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menu__link--sublist menu__link--sublist-caret" role=button aria-expanded=false href=/docs/json/><span class=categoryLinkLabel_W154>Fory JSON</span></a></div><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class=menu__list-item-collapsible><a class="categoryLink_byQd menu__link menu__link--sublist menu__link--sublist-caret" role=button aria-expanded=false href=/docs/compiler/><span class=categoryLinkLabel_W154>Fory IDL & Compiler</span></a></div><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class=menu__list-item-collapsible><a class="categoryLink_byQd menu__link menu__link--sublist menu__link--sublist-caret" role=button aria-expanded=false href=/docs/grpc/><span class=categoryLinkLabel_W154>Fory gRPC</span></a></div><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class=menu__list-item-collapsible><a class="categoryLink_byQd menu__link menu__link--sublist menu__link--sublist-caret" role=button aria-expanded=false href=/docs/development/><span class=categoryLinkLabel_W154>Development</span></a></div></ul></nav></div></div></aside><main 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>Object Serialization</span><li class="breadcrumbs__item breadcrumbs__item--active"><span class=breadcrumbs__link>Xlang Serialization</span></ul></nav><span class="theme-doc-version-badge badge badge--secondary">Version: 1.7</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>Xlang Serialization</h1></header><p>Xlang is Fory's default object serialization mode. It uses one portable binary format across Java, |
| Python, C++, Go, Rust, JavaScript/TypeScript, C#, Swift, Dart, Scala, and Kotlin. Each |
| language-specific <a href=#language-guides class="">Basic Serialization</a> page documents the relevant API and model |
| examples; this page explains the rules that peers must share.</p> |
| <p>Read <a class="" href=/docs/object-serialization/core-concepts>Core Concepts</a> first for the object graph, schema, reference, and |
| polymorphism concepts shared by xlang and native modes.</p> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=overview>Overview<a href=#overview class=hash-link aria-label="Direct link to Overview" title="Direct link to Overview" translate=no></a></h2> |
| <p>Use xlang serialization when bytes cross language boundaries, including polyglot services, data |
| pipelines, and frontend/backend communication. It provides:</p> |
| <ul> |
| <li class="">Direct serialization of native language models without requiring an IDL.</li> |
| <li class="">Coordinated numeric or named identities for application types.</li> |
| <li class="">Compatible schema evolution for independently deployed peers.</li> |
| <li class="">Optional shared-reference and circular-reference preservation.</li> |
| <li class="">Polymorphic values when every concrete type has a portable mapping.</li> |
| <li class="">Out-of-band buffers for large binary and numeric data where the Fory implementation supports them.</li> |
| </ul> |
| <p>Use <a class="" href=/docs/object-serialization/native>Native Serialization</a> instead when every writer and reader uses one supported Fory |
| implementation family and the object graph needs language-specific behavior such as Java |
| serialization hooks or Python pickle-compatible objects.</p> |
| <h3 class="anchor anchorTargetStickyNavbar_Vzrq" id=supported-languages>Supported Languages<a href=#supported-languages class=hash-link aria-label="Direct link to Supported Languages" title="Direct link to Supported Languages" translate=no></a></h3> |
| <table><thead><tr><th>Language<th>Package or target<th>Modes<tbody><tr><td>Java<td><code>org.apache.fory:fory-core</code><td>xlang/native<tr><td>Python<td><code>pyfory</code><td>xlang/native<tr><td>C++<td>Fory C++ CMake or Bazel target<td>xlang/native<tr><td>Go<td><code>github.com/apache/fory/go/fory</code><td>xlang/native<tr><td>Rust<td><code>fory</code> crate<td>xlang/native<tr><td>JavaScript/TypeScript<td><code>@apache-fory/core</code><td>xlang<tr><td>C#<td><code>Apache.Fory</code><td>xlang<tr><td>Swift<td><code>Fory</code> Swift Package Manager target<td>xlang<tr><td>Dart<td><code>fory</code> package<td>xlang<tr><td>Scala<td><code>org.apache.fory:fory-scala</code><td>xlang/native<tr><td>Kotlin<td><code>org.apache.fory:fory-kotlin</code> and Java API<td>xlang/native</table> |
| <h3 class="anchor anchorTargetStickyNavbar_Vzrq" id=first-cross-language-round-trip>First Cross-Language Round Trip<a href=#first-cross-language-round-trip class=hash-link aria-label="Direct link to First Cross-Language Round Trip" title="Direct link to First Cross-Language Round Trip" translate=no></a></h3> |
| <p>Register the same logical type identity and compatible fields on every peer. The following example |
| uses a shared type name.</p> |
| <p>Rust producer:</p> |
