AnnotationPresentCheck.qhelp

<!DOCTYPE qhelp PUBLIC
  "-//Semmle//qhelp//EN"
  "qhelp.dtd">
<qhelp>


<overview>
<p>To be able to use the <code>isAnnotationPresent</code> method on an <code>AnnotatedElement</code> at runtime,
an annotation must be explicitly annotated with a <code>RUNTIME</code> retention policy.
Otherwise, the annotation is not retained at runtime and cannot be observed using reflection.
</p>

</overview>
<recommendation>

<p>Explicitly annotate annotations with a <code>RUNTIME</code> retention policy
if you want to observe their presence using <code>AnnotatedElement.isAnnotationPresent</code>
at runtime.
</p>

</recommendation>
<example>

<p>In the following example, the call to <code>isAnnotationPresent</code> returns <code>false</code>
because the annotation cannot be observed using reflection.</p>

<sample src="AnnotationPresentCheck.java" />

<p>To correct this, the annotation is annotated with a <code>RUNTIME</code> retention policy.</p>

<sample src="AnnotationPresentCheckFix.java" />

</example>
<references>


<li>
  Java API Specification:
  <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/annotation/Retention.html">Annotation Type Retention</a>,
  <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/annotation/RetentionPolicy.html#RUNTIME">RetentionPolicy.RUNTIME</a>,
  <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/reflect/AnnotatedElement.html#isAnnotationPresent(java.lang.Class)">AnnotatedElement.isAnnotationPresent()</a>.
</li>


</references>
</qhelp>