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| author | Reinier Zwitserloot <reinier@zwitserloot.com> | 2015-01-26 08:46:41 +0100 |
|---|---|---|
| committer | Reinier Zwitserloot <reinier@zwitserloot.com> | 2015-01-26 08:46:41 +0100 |
| commit | 63aefa41e432a050496e9f96c6ce570dde276e18 (patch) | |
| tree | 4d5fb71e5d9c2a3dd865ede63c6b5ef70f0d1d0a /website/features/Builder.html | |
| parent | 7bb2ed02c3891d240840110abb0a79949947cc16 (diff) | |
| download | lombok-63aefa41e432a050496e9f96c6ce570dde276e18.tar.gz lombok-63aefa41e432a050496e9f96c6ce570dde276e18.tar.bz2 lombok-63aefa41e432a050496e9f96c6ce570dde276e18.zip | |
documentation for @Singular.
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| -rw-r--r-- | website/features/Builder.html | 172 |
1 files changed, 172 insertions, 0 deletions
diff --git a/website/features/Builder.html b/website/features/Builder.html new file mode 100644 index 00000000..e99f8525 --- /dev/null +++ b/website/features/Builder.html @@ -0,0 +1,172 @@ +<!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>@Builder</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>@Builder</h1> + <div class="byline">... and Bob's your uncle: No-hassle fancy-pants APIs for object creation!</div> + <div class="since"> + <h3>Since</h3> + <p> + <code>@Builder</code> was introduced as experimental feature in lombok v0.12.0. + </p><p> + <code>@Builder</code> gained <code>@Singular</code> support and was promoted to the main <code>lombok</code> package since lombok v1.16.0. + </p> + </div> + <div class="overview"> + <h3>Overview</h3> + <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> can be placed on a class, or on a constructor, or on a static 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 "static method" use-case. + </p><p> + A static method annotated with <code>@Builder</code> (from now on called the <em>target</em>) causes the following 7 things to be generated:<ul> + <li>An inner static class named <code><em>Foo</em>Builder</code>, with the same type arguments as the static method (called the <em>builder</em>).</li> + <li>In the <em>builder</em>: One private non-static non-final field for each parameter of the <em>target</em>.</li> + <li>In the <em>builder</em>: A package private no-args empty constructor.</li> + <li>In the <em>builder</em>: A 'setter'-like method for each parameter of the <em>target</em>: It has the same type as that parameter and the same name. + It returns the builder itself, so that the setter calls can be chained, as in the above example.</li> + <li>In the <em>builder</em>: A <code>build()</code> method which calls the static method, passing in each field. It returns the same type that the + <em>target</em> returns.</li> + <li>In the <em>builder</em>: A sensible <code>toString()</code> implementation.</li> + <li>In the class containing the <em>target</em>: A <code>builder()</code> method, which creates a new instance of the <em>builder</em>.</li> + </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<String> jobs</code> + field to have 2 strings in it. To get this behaviour, 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 "static 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> + Finally, applying <code>@Builder</code> to a class is as if you added <code>@AllArgsConstructor(access = AccessLevel.PACKAGE)</code> to the class and applied the + <code>@Builder</code> annotation to this all-args-constructor. This only works if you haven't written any explicit constructors yourself. If you do have an + explicit constructor, put the <code>@Builder</code> annotation on the constructor instead of on the class. + </p><p> + The name of the builder class is <code><em>Foobar</em>Builder</code>, where <em>Foobar</em> is the simplified, title-cased form of the return type of the + <em>target</em> - that is, the name of your type for <code>@Builder</code> on constructors and types, and the name of the return type for <code>@Builder</code> + on static methods. For example, if <code>@Builder</code> is applied to a class named <code>com.yoyodyne.FancyList<T></code>, then the builder name will be + <code>FancyListBuilder<T></code>. If <code>@Builder</code> is applied to a static method that returns <code>void</code>, the builder will be named + <code>VoidBuilder</code>. + </p><p> + The configurable aspects of builder are:<ul> + <li>The <em>builder's class name</em> (default: return type + 'Builder')</li> + <li>The <em>build()</em> method's name (default: <code>"build"</code>)</li> + <li>The <em>builder()</em> method's name (default: <code>"builder"</code>)</li> + </ul> + Example usage where all options are changed from their defaults:<br /> + <code>@Builder(builderClassName = "HelloWorldBuilder", buildMethodName = "execute", builderMethodName = "helloWorld")</code><br /> + </p> + </div> + <div class="overview"> + <h3><a name="singular">@Singular</a></h3> + <p> + By annotating one of the parameters (if annotating a static method or constructor with <code>@Builder</code>) or fields (if annotating a class with <code>@Builder</code>) with the + <code>@Singular</code> annotation, lombok will treat that builder node as a collection, and it generates 2 'adder' methods instead of a 'setter' method. One which adds a single element to the collection, and one + which adds all elements of another collection to the collection. No setter to just set the collection (replacing whatever was already added) will be generated. These 'singular' builders + are very complicated in order to guarantee the following properties: + <ul> + <li>When invoking <code>build()</code>, the produced collection will be immutable.