| <div class="language-rust codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-rust 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>use</span><span class="token plain"> </span><span class="token namespace" style=opacity:0.7>fory</span><span class="token namespace punctuation" style=opacity:0.7;color:#393A34>::</span><span class="token punctuation" style=color:#393A34>{</span><span class="token class-name">Fory</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> </span><span class="token class-name">ForyStruct</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 attribute attr-name" style=color:#00a4db>#[derive(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>struct</span><span class="token plain"> </span><span class="token type-definition class-name">Person</span><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"> name</span><span class="token punctuation" style=color:#393A34>:</span><span class="token plain"> </span><span class="token class-name">String</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"> age</span><span class="token punctuation" style=color:#393A34>:</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>i32</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 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 keyword" style=color:#00009f>let</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>mut</span><span class="token plain"> fory </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> </span><span class="token class-name">Fory</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 punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>xlang</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 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 punctuation" style=color:#393A34>;</span><span class="token plain"></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 function" style=color:#d73a49>register_by_name</span><span class="token punctuation" style=color:#393A34>::</span><span class="token operator" style=color:#393A34><</span><span class="token class-name">Person</span><span class="token operator" style=color:#393A34>></span><span class="token punctuation" style=color:#393A34>(</span><span class="token string" style=color:#e3116c>"example.Person"</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>unwrap</span><span class="token punctuation" style=color:#393A34>(</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 keyword" style=color:#00009f>let</span><span class="token plain"> person </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> </span><span class="token class-name">Person</span><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"> name</span><span class="token punctuation" style=color:#393A34>:</span><span class="token plain"> </span><span class="token string" style=color:#e3116c>"Alice"</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>to_string</span><span class="token punctuation" style=color:#393A34>(</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"> age</span><span class="token punctuation" style=color:#393A34>:</span><span class="token plain"> </span><span class="token number" style=color:#36acaa>30</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 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>let</span><span class="token plain"> bytes </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> fory</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>serialize</span><span class="token punctuation" style=color:#393A34>(</span><span class="token operator" style=color:#393A34>&</span><span class="token plain">person</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>unwrap</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><br/></div></code></pre></div></div> |
| <p>Python consumer:</p> |
| <div class="language-python codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-python 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>from</span><span class="token plain"> dataclasses </span><span class="token keyword" style=color:#00009f>import</span><span class="token plain"> dataclass</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"> pyfory</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 decorator annotation punctuation" style=color:#393A34>@dataclass</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>class</span><span class="token plain"> </span><span class="token class-name">Person</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"> name</span><span class="token punctuation" style=color:#393A34>:</span><span class="token plain"> </span><span class="token builtin">str</span><span class="token plain"></span><br/></div><div class=token-line style=color:#393A34><span class="token plain"> age</span><span class="token punctuation" style=color:#393A34>:</span><span class="token plain"> pyfory</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">Int32</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 operator" style=color:#393A34>=</span><span class="token plain"> pyfory</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">xlang</span><span