292 lines
12 KiB
HTML
292 lines
12 KiB
HTML
<!DOCTYPE html>
|
|
<!--[if IE 8]><html class="no-js lt-ie9" lang="en" > <![endif]-->
|
|
<!--[if gt IE 8]><!--> <html class="no-js" lang="en" > <!--<![endif]-->
|
|
<head>
|
|
<meta charset="utf-8">
|
|
<meta http-equiv="X-UA-Compatible" content="IE=edge">
|
|
<meta name="viewport" content="width=device-width, initial-scale=1.0">
|
|
|
|
|
|
<link rel="shortcut icon" href="../img/favicon.ico">
|
|
<title>Concept of the Extractor - NewPipe Documentation</title>
|
|
<!-- local fonts -->
|
|
<link rel="stylesheet" href="../css/local_fonts.css" type="text/css" />
|
|
|
|
<link rel="stylesheet" href="../css/theme.css" type="text/css" />
|
|
<link rel="stylesheet" href="../css/theme_extra.css" type="text/css" />
|
|
<!-- local code syntax highlighting -->
|
|
<link rel="stylesheet" href="../css/github.min.css" type="text/css" />
|
|
<link rel="stylesheet" href="../css/highlight.css" type="text/css" />
|
|
|
|
<script>
|
|
// Current page data
|
|
var mkdocs_page_name = "Concept of the Extractor";
|
|
var mkdocs_page_input_path = "01_Concept_of_the_extractor.md";
|
|
var mkdocs_page_url = null;
|
|
</script>
|
|
|
|
<script src="../js/jquery-2.1.1.min.js" defer></script>
|
|
<script src="../js/modernizr-2.8.3.min.js" defer></script>
|
|
<script src="../js/highlight.min.js"></script>
|
|
<script>hljs.initHighlightingOnLoad();</script>
|
|
|
|
</head>
|
|
|
|
<body class="wy-body-for-nav" role="document">
|
|
|
|
<div class="wy-grid-for-nav">
|
|
|
|
|
|
<nav data-toggle="wy-nav-shift" class="wy-nav-side stickynav">
|
|
<div class="wy-side-nav-search">
|
|
<a href=".." class="icon icon-home"> NewPipe Documentation</a>
|
|
<div role="search">
|
|
<form id ="rtd-search-form" class="wy-form" action="../search.html" method="get">
|
|
<input type="text" name="q" placeholder="Search docs" title="Type search term here" />
|
|
</form>
|
|
</div>
|
|
</div>
|
|
|
|
<div class="wy-menu wy-menu-vertical" data-spy="affix" role="navigation" aria-label="main navigation">
|
|
<ul class="current">
|
|
|
|
|
|
<li class="toctree-l1">
|
|
|
|
<a class="" href="..">Welcome to the NewPipe Documentation.</a>
|
|
</li>
|
|
|
|
<li class="toctree-l1">
|
|
|
|
<a class="" href="../00_Prepare_everything/">Prepare everything</a>
|
|
</li>
|
|
|
|
<li class="toctree-l1 current">
|
|
|
|
<a class="current" href="./">Concept of the Extractor</a>
|
|
<ul class="subnav">
|
|
|
|
<li class="toctree-l2"><a href="#concept-of-the-extractor">Concept of the Extractor</a></li>
|
|
|
|
<ul>
|
|
|
|
<li><a class="toctree-l3" href="#collectorextractor-pattern">Collector/Extractor pattern</a></li>
|
|
|
|
<li><a class="toctree-l3" href="#collectorextractor-pattern-for-lists">Collector/Extractor pattern for lists</a></li>
|
|
|
|
<li><a class="toctree-l3" href="#infoitems-encapsulated-in-pages">InfoItems encapsulated in pages</a></li>
|
|
|
|
</ul>
|
|
|
|
|
|
</ul>
|
|
</li>
|
|
|
|
<li class="toctree-l1">
|
|
|
|
<a class="" href="../02_Concept_of_LinkHandler/">Concept of LinkHandler</a>
|
|
</li>
|
|
|
|
<li class="toctree-l1">
|
|
|
|
<a class="" href="../03_Implement_a_service/">Implement a service</a>
|
|
</li>
|
|
|
|
<li class="toctree-l1">
|
|
|
|
<a class="" href="../04_Run_changes_in_App/">Run the changes in the App</a>
|
|
</li>
|
|
|
|
<li class="toctree-l1">
|
|
|
|
<a class="" href="../05_releasing/">Releasing a new NewPipe version</a>
|
|
</li>
|
|
|
|
<li class="toctree-l1">
|
|
|
|
<a class="" href="../06_documentation/">Documentation</a>
|
|
</li>
|
|
|
|
</ul>
|
|
</div>
|
|
|
|
</nav>
|
|
|
|
<section data-toggle="wy-nav-shift" class="wy-nav-content-wrap">
|
|
|
|
|
|
<nav class="wy-nav-top" role="navigation" aria-label="top navigation">
|
|
<i data-toggle="wy-nav-top" class="fa fa-bars"></i>
|
|
<a href="..">NewPipe Documentation</a>
|
|
</nav>
|
|
|
|
|
|
<div class="wy-nav-content">
|
|
<div class="rst-content">
|
|
<div role="navigation" aria-label="breadcrumbs navigation">
|
|
<ul class="wy-breadcrumbs">
|
|
<li><a href="..">Docs</a> »</li>
|
|
|
|
|
|
|
