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<!DOCTYPE html>
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<title>Injecting Objects by Using Producer Methods</title>
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<b>Java Platform, Enterprise Edition (Java EE) 8</b><br />
<b>The Java EE Tutorial</b>
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<p><a id="GJDID"></a><a id="injecting-objects-by-using-producer-methods"></a></p>
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<div class="sect1">
<h2 id="_injecting_objects_by_using_producer_methods">Injecting Objects by Using Producer Methods</h2>
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<div class="paragraph">
<p>Producer methods provide a way to inject objects that are not beans,
objects whose values may vary at runtime, and objects that require
custom initialization. For example, if you want to initialize a numeric
value defined by a qualifier named <code>@MaxNumber</code>, then you can define the
value in a managed bean and then define a producer method,
<code>getMaxNumber</code>, for it:</p>
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<pre class="prettyprint highlight"><code class="language-oac_no_warn" data-lang="oac_no_warn">private int maxNumber = 100;
...
@Produces @MaxNumber int getMaxNumber() {
return maxNumber;
}</code></pre>
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<p>When you inject the object in another managed bean, the container
automatically invokes the producer method, initializing the value to
100:</p>
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<div class="content">
<pre class="prettyprint highlight"><code class="language-oac_no_warn" data-lang="oac_no_warn">@Inject @MaxNumber private int maxNumber;</code></pre>
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<p>If the value can vary at runtime, then the process is slightly different. For
example, the following code defines a producer method that generates a
random number defined by a qualifier called <code>@Random</code>:</p>
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<div class="listingblock">
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<pre class="prettyprint highlight"><code class="language-oac_no_warn" data-lang="oac_no_warn">private java.util.Random random =
new java.util.Random( System.currentTimeMillis() );
java.util.Random getRandom() {
return random;
}
@Produces @Random int next() {
return getRandom().nextInt(maxNumber);
}</code></pre>
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<p>When you inject this object in another managed bean, you declare a
contextual instance of the object:</p>
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<pre class="prettyprint highlight"><code class="language-oac_no_warn" data-lang="oac_no_warn">@Inject @Random Instance<Integer> randomInt;</code></pre>
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<p>You then call the <code>get</code> method of the <code>Instance</code>:</p>
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<pre class="prettyprint highlight"><code class="language-oac_no_warn" data-lang="oac_no_warn">this.number = randomInt.get();</code></pre>
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