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class=docMainContainer_TBSr><div class="container padding-top--md padding-bottom--lg"><div class=row><div class="col docItemCol_VOVn"><div class=docItemContainer_Djhp><article><nav class="theme-doc-breadcrumbs breadcrumbsContainer_Z_bl" aria-label=Breadcrumbs><ul class=breadcrumbs><li class=breadcrumbs__item><a aria-label="Home page" class=breadcrumbs__link href=/><svg viewBox="0 0 24 24" class=breadcrumbHomeIcon_YNFT><path d="M10 19v-5h4v5c0 .55.45 1 1 1h3c.55 0 1-.45 1-1v-7h1.7c.46 0 .68-.57.33-.87L12.67 3.6c-.38-.34-.96-.34-1.34 0l-8.36 7.53c-.34.3-.13.87.33.87H5v7c0 .55.45 1 1 1h3c.55 0 1-.45 1-1z" fill=currentColor /></svg></a><li class=breadcrumbs__item><span class=breadcrumbs__link>Guide</span><li class=breadcrumbs__item><a class=breadcrumbs__link href=/docs/guide/kotlin/><span>Kotlin</span></a><li class="breadcrumbs__item breadcrumbs__item--active"><span class=breadcrumbs__link>Static Generated Serializers</span></ul></nav><span class="theme-doc-version-badge badge badge--secondary">Version: 1.3.0</span><div class="tocCollapsible_ETCw theme-doc-toc-mobile tocMobile_ITEo"><button type=button class="clean-btn tocCollapsibleButton_TO0P">On this page</button></div><div class="theme-doc-markdown markdown"><header><h1>Static Generated Serializers</h1></header><p>Use <code>fory-kotlin-ksp</code> when Kotlin classes must participate in Fory |
| cross-language schema serialization. The processor generates Kotlin source |
| serializers at build time. Those serializers call the existing Fory Java |
| implementation, including <code>WriteContext</code>, <code>ReadContext</code>, and <code>MemoryBuffer</code>; there is |
| no Kotlin-only protocol.</p> |
| <p>Static generated Kotlin serializers are for Kotlin/JVM and Android xlang/schema |
| mode. They are not Java native object serializers and do not preserve JVM object |
| graph implementation details such as the exact concrete collection class.</p> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=add-ksp>Add KSP<a href=#add-ksp class=hash-link aria-label="Direct link to Add KSP" title="Direct link to Add KSP" translate=no></a></h2> |
| <p>Add <code>fory-kotlin</code> to the application classpath and run <code>fory-kotlin-ksp</code> as a KSP processor in |
| the module that compiles your <code>@ForyStruct</code> Kotlin classes.</p> |
| <div class="language-kotlin codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-kotlin codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token plain">plugins </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token function" style=color:#d73a49>id</span><span class="token punctuation" style=color:#393A34>(</span><span class="token string-literal singleline string" style=color:#e3116c>"com.google.devtools.ksp"</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"> version </span><span class="token string-literal singleline string" style=color:#e3116c>"<ksp-version>"</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token punctuation" style=color:#393A34>}</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain">dependencies </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token function" style=color:#d73a49>implementation</span><span class="token punctuation" style=color:#393A34>(</span><span class="token string-literal singleline string" style=color:#e3116c>"org.apache.fory:fory-kotlin:<fory-version>"</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token function" style=color:#d73a49>ksp</span><span class="token punctuation" style=color:#393A34>(</span><span class="token string-literal singleline string" style=color:#e3116c>"org.apache.fory:fory-kotlin-ksp:<fory-version>"</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token punctuation" style=color:#393A34>}</span><br/></div></code></pre></div></div> |
| <p>For Android, configure KSP in the Android module or library module that owns |
| the Kotlin model classes.</p> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=define-a-struct>Define A Struct<a href=#define-a-struct class=hash-link aria-label="Direct link to Define A Struct" title="Direct link to Define A Struct" translate=no></a></h2> |
| <p>Reuse the Java Fory annotations for schema concepts. Use Kotlin type-use |
| annotations only when you need to override integer encoding.</p> |
| <div class="language-kotlin codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-kotlin codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token keyword" style=color:#00009f>import</span><span class="token plain"> org</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">apache</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">fory</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">annotation</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">ForyField</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>import</span><span class="token plain"> org</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">apache</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">fory</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">annotation</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">ForyStruct</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>import</span><span class="token