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<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/0.20.4-incubating/guides-effectively-once-java-topologies"><span class="arrow-prev">← </span><span>Effectively Once Java Topologies</span></a><a class="docs-next button" href="/docs/0.20.4-incubating/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, 
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