|
<li>Concept of the Extractor</li>
|
|
<li class="wy-breadcrumbs-aside">
|
|
|
|
</li>
|
|
</ul>
|
|
<hr/>
|
|
</div>
|
|
<div role="main">
|
|
<div class="section">
|
|
|
|
<h1 id="concept-of-the-extractor">Concept of the Extractor</h1>
|
|
<h2 id="collectorextractor-pattern">Collector/Extractor pattern</h2>
|
|
<p>Before we can start coding our own service we need to understand the basic concept of the extractor. There is a pattern
|
|
you will find all over the code. It is called the <strong>extractor/collector</strong> pattern. The idea behind it is that
|
|
the <a href="https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/Extractor.html">extractor</a>
|
|
would produce single pieces of data, and the collector would collect it to form usable data for the front end.
|
|
The collector also controls the parsing process, and takes care of error handling. So if the extractor fails at any
|
|
point, the collector will decide whether or not it should continue parsing. This requires the extractor to be made out of
|
|
many small methods. One method for every data field the collector wants to have. The collectors are provided by NewPipe.
|
|
You need to take care of the extractors.</p>
|
|
<h3 id="usage-in-the-front-end">Usage in the front end</h3>
|
|
<p>So typical call for retrieving data from a website would look like this:</p>
|
|
<pre><code class="java">Info info;
|
|
try {
|
|
// Create a new Extractor with a given context provided as parameter.
|
|
Extractor extractor = new Extractor(some_meta_info);
|
|
// Retrieves the data form extractor and builds info package.
|
|
info = Info.getInfo(extractor);
|
|
} catch(Exception e) {
|
|
// handle errors when collector decided to break up extraction
|
|
}
|
|
</code></pre>
|
|
|
|
<h3 id="typical-implementation-of-a-single-data-extractor">Typical implementation of a single data extractor</h3>
|
|
<p>The typical implementation of a single data extractor on the other hand would look like this:</p>
|
|
<pre><code class="java">class MyExtractor extends FutureExtractor {
|
|
|
|
public MyExtractor(RequiredInfo requiredInfo, ForExtraction forExtraction) {
|
|
super(requiredInfo, forExtraction);
|
|
|
|
...
|
|
}
|
|
|
|
@Override
|
|
public void fetch() {
|
|
// Actually fetch the page data here
|
|
}
|
|
|
|
@Override
|
|
public String someDataFiled()
|
|
throws ExtractionException { //The exception needs to be thrown if someting failed
|
|
// get piece of information and return it
|
|
}
|
|
|
|
... // More datafields
|
|
}
|
|
</code></pre>
|
|
|
|
<h2 id="collectorextractor-pattern-for-lists">Collector/Extractor pattern for lists</h2>
|
|
<p>Sometimes information can be represented as a list. In NewPipe a list is represented by a
|
|
<a href="https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/InfoItemsCollector.html">InfoItemsCollector</a>.
|
|
A InfoItemCollector will collect and assemble a list of <a href="https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/InfoItem.html">InfoItem</a>.
|
|
For each item that should be extracted a new Extractor must be created, and given to the InfoItemCollector via <a href="https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/InfoItemsCollector.html#commit-E-">commit()</a>.</p>
|
|
<p><img alt="InfoItemsCollector_objectdiagram.svg" src="../img/InfoItemsCollector_objectdiagram.svg" /></p>
|
|
<p>If you are implementing a list for your service you need to extend InfoItem containing the extracted information,
|
|
and implement an <a href="https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/Extractor.html">InfoItemExtractor</a>
|
|
that will return the data of one InfoItem.</p>
|
|
<p>A common Implementation would look like this:</p>
|
|
<pre><code>private MyInfoItemCollector collectInfoItemsFromElement(Element e) {
|
|
MyInfoItemCollector collector = new MyInfoItemCollector(getServiceId());
|
|
|
|
for(final Element li : element.children()) {
|
|
collector.commit(new InfoItemExtractor() {
|
|
@Override
|
|
public String getName() throws ParsingException {
|
|
...
