Google Git
Sign in
apache / incubator-heron / refs/heads/asf-site / . / content / docs / guides-data-model / index.html
blob: ac46a3287f39fb231dd6f20393f81703e5e99e3b [file] [log] [blame]
<!DOCTYPE html><html lang="en"><head><meta charSet="utf-8"/><meta http-equiv="X-UA-Compatible" content="IE=edge"/><title>Heron Data Model · Apache Heron</title><meta name="viewport" content="width=device-width"/><meta name="generator" content="Docusaurus"/><meta name="description" content="&lt;!--"/><meta name="docsearch:version" content="0.20.5-incubating"/><meta name="docsearch:language" content="en"/><meta property="og:title" content="Heron Data Model · Apache Heron"/><meta property="og:type" content="website"/><meta property="og:url" content="https://heron.apache.org/"/><meta property="og:description" content="&lt;!--"/><meta property="og:image" content="https://heron.apache.org/img/undraw_online.svg"/><meta name="twitter:card" content="summary"/><meta name="twitter:image" content="https://heron.apache.org/img/undraw_tweetstorm.svg"/><link rel="shortcut icon" href="/img/favicon-32x32.png"/><link rel="stylesheet" href="//cdnjs.cloudflare.com/ajax/libs/highlight.js/9.12.0/styles/default.min.css"/><link rel="alternate" type="application/atom+xml" href="https://heron.apache.org/blog/atom.xml" title="Apache Heron Blog ATOM Feed"/><link rel="alternate" type="application/rss+xml" href="https://heron.apache.org/blog/feed.xml" title="Apache Heron Blog RSS Feed"/><script>
(function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
(i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
})(window,document,'script','https://www.google-analytics.com/analytics.js','ga');
ga('create', 'UA-198017384-1', 'auto');
ga('send', 'pageview');
</script><script type="text/javascript" src="https://buttons.github.io/buttons.js"></script><script type="text/javascript" src="/js/custom.js"></script><script type="text/javascript" src="/js/fix-location.js"></script><link rel="stylesheet" href="/css/main.css"/><script src="/js/codetabs.js"></script></head><body class="sideNavVisible separateOnPageNav"><div class="fixedHeaderContainer"><div class="headerWrapper wrapper"><header><a href="/"><img class="logo" src="/img/HeronTextLogo-small.png" alt="Apache Heron"/><h2 class="headerTitleWithLogo">Apache Heron</h2></a><a href="/versions"><h3>0.20.5-incubating</h3></a><div class="navigationWrapper navigationSlider"><nav class="slidingNav"><ul class="nav-site nav-site-internal"><li class=""><a href="/api/java" target="_self">Javadocs</a></li><li class=""><a href="/api/python" target="_self">Pydocs</a></li><li class="siteNavGroupActive"><a href="/docs/getting-started-local-single-node" target="_self">Docs</a></li><li class=""><a href="/download" target="_self">Downloads</a></li><li class=""><a href="#community" target="_self">Community</a></li><li class=""><a href="/blog/" target="_self">Blog</a></li><li class=""><a href="#apache" target="_self">Apache</a></li></ul></nav></div></header></div></div><div class="navPusher"><div class="docMainWrapper wrapper"><div class="container docsNavContainer" id="docsNav"><nav class="toc"><div class="toggleNav"><section class="navWrapper wrapper"><div class="navBreadcrumb wrapper"><div class="navToggle" id="navToggler"><div class="hamburger-menu"><div class="line1"></div><div class="line2"></div><div class="line3"></div></div></div><h2><i>›</i><span>Guides</span></h2><div class="tocToggler" id="tocToggler"><i class="icon-toc"></i></div></div><div class="navGroups"><div class="navGroup"><h3 class="navGroupCategoryTitle">Getting Started</h3><ul class=""><li class="navListItem"><a class="navItem" href="/docs/getting-started-local-single-node">Local (Single Node)</a></li><li class="navListItem"><a class="navItem" href="/docs/getting-started-migrate-storm-topologies">Migrate Storm Topologies</a></li><li class="navListItem"><a class="navItem" href="/docs/getting-started-docker">Heron &amp; Docker</a></li><li class="navListItem"><a class="navItem" href="/docs/getting-started-troubleshooting-guide">Troubleshooting Guide</a></li></ul></div><div class="navGroup"><h3 class="navGroupCategoryTitle">Deployment</h3><ul class=""><li class="navListItem"><a class="navItem" href="/docs/deployment-overview">Deployment Overiew</a></li><li class="navListItem"><a class="navItem" href="/docs/deployment-configuration">Configuration</a></li><li class="navListItem"><a class="navItem" href="/docs/deployment-api-server">The Heron API Server</a></li></ul></div><div class="navGroup"><h3 class="navGroupCategoryTitle">Topology Development APIs</h3><ul class=""><li class="navListItem"><a class="navItem" href="/docs/topology-development-streamlet-api">The Heron Streamlet API for Java</a></li><li class="navListItem"><a class="navItem" href="/docs/topology-development-eco-api">The ECO API for Java</a></li><li class="navListItem"><a class="navItem" href="/docs/topology-development-topology-api-java">The Heron Topology API for Java</a></li><li class="navListItem"><a class="navItem" href="/docs/topology-development-topology-api-python">The Heron Topology API for Python</a></li><li class="navListItem"><a class="navItem" href="/docs/topology-development-streamlet-scala">The Heron Streamlet API for Scala</a></li></ul></div><div class="navGroup"><h3 class="navGroupCategoryTitle">Client API Docs</h3><ul class=""><li class="navListItem"><a class="navItem" href="/docs/client-api-docs-overview">Client API Docs</a></li></ul></div><div class="navGroup"><h3 class="navGroupCategoryTitle">Guides</h3><ul class=""><li class="navListItem"><a class="navItem" href="/docs/guides-effectively-once-java-topologies">Effectively Once Java Topologies</a></li><li class="navListItem navListItemActive"><a class="navItem" href="/docs/guides-data-model">Heron Data Model</a></li><li class="navListItem"><a class="navItem" href="/docs/guides-tuple-serialization">Tuple Serialization</a></li><li class="navListItem"><a class="navItem" href="/docs/guides-ui-guide">Heron UI Guide</a></li><li class="navListItem"><a class="navItem" href="/docs/guides-topology-tuning">Topology Tuning Guide</a></li><li class="navListItem"><a class="navItem" href="/docs/guides-packing-algorithms">Packing Algorithms</a></li><li class="navListItem"><a class="navItem" href="/docs/guides-simulator-mode">Simulator Mode</a></li><li class="navListItem"><a class="navItem" href="/docs/guides-troubeshooting-guide">Topology Troubleshooting Guide</a></li></ul></div><div class="navGroup"><h3 class="navGroupCategoryTitle">Heron Concepts</h3><ul class=""><li class="navListItem"><a class="navItem" href="/docs/heron-design-goals">Heron Design Goals</a></li><li class="navListItem"><a class="navItem" href="/docs/heron-topology-concepts">Heron Topologies</a></li><li class="navListItem"><a class="navItem" href="/docs/heron-streamlet-concepts">Heron Streamlets</a></li><li class="navListItem"><a class="navItem" href="/docs/heron-architecture">Heron Architecture</a></li><li class="navListItem"><a class="navItem" href="/docs/heron-delivery-semantics">Heron Delivery Semantics</a></li></ul></div><div class="navGroup"><h3 class="navGroupCategoryTitle">State Managers</h3><ul class=""><li class="navListItem"><a class="navItem" href="/docs/state-managers-zookeeper">Zookeeper</a></li><li class="navListItem"><a class="navItem" href="/docs/state-managers-local-fs">Local File System</a></li></ul></div><div class="navGroup"><h3 class="navGroupCategoryTitle">Uploaders</h3><ul class=""><li class="navListItem"><a class="navItem" href="/docs/uploaders-local-fs">Local File System</a></li><li class="navListItem"><a class="navItem" href="/docs/uploaders-hdfs">HDFS</a></li><li class="navListItem"><a class="navItem" href="/docs/uploaders-http">HTTP</a></li><li class="navListItem"><a class="navItem" href="/docs/uploaders-amazon-s3">Amazon S3</a></li><li