />
            </xsl:call-template>
        </xsl:if>
    </xsl:template>
</xsl:stylesheet>


XML



.



xslt\--.xslt:



<xsl:stylesheet
  version="1.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

    <!--           'method'  'text' -->
    <xsl:output method="text" encoding="UTF-8"/>

    <!--     XML  -->
    <xsl:param name="" select="100" />

    <xsl:template match="/">
        <!--      XML  -->
        <xsl:value-of select="floor(count(//) div $)"/>
    </xsl:template>

</xsl:stylesheet>




('') XML .



xslt\-.xslt:



<xsl:stylesheet
  version="1.0"
  xmlns:x="http://www.w3.org/1999/xhtml"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:output method="xml" encoding="UTF-8"/>

    <xsl:param name="" />

    <!--     -->
    <xsl:param name=""/>

    <!--       -->
    <xsl:param name=""/>

    <xsl:template match="/">
        <!--           -->
        <xsl:processing-instruction name="xml-stylesheet">href="../-.xslt" type="text/xsl"</xsl:processing-instruction>

        <!--     -->
        <xsl:apply-templates select="" />
    </xsl:template>

    <xsl:template match="">
        < ="{$}">
            <!--  title  meta  -->
            <xsl:copy-of select="x:title | x:meta[@name = 'description']"/>

            <!--       -->
            <xsl:copy-of select="[floor(@ div $) = $]" />
        </>
    </xsl:template>
</xsl:stylesheet>




, .



xslt\-.xslt:



<xsl:stylesheet
  version="1.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:output method="xml" encoding="UTF-8"/>

    <!--   -->
    <xsl:template match="node()|@*">
        <xsl:copy>
            <xsl:apply-templates select="node()|@*" />
        </xsl:copy>
    </xsl:template>

    <xsl:template match="/">
        <!--     -->
        <xsl:processing-instruction name="xml-stylesheet">href="../-.xslt" type="text/xsl"</xsl:processing-instruction>

        <!--     -->
        <xsl:apply-templates select="" />
    </xsl:template>

    <!--    -->
    <xsl:template match=""/>
</xsl:stylesheet>


msxsl.exe



msxsl.exe. XML XSLT stdout .



CMD



XML .



progressive.cmd lorem-ipsum.xml 100



progressive.cmd:



chcp 65001

rem      XML   
md "%~dpn1"

rem    
msxsl.exe %1 "%~dp0xslt\--.xslt" -xw -o "%~dpn1\index.xml" =%2

rem    XML   
for /f "delims=" %%a in ('msxsl.exe %1 ^"%~dp0xslt\--.xslt^" ^=%2') do set =%%a

rem    
for /l %%i in (0,1,%%) do msxsl.exe -o "%~dpn1\%%i.xml" "%~dpn1\index.xml" "%~dp0xslt\-.xslt" =%2 =%%i ="%~n1"

rem    
msxsl.exe "%~dpn1\index.xml" "%~dp0xslt\-.xslt" -o "%~dpn1\index.xml"






. . .



-.xslt



<xsl:stylesheet
  version="1.0"
  xmlns="http://www.w3.org/1999/xhtml"
  xmlns:x="http://www.w3.org/1999/xhtml"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:output method="xml" indent="yes" encoding="UTF-8"/>

    <!--   ".xslt" -->
    <xsl:include href="%D1%81%D1%82%D0%B0%D1%82%D1%8C%D1%8F.xslt"/>

    <xsl:template match="" mode="">

        <!--          -->
        <iframe style="display:none;" id="-" src="0.xml"/>

        <script><![CDATA[
            setTimeout(function(){
                var  = document.querySelector("#-");
                if ( && .contentDocument)
                {
                    var  = .contentDocument.getElementById('');

                    //       
                    if ()
                    {
                        //      
                        document.body.appendChild();
                        return;
                    }
                }

                //   Timeout     
                setTimeout(arguments.callee, 100);
            }, 100)]]>
        </script>
        <noscript>
            <!--     JavaScript         -->
            <a href="0.xml"></a>
        </noscript>
    </xsl:template>
</xsl:stylesheet>




XML .



-.xslt



<xsl:stylesheet
  version="1.0"
  xmlns="http://www.w3.org/1999/xhtml"
  xmlns:x="http://www.w3.org/1999/xhtml"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:output method="html" indent="yes" encoding="UTF-8"/>

    <!--   ".xslt" -->
    <xsl:include href="%D1%81%D1%82%D0%B0%D1%82%D1%8C%D1%8F.xslt"/>

    <!--            -->
    <xsl:key name="" match="" use="@"/>

    <xsl:param name="" select="/@"/>

    <xsl:template match="/">
        <!--    ".xslt" -->
        <xsl:apply-templates select="document(concat($, '/index.xml'))/"/>
    </xsl:template>

    <!--       -->
    <xsl:template match="" mode="">
        <details id="" open=''>
            <!--             -->
            <summary></summary>

            <!--    -->
            <xsl:call-template name="-"/>
        </details>
    </xsl:template>

    <xsl:template name="-">

        <!--   XML   0 -->
        <xsl:param name="" select="0"/>

        <!--  XML -->
        <xsl:param name="" select="document(concat($, '/', $, '.xml'))"/>

        <!--  XML  -->
        <xsl:if test="$">

            <!--      -->
            <xsl:apply-templates select="$//[not(@)]" />

            <!--     XML  -->
            <xsl:call-template name="-">
                <!--    XML -->
                <xsl:with-param name="" select="$ + 1" />
            </xsl:call-template>
        </xsl:if>
    </xsl:template>

    <!--          -->
    <xsl:template match="" mode="">
        <!--         XML     -->
        <xsl:if test="key('', @) or @-">
            <details open=''>
                <summary></summary>

                <!--     XML -->
                <xsl:apply-templates select="key('', @)"/>

                <!--      XML -->
                <xsl:call-template name="-"/>
            </details>
        </xsl:if>
    </xsl:template>

    <xsl:template name="-">
        <!--     -->
        <xsl:param name="" select="concat(@-, ' ')"/>

        <!--     -->
        <xsl:param name="" select="substring-before($, ' ')"/>

        <!--      -->
        <xsl:if test="$">

            <!--  XML -->
            <xsl:apply-templates select="document(concat($, '/', $, '.xml'))" mode="">
                <!--         -->
                <xsl:with-param name="" select="@"/>
            </xsl:apply-templates>

            <!--      -->
            <xsl:call-template name="-">

                <!--     -->
                <xsl:with-param name="" select="substring-after($, ' ')"/>
            </xsl:call-template>
        </xsl:if>
    </xsl:template>

    <xsl:template match="/" mode="">
        <!--         -->
        <xsl:param name=""/>

        <!--       -->
        <xsl:apply-templates select="key('', $)"/>
    </xsl:template>

</xsl:stylesheet>




GPRS .



lorem-ipsum/index.xml



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