|
|
}
|
|
|
|
@Override
|
|
public String getUrl() throws ParsingException {
|
|
...
|
|
}
|
|
|
|
...
|
|
}
|
|
return collector;
|
|
}
|
|
|
|
</code></pre>
|
|
|
|
<h2 id="infoitems-encapsulated-in-pages">InfoItems encapsulated in pages</h2>
|
|
<p>When a streaming site shows a list of items it usually offers some additional information about that list, like it's title, a thumbnail,
|
|
or its creator. Such info can be called <strong>list header</strong>.</p>
|
|
<p>When a website shows a long list of items it usually does not load the whole list, but only a part of it. In order to get more items you may have to click on a next page button, or scroll down. </p>
|
|
<p>This is why a list in NewPipe lists are chopped down into smaller lists called <a href="https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/ListExtractor.InfoItemsPage.html">InfoItemsPage</a>s. Each page has its own URL, and needs to be extracted separately.</p>
|
|
<p>Additional metainformation about the list such as its title a thumbnail
|
|
or its creator, and extracting multiple pages can be handled by a
|
|
<a href="https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/ListExtractor.html">ListExtractor</a>,
|
|
and it's <a href="https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/ListExtractor.InfoItemsPage.html">ListExtractor.InfoItemsPage</a>.</p>
|
|
<p>For extracting list header information it behaves like a regular extractor. For handling <code>InfoItemsPages</code> it adds methods
|
|
such as:</p>
|
|
<ul>
|
|
<li><a href="https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/ListExtractor.html#getInitialPage--">getInitialPage()</a>
|
|
which will return the first page of InfoItems.</li>
|
|
<li><a href="https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/ListExtractor.html#getNextPageUrl--">getNextPageUrl()</a>
|
|
If a second Page of InfoItems is available this will return the URL pointing to them.</li>
|
|
<li><a href="https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/ListExtractor.html#getPage-java.lang.String-">getPage()</a>
|
|
returns a ListExtractor.InfoItemsPage by its URL which was retrieved by the <code>getNextPageUrl()</code> method of the previous page.</li>
|
|
</ul>
|
|
<p>The reason why the first page is handled special is because many Websites such as YouTube will load the first page of
|
|
items like a regular webpage, but all the others as an AJAX request.</p>
|
|
|
|
</div>
|
|
</div>
|
|
<footer>
|
|
|
|
<div class="rst-footer-buttons" role="navigation" aria-label="footer navigation">
|
|
|
|
<a href="../02_Concept_of_LinkHandler/" class="btn btn-neutral float-right" title="Concept of LinkHandler">Next <span class="icon icon-circle-arrow-right"></span></a>
|
|
|
|
|
|
<a href="../00_Prepare_everything/" class="btn btn-neutral" title="Prepare everything"><span class="icon icon-circle-arrow-left"></span> Previous</a>
|
|
|
|
</div>
|
|
|
|
|
|
<hr/>
|
|
|
|
<div role="contentinfo">
|
|
<!-- Copyright etc -->
|
|
|
|
</div>
|
|
|
|
Built with <a href="http://www.mkdocs.org">MkDocs</a> using a <a href="https://github.com/snide/sphinx_rtd_theme">theme</a> provided by <a href="https://readthedocs.org">Read the Docs</a>.
|
|
</footer>
|
|
|
|
</div>
|
|
</div>
|
|
|
|
</section>
|
|
|
|
</div>
|
|
|
|
<div class="rst-versions" role="note" style="cursor: pointer">
|
|
<span class="rst-current-version" data-toggle="rst-current-version">
|
|
|
|
|
|
<span><a href="../00_Prepare_everything/" style="color: #fcfcfc;">« Previous</a></span>
|
|
|
|
|
|
<span style="margin-left: 15px"><a href="../02_Concept_of_LinkHandler/" style="color: #fcfcfc">Next »</a></span>
|
|
|
|
</span>
|
|
</div>
|
|
<script>var base_url = '..';</script>
|
|
<script src="../js/theme.js" defer></script>
|
|
<script src="../search/main.js" defer></script>
|
|
|
|
</body>
|
|
</html>
|