class="token operator" 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">fory</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">register_type</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">Person</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> name</span><span class="token operator" style=color:#393A34>=</span><span class="token string" style=color:#e3116c>"example.Person"</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">person </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> fory</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">deserialize</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">bytes_from_rust</span><span class="token punctuation" style=color:#393A34>)</span><br/></div></code></pre></div></div> |
| <p>Although xlang is the default, examples often select it explicitly so the transport contract is |
| visible in application code.</p> |
| <h3 class="anchor anchorTargetStickyNavbar_Vzrq" id=native-models-or-fory-idl>Native Models or Fory IDL<a href=#native-models-or-fory-idl class=hash-link aria-label="Direct link to Native Models or Fory IDL" title="Direct link to Native Models or Fory IDL" translate=no></a></h3> |
| <table><thead><tr><th>Approach<th>Use when<tbody><tr><td>Native language models<td>The contract is small and teams want to start without a compiler step<tr><td><a class="" href=/docs/compiler/>Fory IDL</a><td>Many messages or teams need one schema and generated models<tr><td>Native first, then migrate to IDL<td>A small contract is becoming a long-lived, multi-team service boundary</table> |
| <p>A minimal Fory IDL message looks like this:</p> |
| <div class="language-protobuf codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-protobuf 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><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 keyword" style=color:#00009f>message</span><span class="token plain"> </span><span class="token class-name">Person</span><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"> </span><span class="token builtin">string</span><span class="token plain"> name </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 builtin">int32</span><span class="token plain"> age </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>optional</span><span class="token plain"> </span><span class="token builtin">string</span><span class="token plain"> email </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 punctuation" style=color:#393A34>}</span><br/></div></code></pre></div></div> |
| <p>Generate the required language targets with <code>foryc</code>; generated models use consistent field and type |
| metadata across those targets.</p> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=type-system-and-type-identity>Type System and Type Identity<a href=#type-system-and-type-identity class=hash-link aria-label="Direct link to Type System and Type Identity" title="Direct link to Type System and Type Identity" translate=no></a></h2> |
| <h3 class="anchor anchorTargetStickyNavbar_Vzrq" id=built-in-and-custom-types>Built-in and Custom Types<a href=#built-in-and-custom-types class=hash-link aria-label="Direct link to Built-in and Custom Types" title="Direct link to Built-in and Custom Types" translate=no></a></h3> |
| <p>Primitive numeric values, strings, binary values, temporal values, lists, sets, maps, dense numeric |
| arrays, enums, structs, and unions have shared xlang schemas. Built-in values do not require user |
| registration. Application structs, enums, unions, and extension types require a coordinated |
| identity.</p> |
| <p>The normative <a class="" href=/docs/specification/xlang_type_mapping>type mapping</a> defines the exact host-language |
| carrier for every xlang type. Important cases include:</p> |
| <ul> |
| <li class="">Python uses markers such as <code>pyfory.Int32</code>, <code>pyfory.Float16</code>, and <code>pyfory.BFloat16</code> when the native |
| Python type does not express the required width.</li> |
| <li class="">Java, Dart, and other languages use annotations or schema metadata where one host type can represent |
| multiple xlang types.</li> |
| <li class="">Reduced-precision <code>float16</code> and <code>bfloat16</code> values and dense arrays use language-specific carriers.</li> |
| <li class=""><code>list<T></code> and dense <code>array<T></code> are distinct schemas. In compatible mode, a direct struct field may |
| adapt between a list and dense bool/numeric array when the element domain is compatible and the |
| actual list contains no unrepresentable null or reference-tracked element.</li> |
| </ul> |
| <p>Use the mapping specification instead of inferring compatibility from similar host-language names.</p> |
| <h3 class="anchor anchorTargetStickyNavbar_Vzrq" id=coordinate-type-identity>Coordinate Type Identity<a href=#coordinate-type-identity class=hash-link aria-label="Direct link to Coordinate Type Identity" title="Direct link to Coordinate Type Identity" translate=no></a></h3> |
