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| 1 | +<#import "_features.html" as f> |
| 2 | + |
| 3 | +<@f.scaffold title="@With" logline="Immutable 'setters' - methods that create a clone but with one changed field."> |
| 4 | + <@f.history> |
| 5 | + <p> |
| 6 | + <code>@Wither</code> was introduced as experimental feature in lombok v0.11.4. |
| 7 | + </p><p> |
| 8 | + <code>@Wither</code> was renamed to <code>@With</code>, and moved out of experimental and into the core package, in lombok v1.18.10. |
| 9 | + </@f.history> |
| 10 | + |
| 11 | + <@f.overview> |
| 12 | + <p> |
| 13 | + The next best alternative to a setter for an immutable property is to construct a clone of the object, but with a new value for this one field. A method to generate this clone is precisely what <code>@With</code> generates: a <code>withFieldName(newValue)</code> method which produces a clone except for the new value for the associated field. |
| 14 | + </p><p> |
| 15 | + For example, if you create <code>public class Point { private final int x, y; }</code>, setters make no sense because the fields are final. <code>@With</code> can generate a <code>withX(int newXValue)</code> method for you which will return a new point with the supplied value for <code>x</code> and the same value for <code>y</code>. |
| 16 | + </p><p> |
| 17 | + Like <a href="/features/GetterSetter"><code>@Setter</code></a>, you can specify an access level in case you want the generated with method to be something other than <code>public</code>:<br /> <code>@With(level = AccessLevel.PROTECTED)</code>. Also like <a href="/features/GetterSetter"><code>@Setter</code></a>, you can also put a <code>@With</code> annotation on a type, which means a <code>with</code> method is generated for each field (even non-final fields). |
| 18 | + </p><p> |
| 19 | + To put annotations on the generated method, you can use <code>onMethod=@__({@AnnotationsHere})</code>. Be careful though! This is an experimental feature. For more details see the documentation on the <a href="/features/experimental/onX">onX</a> feature. |
| 20 | + </p><p> |
| 21 | + javadoc on the field will be copied to generated with methods. Normally, all text is copied, and <code>@param</code> is <em>moved</em> to the with method, whilst <code>@return</code> lines are stripped from the with method's javadoc. Moved means: Deleted from the field's javadoc. It is also possible to define unique text for the with method's javadoc. To do that, you create a 'section' named <code>WITH</code>. A section is a line in your javadoc containing 2 or more dashes, then the text 'WITH', followed by 2 or more dashes, and nothing else on the line. If you use sections, <code>@return</code> and <code>@param</code> stripping / copying for that section is no longer done (move the <code>@param</code> line into the section). |
| 22 | + </p><p> |
| 23 | + If you have a hierarchical immutable data structure, the <a href="/features/experimental/WithBy"><code>@WithBy</code></a> feature might be more suitable than <code>@With</code> |
| 24 | + </@f.overview> |
| 25 | + |
| 26 | + <@f.snippets name="With" /> |
| 27 | + |
| 28 | + <@f.confKeys> |
| 29 | + <dt> |
| 30 | + <code>lombok.with.flagUsage</code> = [<code>warning</code> | <code>error</code>] (default: not set) |
| 31 | + </dt><dd> |
| 32 | + Lombok will flag any usage of <code>@With</code> as a warning or error if configured. |
| 33 | + </dd> |
| 34 | + </@f.confKeys> |
| 35 | + |
| 36 | + <@f.smallPrint> |
| 37 | + <p> |
| 38 | + With methods cannot be generated for static fields because that makes no sense. |
| 39 | + </p><p> |
| 40 | + With methods can be generated for abstract classes, but this generates an abstract method with the appropriate signature. |
| 41 | + </p><p> |
| 42 | + When applying <code>@With</code> to a type, static fields and fields whose name start with a $ are skipped. |
| 43 | + </p><p> |
| 44 | + For generating the method names, the first character of the field, if it is a lowercase character, is title-cased, otherwise, it is left unmodified. Then, <code>with</code> is prefixed. |
| 45 | + </p><p> |
| 46 | + No method is generated if any method already exists with the same name (case insensitive) and same parameter count. For example, <code>withX(int x)</code> will not be generated if there's already a method <code>withX(String... x)</code> even though it is technically possible to make the method. This caveat exists to prevent confusion. If the generation of a method is skipped for this reason, a warning is emitted instead. Varargs count as 0 to N parameters. |
| 47 | + </p><p> |
| 48 | + For <code>boolean</code> fields that start with <code>is</code> immediately followed by a title-case letter, nothing is prefixed to generate the wither name. |
| 49 | + </p><p> |
| 50 | + Various well known annotations about nullity cause null checks to be inserted and will be copied to the parameter. See <a href="/features/GetterSetter">Getter/Setter</a> documentation's small print for more information. |
| 51 | + </p> |
| 52 | + </@f.smallPrint> |
| 53 | +</@f.scaffold> |
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