plain"> org</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">apache</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">fory</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">kotlin</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">Fixed</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>import</span><span class="token plain"> org</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">apache</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">fory</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">kotlin</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">VarInt</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token annotation builtin">@ForyStruct</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>data</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>class</span><span class="token plain"> </span><span class="token function" style=color:#d73a49>User</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token annotation builtin">@ForyField</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">id </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> </span><span class="token number" style=color:#36acaa>1</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>val</span><span class="token plain"> id</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> </span><span class="token annotation builtin">@Fixed</span><span class="token plain"> UInt</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token annotation builtin">@ForyField</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">id </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> </span><span class="token number" style=color:#36acaa>2</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>val</span><span class="token plain"> score</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> </span><span class="token annotation builtin">@VarInt</span><span class="token plain"> Long</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token annotation builtin">@ForyField</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">id </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> </span><span class="token number" style=color:#36acaa>3</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>val</span><span class="token plain"> tags</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> List</span><span class="token operator" style=color:#393A34><</span><span class="token plain">String</span><span class="token operator" style=color:#393A34>></span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token punctuation" style=color:#393A34>)</span><br/></div></code></pre></div></div> |
| <p>Use <code>@ForyField(id = 1)</code> on constructor properties. <code>@field:ForyField(id = 1)</code> |
| is also accepted for field-backed properties. Do not use <code>@get:ForyField</code> or |
| <code>@set:ForyField</code>; accessors are not schema fields and the processor rejects |
| them.</p> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=supported-structs>Supported Structs<a href=#supported-structs class=hash-link aria-label="Direct link to Supported Structs" title="Direct link to Supported Structs" translate=no></a></h2> |
| <p>The processor generates serializers for public or internal, concrete, |
| non-generic classes in named packages. A supported class must have a primary |
| constructor whose serialized parameters are <code>val</code> or <code>var</code> properties. <code>data class</code> is the common case, but it is not required.</p> |
| <p>Internal Kotlin struct classes are supported when KSP runs in the same Kotlin |
| module that owns the struct. The generated Kotlin serializer is also internal, |
| so it can call the internal constructor and expose the internal type in |
| overrides while still producing a JVM class that Fory Java can load. |
| Application code outside that Kotlin module still cannot refer to the internal |
| struct directly, so registration must happen from code that can see the class.</p> |
| <p>The processor rejects these declarations:</p> |
| <ul> |
| <li class=""><code>private</code> struct classes.</li> |
| <li class="">local, anonymous, or nested <code>@ForyStruct</code> classes.</li> |
| <li class="">Kotlin <code>object</code> declarations.</li> |
| <li class="">interfaces, abstract classes, and sealed classes as serializer targets.</li> |
| <li class="">generic <code>@ForyStruct</code> classes.</li> |
| <li class="">private constructor properties.</li> |
| <li class="">private or protected primary constructors.</li> |
| </ul> |
| <p>Kotlin default constructor arguments are supported for compatible reads. A |
| struct can have up to 12 defaulted constructor fields.</p> |
| <p>Constructor-based generated serializers support wide primary constructors. |
| Compatible reads track remote field presence in generated side state instead of |
| using constructor bit masks.</p> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=nullability>Nullability<a href=#nullability class=hash-link aria-label="Direct link to Nullability" title="Direct link to Nullability" translate=no></a></h2> |
| <p>Use Kotlin <code>?</code> to describe nullable schema positions. Nullability is preserved |
| inside collections and maps.</p> |