| <p>Every peer must register a custom type with either the same numeric ID or the same namespace and type |
| name. Numeric IDs produce smaller metadata; names are easier to coordinate across independently |
| owned services. Do not register one peer by ID and another by name for the same contract.</p> |
| <p>Registration must happen before the first root serialization or deserialization operation. Keep a |
| small contract registry or use generated Fory IDL modules when multiple teams own the peers.</p> |
| <h3 class="anchor anchorTargetStickyNavbar_Vzrq" id=static-and-dynamic-fields>Static and Dynamic Fields<a href=#static-and-dynamic-fields class=hash-link aria-label="Direct link to Static and Dynamic Fields" title="Direct link to Static and Dynamic Fields" translate=no></a></h3> |
| <p>A statically known field uses its declared serializer without writing a concrete type. A |
| dynamic field carries enough type information to select the concrete registered type. Dynamic |
| metadata is needed for interfaces, abstract types, trait objects, and other polymorphic positions; |
| it is unnecessary for primitives and exact final types.</p> |
| <table><thead><tr><th>Language<th>Dynamic field model<tbody><tr><td>Java<td><code>@ForyField(dynamic = ...)</code> controls automatic or forced metadata<tr><td>Python<td><code>pyfory.field(dynamic=...)</code> controls object-field metadata<tr><td>C++<td><code>fory::F(...).dynamic(...)</code> overrides automatic detection<tr><td>Go<td>Interface fields express dynamic values<tr><td>Rust<td>Trait-object carriers express dynamic values</table> |
| <p>Writing dynamic metadata costs space and type-resolution work. Disable it only when the field can |
| never contain another concrete type. Exact annotation and registration examples belong to each |
| language's schema metadata, type registration, and polymorphism pages.</p> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=nullability-and-reference-tracking>Nullability and Reference Tracking<a href=#nullability-and-reference-tracking class=hash-link aria-label="Direct link to Nullability and Reference Tracking" title="Direct link to Nullability and Reference Tracking" translate=no></a></h2> |
| <p>Nullability and reference tracking solve different problems:</p> |
| <table><thead><tr><th>Concern<th>Purpose<tbody><tr><td>Nullability<td>Allows a field or value position to contain no value<tr><td>Reference tracking<td>Preserves repeated object identity and supports object cycles</table> |
| <p>The wire framing is defined by the |
| <a class="" href=/docs/specification/xlang_serialization_spec>xlang serialization specification</a>. Applications |
| should configure the semantic behavior through their language-specific Fory APIs rather than depend |
| on flag values.</p> |
| <h3 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></h3> |
| <p>Xlang struct fields are non-nullable by default. Non-nullable fields are smaller and make required |
| data explicit. Nullable or optional carriers include Java boxed/annotated values, Python |
| <code>Optional[T]</code>, C++ <code>std::optional<T></code>, Go pointers, Rust <code>Option<T></code>, and Scala <code>Option[T]</code>.</p> |
| <p>Keep corresponding fields consistently nullable across peers. In same-schema mode, changing |
| nullability changes the schema and is incompatible. Compatible mode supports the documented |
| nullable and scalar adaptations, but a remote null still cannot be materialized into a local type |
| that has no valid null or missing-value behavior.</p> |
| <h3 class="anchor anchorTargetStickyNavbar_Vzrq" id=shared-and-circular-references>Shared and Circular References<a href=#shared-and-circular-references class=hash-link aria-label="Direct link to Shared and Circular References" title="Direct link to Shared and Circular References" translate=no></a></h3> |
| <p>Enable reference tracking when the graph contains the same object more than once or contains a |
| cycle. Leave it disabled for value-shaped data to avoid identity-table overhead.</p> |
| <div class="language-java codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-java 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"> </span><span class="token import namespace" style=opacity:0.7>org</span><span class="token import namespace punctuation" style=opacity:0.7;color:#393A34>.</span><span class="token import namespace" style=opacity:0.7>apache</span><span class="token import namespace punctuation" style=opacity:0.7;color:#393A34>.</span><span class="token import namespace" style=opacity:0.7>fory</span><span class="token import namespace punctuation" style=opacity:0.7;color:#393A34>.</span><span class="token import class-name">Fory</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>import</span><span class="token plain"> </span><span class="token import namespace" style=opacity:0.7>org</span><span class="token import namespace punctuation" style=opacity:0.7;color:#393A34>.