Improve Builder documentation to emphasize the "builder()" factory method. Fixes #2870

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Roel Spilker committed 2021-06-10 22:25:23 +02:00
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@@ -268,6 +268,10 @@ ol.snippet.cmd li:before {
content: ">\A0\A0";
}
ol.snippet li.continued {
padding-left: 2em;
}
.fork-me {
position: fixed;
width: 150px;
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@@ -21,9 +21,17 @@
<p>
The <code>@Builder</code> annotation produces complex builder APIs for your classes.
</p><p>
<code>@Builder</code> lets you automatically produce the code required to have your class be instantiable with code such as:<br />
<code>Person.builder().name("Adam Savage").city("San Francisco").job("Mythbusters").job("Unchained Reaction").build();</code>
</p><p>
<code>@Builder</code> lets you automatically produce the code required to have your class be instantiable with code such as:
</p>
<ol class="snippet example">
<li>Person.builder()</li>
<li class="continued">.name("Adam Savage")</li>
<li class="continued">.city("San Francisco")</li>
<li class="continued">.job("Mythbusters")</li>
<li class="continued">.job("Unchained Reaction")</li>
<li class="continued">.build();</li>
</ol>
<p>
<code>@Builder</code> can be placed on a class, or on a constructor, or on a method. While the "on a class" and "on a constructor" mode are the most common use-case, <code>@Builder</code> is most easily explained with the "method" use-case.
</p><p>
A method annotated with <code>@Builder</code> (from now on called the <em>target</em>) causes the following 7 things to be generated:
@@ -46,7 +54,15 @@
</ul>
Each listed generated element will be silently skipped if that element already exists (disregarding parameter counts and looking only at names). This includes the <em>builder</em> itself: If that class already exists, lombok will simply start injecting fields and methods inside this already existing class, unless of course the fields / methods to be injected already exist. You may not put any other method (or constructor) generating lombok annotation on a builder class though; for example, you can not put <code>@EqualsAndHashCode</code> on the builder class.
</p><p>
<code>@Builder</code> can generate so-called 'singular' methods for collection parameters/fields. These take 1 element instead of an entire list, and add the element to the list. For example: <code>Person.builder().job("Mythbusters").job("Unchained Reaction").build();</code> would result in the <code>List&lt;String&gt; jobs</code> field to have 2 strings in it. To get this behavior, the field/parameter needs to be annotated with <code>@Singular</code>. The feature has <a href="#singular">its own documentation</a>.
<code>@Builder</code> can generate so-called 'singular' methods for collection parameters/fields. These take 1 element instead of an entire list, and add the element to the list. For example:
</p>
<ol class="snippet example">
<li>Person.builder()</li>
<li class="continued">.job("Mythbusters")</li>
<li class="continued">.job("Unchained Reaction")</li>
<li class="continued">.build();</li>
</ol>
<p>would result in the <code>List&lt;String&gt; jobs</code> field to have 2 strings in it. To get this behavior, the field/parameter needs to be annotated with <code>@Singular</code>. The feature has <a href="#singular">its own documentation</a>.
</p><p>
Now that the "method" mode is clear, putting a <code>@Builder</code> annotation on a constructor functions similarly; effectively, constructors are just static methods that have a special syntax to invoke them: Their 'return type' is the class they construct, and their type parameters are the same as the type parameters of the class itself.
</p><p>