| <div class="language-kotlin codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-kotlin codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token annotation builtin">@ForyStruct</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>data</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>class</span><span class="token plain"> </span><span class="token function" style=color:#d73a49>NullabilityExample</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token annotation builtin">@ForyField</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">id </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> </span><span class="token number" style=color:#36acaa>1</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>val</span><span class="token plain"> a</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> List</span><span class="token operator" style=color:#393A34><</span><span class="token plain">String</span><span class="token operator" style=color:#393A34>></span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token annotation builtin">@ForyField</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">id </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> </span><span class="token number" style=color:#36acaa>2</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>val</span><span class="token plain"> b</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> List</span><span class="token operator" style=color:#393A34><</span><span class="token plain">String</span><span class="token operator" style=color:#393A34>?</span><span class="token operator" style=color:#393A34>></span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token annotation builtin">@ForyField</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">id </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> </span><span class="token number" style=color:#36acaa>3</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>val</span><span class="token plain"> c</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> List</span><span class="token operator" style=color:#393A34><</span><span class="token plain">String</span><span class="token operator" style=color:#393A34>></span><span class="token operator" style=color:#393A34>?</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token annotation builtin">@ForyField</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">id </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> </span><span class="token number" style=color:#36acaa>4</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>val</span><span class="token plain"> d</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> List</span><span class="token operator" style=color:#393A34><</span><span class="token plain">String</span><span class="token operator" style=color:#393A34>?</span><span class="token operator" style=color:#393A34>></span><span class="token operator" style=color:#393A34>?</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token punctuation" style=color:#393A34>)</span><br/></div></code></pre></div></div> |
| <p>Do not use Fory <code>@Nullable</code> in hand-written constructor-based Kotlin structs. |
| The KSP processor rejects it so the schema is always read from Kotlin source |
| nullability. Compiler-generated Kotlin IDL sources follow the same rule and use |
| Kotlin <code>?</code> for nullable fields.</p> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=references>References<a href=#references class=hash-link aria-label="Direct link to References" title="Direct link to References" translate=no></a></h2> |
| <p>Kotlin generated serializers preserve <code>@Ref</code> metadata for fields, list |
| elements, and map values. Constructor-owned reads construct Kotlin values |
| through primary constructors. Schema IDL classes that need reference |
| publication are emitted as mutable no-arg classes, and their KSP-generated |
| serializers publish the instance before reading fields. In both shapes, KSP owns |
| field descriptors, nested nullability, and <code>@Ref</code> metadata.</p> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=collections>Collections<a href=#collections class=hash-link aria-label="Direct link to Collections" title="Direct link to Collections" translate=no></a></h2> |
| <p>Collection declarations carry schema shape, not JVM implementation identity. |
| For example, <code>List<String></code> is encoded as <code>list<string></code> and |
| <code>Map<String, Int></code> is encoded as <code>map<string, int32></code>.</p> |
| <p>Deserialization only guarantees that the result is assignable to the declared |
| field type. Fory does not preserve whether the original concrete value was an |
| <code>ArrayList</code>, <code>LinkedList</code>, <code>Collections.unmodifiableList</code>, synchronized |
| collection wrapper, or another JVM-specific collection implementation.</p> |
| <p>Supported collection declarations include Kotlin and Java list, set, and map |
| types. Mutable collection interface fields are deserialized to mutable |
| implementations assignable to the declared type. Sorted collections without an |
| explicit comparator, such as <code>TreeSet</code> and <code>ConcurrentSkipListSet</code>, are accepted |
| only for non-null scalar or string elements. Concurrent map declarations are |