</span><span class="token import namespace" style=opacity:0.7>apache</span><span class="token import namespace punctuation" style=opacity:0.7;color:#393A34>.</span><span class="token import namespace" style=opacity:0.7>fory</span><span class="token import namespace punctuation" style=opacity:0.7;color:#393A34>.</span><span class="token import namespace" style=opacity:0.7>annotation</span><span class="token import namespace punctuation" style=opacity:0.7;color:#393A34>.</span><span class="token import class-name">Ref</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 keyword" style=color:#00009f>public</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>class</span><span class="token plain"> </span><span class="token class-name">Node</span><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"> </span><span class="token keyword" style=color:#00009f>public</span><span class="token plain"> </span><span class="token class-name">String</span><span class="token plain"> value</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 punctuation" style=color:#393A34>@Ref</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>public</span><span class="token plain"> </span><span class="token class-name">Node</span><span class="token plain"> next</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 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 class-name">Node</span><span class="token plain"> first </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>new</span><span class="token plain"> </span><span class="token class-name">Node</span><span class="token punctuation" style=color:#393A34>(</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 class-name">Node</span><span class="token plain"> second </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>new</span><span class="token plain"> </span><span class="token class-name">Node</span><span class="token punctuation" style=color:#393A34>(</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">first</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">next </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> second</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">second</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">next </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> first</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 class-name">Fory</span><span class="token plain"> fory </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> </span><span class="token class-name">Fory</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>withRefTracking</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 punctuation" style=color:#393A34>;</span><br/></div></code></pre></div></div> |
| <p>Global reference tracking enables the reference-tracking mechanism; field metadata selects which positions |
| participate. Common field-level controls are Java and Scala <code>@Ref</code>, Go <code>fory:"ref"</code> tags, Rust |
| <code>#[fory(ref = true)]</code>, and C++ smart-pointer or <code>fory::F().ref()</code> metadata. Consult the language guide |
| because default tracking differs by carrier and language.</p> |
| <p>Reference support also follows the host ownership model. For example, Rust can preserve supported |
| shared-reference carriers, while cycles require representable ownership and weak-reference shapes.</p> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=polymorphism>Polymorphism<a href=#polymorphism class=hash-link aria-label="Direct link to Polymorphism" title="Direct link to Polymorphism" translate=no></a></h2> |
| <p>Xlang polymorphism preserves a value's concrete registered type when its declared field, collection |
| element, or root type is broader. Every receiving peer must:</p> |
| <ol> |
| <li class="">Register the same concrete type identity.</li> |
| <li class="">Provide a compatible field schema for that concrete type.</li> |
| <li class="">Mark or model the position as dynamic when the Fory implementation cannot infer it.</li> |
| <li class="">Use a concrete type that has a portable xlang mapping.</li> |
| </ol> |
| <p>Host-language inheritance alone does not make a type portable. If a shape has no xlang mapping, use |
| native mode for traffic within one Fory implementation family or define a portable model. See the |
| language polymorphism pages for interfaces, trait objects, unions, and generated-code syntax.</p> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=schema-evolution>Schema Evolution<a href=#schema-evolution class=hash-link aria-label="Direct link to Schema Evolution" title="Direct link to Schema Evolution" translate=no></a></h2> |
| <p>Compatible mode is the xlang default. It carries schema metadata so independently deployed readers |
| can tolerate supported field additions, removals, reordering, and documented compatible type |
| adaptations.</p> |
| <p>Keep compatible mode when peers may deploy separately. Select same-schema mode only when every |
