1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
|
<!DOCTYPE html>
<html><head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<link rel="stylesheet" type="text/css" href="../logi/reset.css" />
<link rel="stylesheet" type="text/css" href="features.css" />
<link rel="shortcut icon" href="../favicon.ico" type="image/x-icon" />
<meta name="description" content="Spice up your java" />
<title>val</title>
</head><body><div id="pepper">
<div class="minimumHeight"></div>
<div class="meat">
<div class="header"><a href="../index.html">Project Lombok</a></div>
<h1>@NonNull</h1>
<div class="byline">or: How I learned to stop worrying and love the NullPointerException.</div>
<div class="overview">
<h3>Overview</h3>
<p>
<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.
</p><p>
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
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
statement inside your own method or constructor.
</p><p>
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
will be inserted immediately following any explicit <code>this()</code> or <code>super()</code> calls.
</p><p>
If a null-check is already present at the top, no additional null-check will be generated.
</p>
</div>
<div class="snippets">
<div class="pre">
<h3>With Lombok</h3>
<div class="snippet">@HTML_PRE@</div>
</div>
<div class="sep"></div>
<div class="post">
<h3>Vanilla Java</h3>
<div class="snippet">@HTML_POST@</div>
</div>
</div>
<div style="clear: left;"></div>
<div class="overview confKeys">
<h3>Supported configuration keys:</h3>
<dl>
<dt><code>lombok.nonNull.exceptionType</code> = [<code>fully qualified name of an exception</code>] (default: <code>java.lang.NullPointerException</code>).
<dd>When lombok generates a null-check <code>if</code> statement, an exception is thrown, with the parameter / field name as message. By default, this will be a <code>java.lang.NullPointerException</code>, but you can for example put <code>java.lang.IllegalArgumentException</code> in this configuration key to have lombok throw a different exception.</dd>
<dt><code>lombok.nonNull.flagUsage</code> = [<code>warning</code> | <code>error</code>] (default: not set)</dt>
<dd>Lombok will flag any usage of <code>@NonNull</code> as a warning or error if configured.</dd>
</dl>
</div>
<div class="overview">
<h3>Small print</h3><div class="smallprint">
<p>
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
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>.
The first statement in your method that is not such a null-check stops the process of inspecting for null-checks.
</p><p>
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,
this feature only triggers on lombok's own <code>@NonNull</code> annotation from the <code>lombok</code> package.
</p><p>
A <code>@NonNull</code> on a primitive parameter results in a warning. No null-check will be generated.
</p>
</div>
</div>
<div class="footer">
<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 />
<a href="../credits.html" class="creditsLink">credits</a> | <span class="copyright">Copyright © 2013 The Project Lombok Authors, licensed under the <a href="http://www.opensource.org/licenses/mit-license.php">MIT license</a>.</span>
</div>
<div style="clear: both;"></div>
</div>
</div>
<script type="text/javascript">
var gaJsHost = (("https:" == document.location.protocol) ? "https://ssl." : "http://www.");
document.write(unescape("%3Cscript src='" + gaJsHost + "google-analytics.com/ga.js' type='text/javascript'%3E%3C/script%3E"));
</script>
<script type="text/javascript">
try {
var pageTracker = _gat._getTracker("UA-9884254-1");
pageTracker._trackPageview();
} catch(err) {}
</script>
</body></html>
|