| accepted only with non-null values because JVM concurrent map implementations |
| reject null entries.</p> |
| <p><code>Set<*></code>, <code>Map<*, T></code>, <code>Map<*, *></code>, and raw Java collections are rejected. |
| <code>List<*></code> and <code>Map<K, *></code> are accepted and use dynamic nullable values.</p> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=dense-arrays>Dense Arrays<a href=#dense-arrays class=hash-link aria-label="Direct link to Dense Arrays" title="Direct link to Dense Arrays" translate=no></a></h2> |
| <p>Kotlin dense primitive and unsigned array fields are supported:</p> |
| <ul> |
| <li class=""><code>BooleanArray</code></li> |
| <li class=""><code>ByteArray</code></li> |
| <li class=""><code>ShortArray</code></li> |
| <li class=""><code>IntArray</code></li> |
| <li class=""><code>LongArray</code></li> |
| <li class=""><code>FloatArray</code></li> |
| <li class=""><code>DoubleArray</code></li> |
| <li class=""><code>UByteArray</code></li> |
| <li class=""><code>UShortArray</code></li> |
| <li class=""><code>UIntArray</code></li> |
| <li class=""><code>ULongArray</code></li> |
| </ul> |
| <p>Dense arrays with unambiguous Kotlin carriers are supported in fields, |
| collection elements, map values, and union cases. <code>array<float16></code> and |
| <code>array<bfloat16></code> use the Java core <code>Float16Array</code> and <code>BFloat16Array</code> carriers.</p> |
| <p><code>ByteArray</code> is encoded as Fory <code>binary</code> unless the <code>ByteArray</code> type use is |
| annotated with Java <code>@ArrayType</code>. Generated Kotlin IDL uses |
| <code>@ArrayType ByteArray</code> for <code>array<int8></code>, including nested collection and map |
| positions.</p> |
| <p><code>@ArrayType</code> is also supported on top-level <code>List<T></code> fields when <code>T</code> is a |
| non-null boolean or numeric dense-array element type. In that case the field is |
| encoded as dense <code>array<T></code> schema, and generated reads convert decoded JVM list |
| elements back to the declared Kotlin element carrier.</p> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=integer-encoding>Integer Encoding<a href=#integer-encoding class=hash-link aria-label="Direct link to Integer Encoding" title="Direct link to Integer Encoding" translate=no></a></h2> |
| <p>Kotlin type-use encoding annotations map to Fory xlang integer encodings:</p> |
| <table><thead><tr><th>Annotation<th>Valid Kotlin types<tbody><tr><td><code>@Fixed</code><td><code>Int</code>, <code>Long</code>, <code>UInt</code>, <code>ULong</code><tr><td><code>@VarInt</code><td><code>Int</code>, <code>Long</code>, <code>UInt</code>, <code>ULong</code><tr><td><code>@Tagged</code><td><code>Long</code>, <code>ULong</code></table> |
| <p>Without an annotation, xlang <code>Int</code>, <code>Long</code>, <code>UInt</code>, and <code>ULong</code> use varint |
| encoding. This is required by xlang mode and is not controlled by Java native |
| mode numeric compression options.</p> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=duration>Duration<a href=#duration class=hash-link aria-label="Direct link to Duration" title="Direct link to Duration" translate=no></a></h2> |
| <p>Xlang <code>duration</code> maps to <code>kotlin.time.Duration</code>. Infinite Kotlin durations |
| cannot be represented by the xlang duration payload and fail during |
| serialization.</p> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=sealed-unions>Sealed Unions<a href=#sealed-unions class=hash-link aria-label="Direct link to Sealed Unions" title="Direct link to Sealed Unions" translate=no></a></h2> |
| <p>KSP generates serializers for top-level sealed classes annotated with |
| <code>@ForyUnion</code>. Each schema case is a nested class annotated with <code>@ForyCase</code> and |
| one constructor property named <code>value</code>. <code>Unknown(UnknownCase)</code> is marked with |
| <code>@ForyUnknownCase</code> as the Fory-owned forward-compatibility carrier. It is |
| omitted from the schema case table because the marker only selects the carrier |
| and does not add a schema entry. A typed union must declare at least one |
| non-<code>Unknown</code> case:</p> |
| <div class="language-kotlin codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-kotlin codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token keyword" style=color:#00009f>package</span><span class="token plain"> example</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>import</span><span class="token plain"> org</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">apache</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">fory</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">annotation</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">ForyCase</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>import</span><span class="token plain"> org</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">apache</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">fory</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">annotation</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">ForyUnion</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>import</span><span class="token