| reader and writer uses the same:</p> |
| <ul> |
| <li class="">Type identity and field IDs or names.</li> |
| <li class="">Field types and nested generic shapes.</li> |
| <li class="">Nullability and reference metadata.</li> |
| <li class="">Polymorphic alternatives.</li> |
| </ul> |
| <p>Same-schema mode reduces metadata and payload size, but any mismatch can produce a schema hash or |
| type error. Generated Fory IDL models make exact coordination easier when all peers are released |
| together. Normative compatibility behavior lives in the |
| <a class="" href=/docs/specification/xlang_serialization_spec>xlang serialization specification</a>.</p> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=zero-copy-serialization>Zero-Copy Serialization<a href=#zero-copy-serialization class=hash-link aria-label="Direct link to Zero-Copy Serialization" title="Direct link to Zero-Copy Serialization" translate=no></a></h2> |
| <p>Some Fory implementations can move large binary or numeric buffers out of the main serialized byte stream. This |
| avoids copying those buffers into one contiguous payload.</p> |
| <p>The transport flow is:</p> |
| <ol> |
| <li class="">Serialize the object graph and collect selected buffer objects through a callback.</li> |
| <li class="">Send the main metadata bytes and the collected buffers separately.</li> |
| <li class="">Provide the buffers in the same order during deserialization.</li> |
| </ol> |
| <p>Java:</p> |
| <div class="language-java codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-java codeBlock_bY9V thin-scrollbar" style=color:#393A34;background-color:#f6f8fa><code class=codeBlockLines_e6Vv><div class=token-line style=color:#393A34><span class="token class-name">Collection</span><span class="token generics punctuation" style=color:#393A34><</span><span class="token generics class-name">BufferObject</span><span class="token generics punctuation" style=color:#393A34>></span><span class="token plain"> objects </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>new</span><span class="token plain"> </span><span class="token class-name">ArrayList</span><span class="token generics punctuation" style=color:#393A34><</span><span class="token generics punctuation" style=color:#393A34>></span><span class="token punctuation" style=color:#393A34>(</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 keyword" style=color:#00009f>byte</span><span class="token punctuation" style=color:#393A34>[</span><span class="token punctuation" style=color:#393A34>]</span><span class="token plain"> metadata </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> fory</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>serialize</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">value</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> object </span><span class="token operator" style=color:#393A34>-></span><span class="token plain"> </span><span class="token operator" style=color:#393A34>!</span><span class="token plain">objects</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>add</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">object</span><span class="token punctuation" style=color:#393A34>)</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 class-name">List</span><span class="token generics punctuation" style=color:#393A34><</span><span class="token generics class-name">MemoryBuffer</span><span class="token generics punctuation" style=color:#393A34>></span><span class="token plain"> buffers </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> objects</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>stream</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>map</span><span class="token punctuation" style=color:#393A34>(</span><span class="token class-name">BufferObject</span><span class="token operator" style=color:#393A34>::</span><span class="token function" style=color:#d73a49>toBuffer</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>toList</span><span class="token punctuation" style=color:#393A34>(</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 class-name">Object</span><span class="token plain"> decoded </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> fory</span><span class="token punctuation" style=color:#393A34>.</span><span class="token function" style=color:#d73a49>deserialize</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">metadata</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> buffers</span><span class="token punctuation" style=color:#393A34>)</span><span class="token punctuation" style=color:#393A34>;</span><br/></div></code></pre></div></div> |
| <p>Python:</p> |
