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Reinier Zwitserloot
84 lines
4.7 KiB
HTML
84 lines
4.7 KiB
HTML
<!DOCTYPE html>
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<html><head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<link rel="stylesheet" type="text/css" href="../logi/reset.css" />
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<link rel="stylesheet" type="text/css" href="features.css" />
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<link rel="shortcut icon" href="../favicon.ico" type="image/x-icon" />
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<meta name="description" content="Spice up your java" />
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<title>@NonNull</title>
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</head><body><div id="pepper">
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<div class="minimumHeight"></div>
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<div class="meat">
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<div class="header"><a href="../index.html">Project Lombok</a></div>
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<h1>@NonNull</h1>
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<div class="byline">or: How I learned to stop worrying and love the NullPointerException.</div>
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<div class="overview">
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<h3>Overview</h3>
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<p>
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<em>NEW in Lombok 0.11.10: </em>You can use <code>@NonNull</code> on the parameter of a method or constructor to have lombok generate a null-check statement for you.
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</p><p>
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Lombok has always treated any annotation named <code>@NonNull</code> on a field as a signal to generate a null-check if lombok generates an entire method or constructor for you, via
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for example <a href="Data.html"><code>@Data</code></a>. Now, however, using lombok's own <code>@lombok.NonNull</code> on a parameter results in the insertion of just the null-check
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statement inside your own method or constructor.
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</p><p>
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The null-check looks like <code>if (param == null) throw new NullPointerException("param");</code> and will be inserted at the very top of your method. For constructors, the null-check
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will be inserted immediately following any explicit <code>this()</code> or <code>super()</code> calls.
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</p><p>
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If a null-check is already present at the top, no additional null-check will be generated.
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</p>
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</div>
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<div class="snippets">
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<div class="pre">
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<h3>With Lombok</h3>
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<div class="snippet">@HTML_PRE@</div>
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</div>
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<div class="sep"></div>
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<div class="post">
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<h3>Vanilla Java</h3>
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<div class="snippet">@HTML_POST@</div>
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</div>
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</div>
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<div style="clear: left;"></div>
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<div class="overview confKeys">
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<h3>Supported configuration keys:</h3>
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<dl>
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<dt><code>lombok.nonNull.exceptionType</code> = [<code>NullPointerException</code> | <code>IllegalArgumentException</code>] (default: <code>NullPointerException</code>).
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<dd>When lombok generates a null-check <code>if</code> statement, by default, a <code>java.lang.NullPointerException</code> will be thrown with the field name as the exception message.
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However, you can use <code>IllegalArgumentException</code> in this configuration key to have lombok throw that exception, with '<em>fieldName</em> is null' as exception message.</dd>
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<dt><code>lombok.nonNull.flagUsage</code> = [<code>warning</code> | <code>error</code>] (default: not set)</dt>
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<dd>Lombok will flag any usage of <code>@NonNull</code> as a warning or error if configured.</dd>
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</dl>
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</div>
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<div class="overview">
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<h3>Small print</h3><div class="smallprint">
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<p>
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Lombok's detection scheme for already existing null-checks consists of scanning for if statements that look just like lombok's own. Any 'throws' statement as
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the 'then' part of the if statement, whether in braces or not, counts. The conditional of the if statement <em>must</em> look exactly like <code>PARAMNAME == null</code>.
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The first statement in your method that is not such a null-check stops the process of inspecting for null-checks.
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</p><p>
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While <code>@Data</code> and other method-generating lombok annotations will trigger on any annotation named <code>@NonNull</code> regardless of casing or package name,
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this feature only triggers on lombok's own <code>@NonNull</code> annotation from the <code>lombok</code> package.
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</p><p>
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A <code>@NonNull</code> on a primitive parameter results in a warning. No null-check will be generated.
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</p>
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</div>
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</div>
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<div class="footer">
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<a href="index.html">Back to features</a> | <a href="val.html">Previous feature (val)</a> | <a href="Cleanup.html">Next feature (@Cleanup)</a><br />
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<a href="../credits.html" class="creditsLink">credits</a> | <span class="copyright">Copyright © 2009-2015 The Project Lombok Authors, licensed under the <a href="http://www.opensource.org/licenses/mit-license.php">MIT license</a>.</span>
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