plain"> org</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">apache</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">fory</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">annotation</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">ForyUnknownCase</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>import</span><span class="token plain"> org</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">apache</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">fory</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">type</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">union</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">UnknownCase</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token annotation builtin">@ForyUnion</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>sealed</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>class</span><span class="token plain"> Animal </span><span class="token punctuation" style=color:#393A34>{</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token annotation builtin">@ForyUnknownCase</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>data</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>class</span><span class="token plain"> </span><span class="token function" style=color:#d73a49>Unknown</span><span class="token punctuation" style=color:#393A34>(</span><span class="token keyword" style=color:#00009f>val</span><span class="token plain"> value</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> UnknownCase</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"> </span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> </span><span class="token function" style=color:#d73a49>Animal</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token annotation builtin">@ForyCase</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">id </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> </span><span class="token number" style=color:#36acaa>0</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token keyword" style=color:#00009f>data</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>class</span><span class="token plain"> </span><span class="token function" style=color:#d73a49>Dog</span><span class="token punctuation" style=color:#393A34>(</span><span class="token keyword" style=color:#00009f>val</span><span class="token plain"> value</span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> example</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">Dog</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"> </span><span class="token operator" style=color:#393A34>:</span><span class="token plain"> </span><span class="token function" style=color:#d73a49>Animal</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token punctuation" style=color:#393A34>}</span><br/></div></code></pre></div></div> |
| <p>When a generated Kotlin union case name matches the payload type simple name, |
| packaged output keeps the case name and qualifies the payload type. If a target |
| output mode cannot express a legal qualifier for a conflict, the IDL compiler |
| appends <code>Case</code> to the generated case class name.</p> |
| <p>Generated schema modules register sealed unions through <code>KotlinSerializers.registerUnion</code>. |
| Fory discovers the generated <code><Target>_ForySerializer</code> automatically, so |
| callers do not pass a serializer instance.</p> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=register-classes>Register Classes<a href=#register-classes class=hash-link aria-label="Direct link to Register Classes" title="Direct link to Register Classes" translate=no></a></h2> |
| <p>Register Kotlin struct classes with the Kotlin <code>register<T></code> extension. You |
| choose the xlang namespace and type name; generated serializers do not choose |
| IDs or names for you.</p> |
| <div class="language-kotlin codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-kotlin codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token keyword" style=color:#00009f>import</span><span class="token plain"> org</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">apache</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">fory</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">kotlin</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">ForyKotlin</span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>import</span><span class="token plain"> org</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">apache</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">fory</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">kotlin</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">register</span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"></span><span class="token keyword" style=color:#00009f>val</span><span class="token plain"> fory </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> ForyKotlin</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>builder</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>withXlang</span><span class="token punctuation" style=color:#393A34>(</span><span class="token boolean" style=color:#36acaa>true</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>requireClassRegistration</span><span class="token