class="navListItem"><a class="navItem" href="/docs/uploaders-scp">Secure Copy (SCP)</a></li></ul></div><div class="navGroup"><h3 class="navGroupCategoryTitle">Schedulers</h3><ul class=""><li class="navListItem"><a class="navItem" href="/docs/schedulers-k8s-by-hand">Kubernetes by hand</a></li><li class="navListItem"><a class="navItem" href="/docs/schedulers-k8s-with-helm">Kubernetes with Helm</a></li><li class="navListItem"><a class="navItem" href="/docs/schedulers-k8s-execution-environment">Kubernetes Environment Customization</a></li><li class="navListItem"><a class="navItem" href="/docs/schedulers-aurora-cluster">Aurora Cluster</a></li><li class="navListItem"><a class="navItem" href="/docs/schedulers-aurora-local">Aurora Locally</a></li><li class="navListItem"><a class="navItem" href="/docs/schedulers-local">Local Cluster</a></li><li class="navListItem"><a class="navItem" href="/docs/schedulers-nomad">Nomad</a></li><li class="navListItem"><a class="navItem" href="/docs/schedulers-mesos-local-mac">Mesos Cluster Locally</a></li><li class="navListItem"><a class="navItem" href="/docs/schedulers-slurm">Slurm Cluster</a></li><li class="navListItem"><a class="navItem" href="/docs/schedulers-yarn">YARN Cluster</a></li></ul></div><div class="navGroup"><h3 class="navGroupCategoryTitle">Cluster Configuration</h3><ul class=""><li class="navListItem"><a class="navItem" href="/docs/cluster-config-overview">Cluster Config Overview</a></li><li class="navListItem"><a class="navItem" href="/docs/cluster-config-system-level">System Level Configuration</a></li><li class="navListItem"><a class="navItem" href="/docs/cluster-config-instance">Heron Instance</a></li><li class="navListItem"><a class="navItem" href="/docs/cluster-config-metrics">Metrics Manager</a></li><li class="navListItem"><a class="navItem" href="/docs/cluster-config-stream">Stream Manager</a></li><li class="navListItem"><a class="navItem" href="/docs/cluster-config-tmanager">Topology Manager</a></li></ul></div><div class="navGroup"><h3 class="navGroupCategoryTitle">Observability</h3><ul class=""><li class="navListItem"><a class="navItem" href="/docs/observability-prometheus">Prometheus</a></li><li class="navListItem"><a class="navItem" href="/docs/observability-graphite">Graphite</a></li><li class="navListItem"><a class="navItem" href="/docs/observability-scribe">Scribe</a></li></ul></div><div class="navGroup"><h3 class="navGroupCategoryTitle">User Manuals</h3><ul class=""><li class="navListItem"><a class="navItem" href="/docs/user-manuals-heron-cli">Heron Client</a></li><li class="navListItem"><a class="navItem" href="/docs/user-manuals-heron-explorer">Heron Explorer</a></li><li class="navListItem"><a class="navItem" href="/docs/user-manuals-tracker-rest">Heron Tracker REST API</a></li><li class="navListItem"><a class="navItem" href="/docs/user-manuals-heron-tracker-runbook">Heron Tracker Runbook</a></li><li class="navListItem"><a class="navItem" href="/docs/user-manuals-heron-ui-runbook">Heron UI Runbook</a></li><li class="navListItem"><a class="navItem" href="/docs/user-manuals-heron-shell">Heron Shell</a></li></ul></div><div class="navGroup"><h3 class="navGroupCategoryTitle">Compiling</h3><ul class=""><li class="navListItem"><a class="navItem" href="/docs/compiling-overview">Compiling Overview</a></li><li class="navListItem"><a class="navItem" href="/docs/compiling-linux">Compiling on Linux</a></li><li class="navListItem"><a class="navItem" href="/docs/compiling-osx">Compiling on OS X</a></li><li class="navListItem"><a class="navItem" href="/docs/compiling-docker">Compiling With Docker</a></li><li class="navListItem"><a class="navItem" href="/docs/compiling-running-tests">Running Tests</a></li><li class="navListItem"><a class="navItem" href="/docs/compiling-code-organization">Code Organization</a></li></ul></div><div class="navGroup"><h3 class="navGroupCategoryTitle">Extending Heron</h3><ul class=""><li class="navListItem"><a class="navItem" href="/docs/extending-heron-scheduler">Custom Scheduler</a></li><li class="navListItem"><a class="navItem" href="/docs/extending-heron-metric-sink">Custom Metrics Sink</a></li></ul></div><div class="navGroup"><h3 class="navGroupCategoryTitle">Heron Resources</h3><ul class=""><li class="navListItem"><a class="navItem" href="/docs/heron-resources-resources">Heron Resources</a></li></ul></div></div></section></div><script>