</li> + <li>Repeatedly invoking <code>build()</code> works fine and does not corrupt any of the collections already generated.</li> + <li>Calling one of the 'adder' methods after invoking <code>build()</code> does not modify any already generated objects, and, if <code>build()</code> is later called again, + <li>The produced collection will be compacted to the smallest feasible format while remaining efficient.</li> + </ul> + </p><p> + <code>@Singular</code> can only be applied to collection types for which lombok has a recipe to produce the singular methods. Currently, the supported types are: + <ul> + <li><a href="http://docs.oracle.com/javase/8/docs/api/java/util/package-summary.html"><code>java.util</code></a>:<ul> + <li><code>Collection</code> and <code>List</code> (backed by a compacted unmodifiable <code>ArrayList</code> in the general case).</li> + <li><code>Set</code>, <code>SortedSet</code>, and <code>NavigableSet</code> (backed by a smartly sized unmodifiable <code>HashSet</code> or <code>TreeSet</code> in the general case).</li> + <li><code>Map</code>, <code>SortedMap</code>, and <code>NavigableMap</code> (backed by a smartly sized unmodifiable <code>HashMap</code> or <code>TreeMap</code> in the general case).</li> + </ul></li> + <li><a href="https://github.com/google/guava">Guava</a>'s <code>com.google.common.collect</code>:<ul> + <li><code>ImmutableCollection</code> and <code>ImmutableList</code> (backed by the builder feature of <code>ImmutableList</code>).</li> + <li><code>ImmutableSet</code> and <code>ImmutableSortedSet</code> (backed by the builder feature of those types).</li> + <li><code>ImmutableMap</code>, <code>ImmutableBiMap</code>, and ImmutableSortedMap</code> (backed by the builder feature of those types).</li> + </ul></li> + </ul> + </p><p> + If your identifiers are written in common english, lombok assumes that any collection with <code>@Singular</code> on it is an english plural and will attempt to automatically + singularize it. If this is possible, the add-one method will use this name. For example, if your collection is called <code>statuses</code>, then the add-one method will automatically + be called <code>status</code>. If lombok cannot singularize your identifier, or it is ambiguous, lombok will generate an error and force you to explicitly specify the singular name. + To do this, just pass the singular name as string, like so: <code>@Singular("axis") List<Line> axes;</code>. + </p><p> + When using the <code>java.util</code> interfaces, lombok always uses <code>ArrayList</code> to store items added to the builder, because this is more efficient than adding them to a map or + set immediately, as lombok needs to compact and potentially duplicate the result. + </p><p> + The snippet below does not show what lombok generates for a <code>@Singular</code> field/parameter because it is rather complicated. + You can view a snippet <a href="Singular-snippet.html">here</a>. + </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.builder.flagUsage</code> = [<code>warning</code> | <code>error</code>] (default: not set)</dt> + <dd>Lombok will flag any usage of <code>@Builder</code> as a warning or error if configured.</dd> + <dt><code>lombok.singular.useGuava</code> = [<code>true</code> | <code>false</code>] (default: false)</dt> + <dd>If <code>true</code>, lombok will use guava's <code>ImmutableX</code> builders and types to implement <code>java.util</code> collection interfaces, instead of creating + implementations based on <code>Collections.unmodifiableX</code>. You must ensure that guava is actually available on the classpath and buildpath if you use this setting. + Guava is used automatically if your field/parameter has one of the guava <code>ImmutableX</code> types. + <dt><code>lombok.singular.auto</code> = [<code>true</code> | <code>false</code>] (default: true)</dt> + <dd>If <code>true</code> (which is the default), lombok automatically tries to singularize your identifier name by assuming that it is a common english plural. + If <code>false</code>, you must always explicitly specify the singular name, and lombok will generate an error if you don't (useful if you write your code in a language other than english). + </dl> + </div> + <div class="overview"> + <h3>Small print</h3><div class="smallprint"> + <p> + @Singular support for <code>java.util.NavigableMap/Set</code> only works if you are compiling with JDK1.8 or higher. + </p><p> + You cannot manually provide some or all parts of a <code>@Singular</code> node; the code lombok generates is too complex for this. If you want to + manually control (part of) the builder nodes associated with some field or parameter, don't use @Singular and add everything you need manually. + </p><p> + The sorted collections (java.util: <code>SortedSet</code>, <code>NavigableSet</code>, <code>SortedMap</code>, <code>NavigableMap</code> and guava: <code>ImmutableSortedSet</code>, <code>ImmutableSortedMap</code>) require that the type argument of the collection has natural order (implements <code>java.util.Comparable</code>). There is no way to pass an explicit <code>Comparator</code> to use in the builder. + </p> + </div> + </div> + <div class="footer"> + <a href="index.html">Back to features</a> | <a href="Value.html">Previous feature (@Value)</a> | <a href="SneakyThrows.html">Next feature (@SneakyThrows)</a><br /> + <a href="../credits.html" class="creditsLink">credits</a> | <span class="copyright">Copyright © 2009-2014 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) ? 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