punctuation" style=color:#393A34>(</span><span class="token boolean" style=color:#36acaa>true</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>build</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain" style=display:inline-block></span><br/></div><div class=token-line style=color:#393A34><span class="token plain">fory</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">register</span><span class="token operator" style=color:#393A34><</span><span class="token plain">User</span><span class="token operator" style=color:#393A34>></span><span class="token punctuation" style=color:#393A34>(</span><span class="token string-literal singleline string" style=color:#e3116c>"example.User"</span><span class="token punctuation" style=color:#393A34>)</span><br/></div></code></pre></div></div> |
| <p><code>ForyKotlin.builder()</code> installs the Kotlin serializer bootstrap for the Fory |
| instance. The <code>fory.register<T>(...)</code> extension registers your xlang schema type |
| name and resolves the generated serializer from the target class.</p> |
| <p>Do not register or reference generated serializer classes in application code. |
| Fory resolves them from the registered target class.</p> |
| <p>Generated Schema IDL modules use the same path. They call |
| <code>KotlinSerializers.registerType</code>, <code>registerSerializer</code>, <code>registerEnum</code>, and |
| <code>registerUnion</code> as appropriate and never emit Java files.</p> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=generated-names>Generated Names<a href=#generated-names class=hash-link aria-label="Direct link to Generated Names" title="Direct link to Generated Names" translate=no></a></h2> |
| <p>The generated serializer is emitted in the same package as the target class. |
| Its name is <code><target>_ForySerializer</code>. For nested binary names, <code>$</code> is encoded |
| as <code>_</code>; source underscores are encoded as <code>_u_</code>.</p> |
| <p>These names are an implementation detail. They matter for diagnostics and |
| Android shrinking, but user code should only register target classes.</p> |
| <p>If a constructor-owned Kotlin xlang struct is registered but its KSP generated |
| serializer is missing, Fory fails with a configuration error. Compile generated |
| IDL sources with KSP before registering generated Kotlin classes.</p> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=android-and-r8>Android And R8<a href=#android-and-r8 class=hash-link aria-label="Direct link to Android And R8" title="Direct link to Android And R8" translate=no></a></h2> |
| <p>Android apps should not need user-written keep rules for generated Kotlin |
| serializers. KSP emits generated consumer R8/ProGuard rules under |
| <code>META-INF/proguard/</code> for the generated serializer constructors used by Fory and |
| the Kotlin metadata needed to detect required Kotlin generated serializers.</p> |
| <p>For library modules, package the generated <code>META-INF/proguard/</code> resources into |
| the produced artifact. For Android application modules, make sure your KSP |
| setup includes generated resources in the minified variant.</p> |
| <p>See <a class="" href=/docs/guide/kotlin/android_support>Android Support</a> for Android Gradle setup and |
| release-minified validation guidance.</p> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=native-object-mode>Native Object Mode<a href=#native-object-mode class=hash-link aria-label="Direct link to Native Object Mode" title="Direct link to Native Object Mode" translate=no></a></h2> |
| <p>Kotlin KSP generated serializers are only for xlang/schema mode. They do not |
| replace Fory Java native object serializers and do not preserve JVM object graph |
| identity. If you use Fory with <code>withXlang(false)</code>, Fory uses the normal Java and |
| Kotlin serializers instead.</p> |
| <p>Kotlin/Native and Kotlin/JS are not supported by this module.</div><footer class="theme-doc-footer docusaurus-mt-lg"><div class="row margin-top--sm theme-doc-footer-edit-meta-row"><div class="col noPrint_WFHX"><a href=https://github.com/apache/fory-site/tree/main/docs/guide/kotlin/static-generated-serializers.md target=_blank rel="noopener noreferrer" class=theme-edit-this-page><svg fill=currentColor height=20 width=20 viewBox="0 0 40 40" class=iconEdit_Z9Sw aria-hidden=true><g><path d="m34.5 11.7l-3 3.1-6.3-6.3 3.1-3q0.5-0.5 1.2-0.5t1.1 0.5l3.9 3.9q0.5 0.4 0.5 1.1t-0.5 1.2z m-29.5 17.1l18.4-18.5 6.3 6.3-18.4 18.4h-6.3v-6.2z"/></g></svg>Edit this page</a></div><div class="col lastUpdated_JAkA"></div></div></footer></article><nav class="docusaurus-mt-lg pagination-nav" aria-label="Docs pages"><a class="pagination-nav__link pagination-nav__link--prev" href=/docs/guide/kotlin/default_values><div class=pagination-nav__sublabel>Previous</div><div class=pagination-nav__label>Default 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| Copyright © 2026 The Apache Software Foundation, Licensed under the Apache License, Version 2.0. <br/> |
| Apache Fory, Fory, Apache, the Apache Logo and the Apache Fory logo are either registered trademarks or trademarks of the Apache Software Foundation in the United States and/or other countries. |
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