var coll = document.getElementsByClassName('collapsible');
var checkActiveCategory = true;
for (var i = 0; i < coll.length; i++) {
var links = coll[i].nextElementSibling.getElementsByTagName('*');
if (checkActiveCategory){
for (var j = 0; j < links.length; j++) {
if (links[j].classList.contains('navListItemActive')){
coll[i].nextElementSibling.classList.toggle('hide');
coll[i].childNodes[1].classList.toggle('rotate');
checkActiveCategory = false;
break;
}
}
}
coll[i].addEventListener('click', function() {
var arrow = this.childNodes[1];
arrow.classList.toggle('rotate');
var content = this.nextElementSibling;
content.classList.toggle('hide');
});
}
document.addEventListener('DOMContentLoaded', function() {
createToggler('#navToggler', '#docsNav', 'docsSliderActive');
createToggler('#tocToggler', 'body', 'tocActive');
var headings = document.querySelector('.toc-headings');
headings && headings.addEventListener('click', function(event) {
var el = event.target;
while(el !== headings){
if (el.tagName === 'A') {
document.body.classList.remove('tocActive');
break;
} else{
el = el.parentNode;
}
}
}, false);
function createToggler(togglerSelector, targetSelector, className) {
var toggler = document.querySelector(togglerSelector);
var target = document.querySelector(targetSelector);
if (!toggler) {
return;
}
toggler.onclick = function(event) {
event.preventDefault();
target.classList.toggle(className);
};
}
});
</script></nav></div><div class="container mainContainer"><div class="wrapper"><div class="post"><header class="postHeader"><h1 class="postHeaderTitle">Heron Data Model</h1></header><article><div><span><!--
Licensed to the Apache Software Foundation (ASF) under one
or more contributor license agreements. See the NOTICE file
distributed with this work for additional information
regarding copyright ownership. The ASF licenses this file
to you under the Apache License, Version 2.0 (the
"License"); you may not use this file except in compliance
with the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing,
software distributed under the License is distributed on an
"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
KIND, either express or implied. See the License for the
specific language governing permissions and limitations
under the License.
-->
<p>Tuple is Heron's core data type. All
data that is fed into a Heron topology via
<a href="../../concepts/topologies#spouts">spouts</a> and then processed by
<a href="../../concepts/topologies#bolts">bolts</a> consists of tuples.</p>
<p>Heron has a <a href="/api/org/apache/heron/api/tuple/Tuple.html"><code>Tuple</code></a>
interface for working with tuples. Heron <code>Tuple</code>s can hold values of any type;
values are accessible either by providing an index or a field name.</p>
<h2><a class="anchor" aria-hidden="true" id="using-tuples"></a><a href="#using-tuples" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Using Tuples</h2>
<p>Heron's <code>Tuple</code> interface contains the methods listed in the <a href="/api/org/apache/heron/api/tuple/Tuple.html">Javadoc
definition</a>.</p>
<h3><a class="anchor" aria-hidden="true" id="accessing-primitive-types-by-index"></a><a href="#accessing-primitive-types-by-index" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Accessing Primitive Types By Index</h3>
<p>Heron <code>Tuple</code>s support a wide variety of primitive Java types, including
strings, Booleans, byte arrays, and more.
