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   <title>Configuring HTTP/2 Push</title><link rel="stylesheet" type="text/css" href="css/docbook.css"><meta name="generator" content="DocBook XSL Stylesheets V1.79.1"><meta name="keywords" content="jetty, servlet, servlet-api, cometd, http, websocket, eclipse, maven, java, server, software"><link rel="home" href="index.html" title="Jetty"><link rel="up" href="http2.html" title="Chapter&nbsp;16.&nbsp;HTTP/2"><link rel="prev" href="http2-configuring.html" title="Configuring HTTP/2"><link rel="next" href="http2-configuring-haproxy.html" title="Configuring HAProxy and Jetty"><link xmlns:jfetch="java:org.eclipse.jetty.xslt.tools.JavaSourceFetchExtension" xmlns:fetch="java:org.eclipse.jetty.xslt.tools.SourceFetchExtension" xmlns:d="http://docbook.org/ns/docbook" xmlns:l="http://docbook.sourceforge.net/xmlns/l10n/1.0" xmlns:xslthl="http://xslthl.sf.net" xmlns:gcse="http://www.google.com" xmlns:date="http://exslt.org/dates-and-times" rel="shortcut icon" href="images/favicon.ico"><link rel="stylesheet" href="css/highlighter/foundation.css"><script src="js/highlight.pack.js"></script><script>
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            Version: 9.3.28.v20191105</span></td><td style="width: 50%"></td></tr></table><div xmlns:jfetch="java:org.eclipse.jetty.xslt.tools.JavaSourceFetchExtension" xmlns:fetch="java:org.eclipse.jetty.xslt.tools.SourceFetchExtension" xmlns:d="http://docbook.org/ns/docbook" xmlns:l="http://docbook.sourceforge.net/xmlns/l10n/1.0" xmlns:xslthl="http://xslthl.sf.net" xmlns:gcse="http://www.google.com" xmlns:date="http://exslt.org/dates-and-times" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Configuring HTTP/2 Push</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="http2-configuring.html"><i class="fa fa-chevron-left" aria-hidden="true"></i> Previous</a>&nbsp;</td><th width="60%" align="center">Chapter&nbsp;16.&nbsp;HTTP/2<br><a accesskey="p" href="index.html"><i class="fa fa-home" aria-hidden="true"></i> Home</a></th><td width="20%" align="right">&nbsp;<a accesskey="n" href="http2-configuring-haproxy.html">Next <i class="fa fa-chevron-right" aria-hidden="true"></i></a></td></tr></table><hr></div><div xmlns:jfetch="java:org.eclipse.jetty.xslt.tools.JavaSourceFetchExtension" xmlns:fetch="java:org.eclipse.jetty.xslt.tools.SourceFetchExtension" xmlns:d="http://docbook.org/ns/docbook" xmlns:l="http://docbook.sourceforge.net/xmlns/l10n/1.0" xmlns:xslthl="http://xslthl.sf.net" xmlns:gcse="http://www.google.com" xmlns:date="http://exslt.org/dates-and-times" class="jetty-callout"><h5 class="callout"><a href="http://www.webtide.com/">Contact the core Jetty developers at
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      </p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="http2-configuring-push"></a>Configuring HTTP/2 Push</h2></div></div></div><p>HTTP/2 Push is a mechanism that allows the server to send multiple resources to the client for a single client request.
This will reduce the amount of round-trips necessary to retrieve all the resources that make up a web page and can significantly improve the page load time.</p><p>HTTP/2 Push can be automated in your application by configuring a <a class="link" href="http://www.eclipse.org/jetty/javadoc/9.3.28.v20191105/org/eclipse/jetty/servlets/PushCacheFilter.html" target="_top"><code class="literal">PushCacheFilter</code></a> in the <code class="literal">web.xml</code>, in this way:</p><pre xmlns:jfetch="java:org.eclipse.jetty.xslt.tools.JavaSourceFetchExtension" xmlns:fetch="java:org.eclipse.jetty.xslt.tools.SourceFetchExtension" xmlns:d="http://docbook.org/ns/docbook" xmlns:l="http://docbook.sourceforge.net/xmlns/l10n/1.0" xmlns:xslthl="http://xslthl.sf.net" xmlns:gcse="http://www.google.com" xmlns:date="http://exslt.org/dates-and-times"><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;web-app
    xmlns="http://xmlns.jcp.org/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
    metadata-complete="true"
    version="3.1"&gt;

    ...
    &lt;filter&gt;
        &lt;filter-name&gt;PushFilter&lt;/filter-name&gt;
        &lt;filter-class&gt;org.eclipse.jetty.servlets.PushCacheFilter&lt;/filter-class&gt;
        &lt;async-supported&gt;true&lt;/async-supported&gt;
    &lt;/filter&gt;
    &lt;filter-mapping&gt;
        &lt;filter-name&gt;PushFilter&lt;/filter-name&gt;
        &lt;url-pattern&gt;/*&lt;/url-pattern&gt;
    &lt;/filter-mapping&gt;
    ...

&lt;/web-app&gt;</code></pre><p><code class="literal">PushCacheFilter</code> analyzes the HTTP requests for resources that arrive to your web application.
Some of these requests contain the HTTP <code class="literal">Referrer</code> header that points to a resource that has been requested previously.
This allows the <code class="literal">PushCacheFilter</code> to organize resources in to two categories: <span class="emphasis"><em>primary</em></span> resources (those referenced by the <code class="literal">Referrer</code> header) and <span class="emphasis"><em>secondary</em></span> resources (those that have the <code class="literal">Referer</code> header).</p><p><code class="literal">PushCacheFilter</code> associates secondary resources to primary resources.
Only secondary resources that have been requested within a time window from the request of the primary resource are associated with the primary resource.</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">PushCacheFilter</code> can be configured with the following <code class="literal">init-params</code></span></dt><dd><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><code class="literal">associatePeriod</code>: the time window, in milliseconds, within which a request for a secondary resource will be associated to a primary resource.</li><li class="listitem"><code class="literal">maxAssociations</code>: the max number of secondary resources that may be associated to a primary resource.</li></ul></div></dd></dl></div></div><script type="text/javascript">
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