<a href="/api/org/apache/heron/api/tuple/Tuple.html#getString-int-"><code>getString</code></a>
method, for example, takes an integer index and returns either a string or
<code>null</code> if no string value is present at that index. Analogous methods can be
found in the Javadoc.</p>
<h3><a class="anchor" aria-hidden="true" id="accessing-primitive-types-by-field"></a><a href="#accessing-primitive-types-by-field" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Accessing Primitive Types By Field</h3>
<p>In addition to being accessible via index, values stored in Heron tuples are
accessible via field name as well. The
<a href="/api/org/apache/heron/api/tuple/Tuple.html#getStringByField-java.lang.String-"><code>getStringByField</code></a>
method, for example, takes a field name string and returns either a string or
<code>null</code> if no string value is present for that field name. Analogous methods can
be found in the Javadoc.</p>
<h3><a class="anchor" aria-hidden="true" id="using-non-primitive-types"></a><a href="#using-non-primitive-types" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Using Non-primitive Types</h3>
<p>In addition to primitive types, you can access any value in a Heron <code>Tuple</code> as a
Java <code>Object</code>. As for primitive types, you can access <code>Object</code>s on the basis of
an index or a field name. The following methods return either an <code>Object</code> or
<code>null</code> if no object is present:</p>
<ul>
<li><a href="/api/org/apache/heron/api/tuple/Tuple.html#getValue-int-"><code>getValue</code></a></li>
<li><a href="/api/org/apache/heron/api/tuple/Tuple.html#getValueByField-java.lang.String-"><code>getValueByField</code></a></li>
</ul>
<p>You can also retrieve all objects contained in a Heron <code>Tuple</code> as a Java
<a href="https://docs.oracle.com/javase/8/docs/api/java/util/List.html">List</a> using the
<a href="/api/org/apache/heron/api/tuple/Tuple.html#getValues--"><code>getValues</code></a>
method.</p>
<h3><a class="anchor" aria-hidden="true" id="user-defined-types"></a><a href="#user-defined-types" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>User-defined Types</h3>
<p>You use Heron tuples in conjunction with more complex, user-defined types using
<a href="http://www.studytonight.com/java/type-casting-in-java">type casting</a>, provided
that you've created and registered a <a href="../serialization">custom serializer</a> for the type.
Here's an example (which assumes that a serializer for the type
<code>Tweet</code> has been created and registered):</p>
<pre><code class="hljs css language-java"><span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">execute</span><span class="hljs-params">(Tuple input)</span> </span>{
<span class="hljs-comment">// The following return null if no value is present or throws a</span>
<span class="hljs-comment">// ClassCastException if type casting fails:</span>
Tweet tweet = (Tweet) input.getValue(<span class="hljs-number">0</span>);
List&lt;Tweet&gt; allTweets = input.getValues();
}
</code></pre>
<p>More info on custom serialization can be found in <a href="guides-tuple-serialization">Creating Custom Tuple
Serializers</a>.</p>
<h3><a class="anchor" aria-hidden="true" id="fields"></a><a href="#fields" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Fields</h3>
<p>The <code>getFields</code> method returns a
<a href="http://heronproject.github.io/topology-api/org/apache/heron/api/tuple/Fields"><code>Fields</code></a>
object that contains all of the fields in the tuple. More on fields can be found
<a href="#Fields">below</a>.</p>
<h3><a class="anchor" aria-hidden="true" id="other-methods"></a><a href="#other-methods" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Other Methods</h3>
<p>There are additional methods available for determining the size of Heron
<code>Tuple</code>s, extracting contextual information, and more. For a full listing of
methods, see the
<a href="/api/org/apache/heron/api/tuple/Tuple.html">Javadoc</a>.</p>
<h2><a class="anchor" aria-hidden="true" id="fields-1"></a><a href="#fields-1" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Fields</h2>
<p>From the methods in the list above you can see that you can retrieve single
values from a Heron tuple on the basis of their index. You can also retrieve
multiple values using a
<a href="/api/org/apache/heron/api/tuple/Fields.html"><code>Fields</code></a> object,
which can be initialized either using varargs or a list of strings:</p>
<pre><code class="hljs css language-java"><span class="hljs-comment">// Using varargs</span>
Fields fruits = <span class="hljs-keyword">new</span> Fields(<span class="hljs-string">"apple"</span>, <span class="hljs-string">"orange"</span>, <span class="hljs-string">"banana"</span>);
<span class="hljs-comment">// Using a list of strings</span>
List&lt;String&gt; fruitNames = <span class="hljs-keyword">new</span> LinkedList&lt;String&gt;();
fruitNames.add(<span class="hljs-string">"apple"</span>);
<span class="hljs-comment">// Add "orange" and "banana" as well</span>
Fields fruits = <span class="hljs-keyword">new</span> Fields(fruitNames);
</code></pre>
<p>You can then use that object in conjunction with a tuple:</p>
<pre><code class="hljs css language-java"><span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">execute</span><span class="hljs-params">(Tuple input)</span> </span>{
List&lt;Object&gt; values = input.select(fruits);
<span class="hljs-keyword">for</span> (Object value : values) {
System.out.println(value);
}
}
</code></pre>
</span></div></article></div><div class="docs-prevnext"><a class="docs-prev button" href="/docs/guides-effectively-once-java-topologies"><span class="arrow-prev">← </span><span>Effectively Once Java Topologies</span></a><a class="docs-next button" href="/docs/guides-tuple-serialization"><span>Tuple Serialization</span><span class="arrow-next"> →</span></a></div></div></div><nav class="onPageNav"><ul class="toc-headings"><li><a href="#using-tuples">Using Tuples</a><ul class="toc-headings"><li><a href="#accessing-primitive-types-by-index">Accessing Primitive Types By Index</a></li><li><a href="#accessing-primitive-types-by-field">Accessing Primitive Types By Field</a></li><li><a href="#using-non-primitive-types">Using Non-primitive Types</a></li><li><a href="#user-defined-types">User-defined Types</a></li><li><a href="#fields">Fields</a></li><li><a href="#other-methods">Other Methods</a></li></ul></li><li><a href="#fields-1">Fields</a></li></ul></nav></div><footer class="nav-footer" id="footer"><div class="apache-disclaimer">Apache Heron is an effort undergoing incubation at <a target="_blank" href="https://apache.org/">The Apache Software Foundation (ASF)</a> sponsored by the Apache Incubator PMC. Incubation is required of all newly accepted projects until a further review indicates that the infrastructure, communications, and decision making process have stabilized in a manner consistent with other successful ASF projects. While incubation status is not necessarily a reflection of the completeness or stability of the code, it does indicate that the project has yet to be fully endorsed by the ASF.<br/><br/>Apache®, the names of Apache projects, and the feather logo are either <a rel="external" href="https://www.apache.org/foundation/marks/list/">registered trademarks or trademarks</a> of the Apache Software Foundation in the United States and/or other countries.<br/><br/><div class="copyright-box">Copyright © 2023 the Apache Software Foundation, Apache Heron, Heron,
Apache, the Apache feather Logo, and the Apache Heron project logo are either registered
trademarks or trademarks of the Apache Software Foundation.</div></div><div class="apache-links"><a class="item" rel="external" href="https://incubator.apache.org/">Apache Incubator</a><div><a class="item" rel="external" href="https://www.apache.org/">About the ASF</a></div><div><a class="item" rel="external" href="https://www.apache.org/events/current-event">Events</a></div><div><a class="item" rel="external" href="https://www.apache.org/foundation/thanks.html">Thanks</a></div><div><a class="item" rel="external" href="https://www.apache.org/foundation/sponsorship.html">Become a Sponsor</a></div><div><a class="item" rel="external" href="https://www.apache.org/security/">Security</a></div><div><a class="item" rel="external" href="https://www.apache.org/licenses/">License</a></div></div></footer></div><script>window.twttr=(function(d,s, id){var js,fjs=d.getElementsByTagName(s)[0],t=window.twttr||{};if(d.getElementById(id))return t;js=d.createElement(s);js.id=id;js.src='https://platform.twitter.com/widgets.js';fjs.parentNode.insertBefore(js, fjs);t._e = [];t.ready = function(f) {t._e.push(f);};return t;}(document, 'script', 'twitter-wjs'));</script></body></html>