| <div class="language-python codeBlockContainer_Ckt0 theme-code-block" style=--prism-color:#393A34;--prism-background-color:#f6f8fa><div class=codeBlockContent_QJqH><pre tabindex=0 class="prism-code language-python 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">objects </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> </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">metadata </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> fory</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">serialize</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">value</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> buffer_callback</span><span class="token operator" style=color:#393A34>=</span><span class="token plain">objects</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">append</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">buffers </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> </span><span class="token punctuation" style=color:#393A34>[</span><span class="token plain">obj</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">to_buffer</span><span class="token punctuation" style=color:#393A34>(</span><span class="token punctuation" style=color:#393A34>)</span><span class="token plain"> </span><span class="token keyword" style=color:#00009f>for</span><span class="token plain"> obj </span><span class="token keyword" style=color:#00009f>in</span><span class="token plain"> objects</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">decoded </span><span class="token operator" style=color:#393A34>=</span><span class="token plain"> fory</span><span class="token punctuation" style=color:#393A34>.</span><span class="token plain">deserialize</span><span class="token punctuation" style=color:#393A34>(</span><span class="token plain">metadata</span><span class="token punctuation" style=color:#393A34>,</span><span class="token plain"> buffers</span><span class="token operator" style=color:#393A34>=</span><span class="token plain">buffers</span><span class="token punctuation" style=color:#393A34>)</span><br/></div></code></pre></div></div> |
| <p>Go exposes the equivalent callback-buffer flow through its serialization and buffer APIs. Use the |
| language guide for the current method names and supported buffer carriers.</p> |
| <p>Out-of-band serialization helps when buffers are large and the transport can send them without an |
| additional copy. For small arrays, callback and multi-buffer transport overhead may cost more than |
| copying. The application owns buffer ordering, lifetime, and transport framing. See |
| <a class="" href=/docs/object-serialization/python/out-of-band>Python Out-of-Band Serialization</a> for Python and NumPy details.</p> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=troubleshooting>Troubleshooting<a href=#troubleshooting class=hash-link aria-label="Direct link to Troubleshooting" title="Direct link to Troubleshooting" translate=no></a></h2> |
| <table><thead><tr><th>Symptom<th>Likely cause<th>Resolution<tbody><tr><td>Type is not registered<td>Registration missing or performed too late<td>Register every custom type before the first root operation<tr><td>Type ID or name mismatch<td>Peers use different identities<td>Use the same numeric ID or the same namespace and type name<tr><td>Integer overflow or float precision loss<td>Host carriers use different numeric widths<td>Follow the type mapping and use explicit width metadata<tr><td>Fields decode incorrectly<td>Field IDs, names, or types differ<td>Align field metadata or regenerate all peers from the same IDL<tr><td>Stack overflow on a cyclic graph<td>Reference tracking is disabled<td>Enable global and field-level reference tracking<tr><td>Shared objects become duplicates<td>The value position does not track references<td>Enable reference tracking for that carrier or field<tr><td>Unsupported host type<td>The type has no portable xlang representation<td>Use a portable model or native mode within one Fory implementation family<tr><td>Schema/hash mismatch<td>Same-schema peers have different schemas<td>Align every peer or restore compatible mode<tr><td>Failure after an upgrade<td>Peers run incompatible protocol versions<td>Align supported Fory versions and review release notes<tr><td>Payload rejected immediately<td>One peer wrote native bytes and another reads xlang<td>Keep all peers on xlang for a cross-language contract</table> |
| <h3 class="anchor anchorTargetStickyNavbar_Vzrq" id=diagnostic-checklist>Diagnostic Checklist<a href=#diagnostic-checklist class=hash-link aria-label="Direct link to Diagnostic Checklist" title="Direct link to Diagnostic Checklist" translate=no></a></h3> |
| <ol> |
| <li class="">Confirm that every peer uses xlang mode and a mutually supported Fory version.</li> |
| <li class="">Compare the registered type identity, field IDs or names, numeric widths, nullability, and |
| reference metadata.</li> |
| <li class="">Reproduce a local round trip in each Fory implementation before testing the cross-language direction.</li> |
| <li class="">Test both directions for every language pair used in production.</li> |
| <li class="">Reduce the value to one type and field, then add fields back until the mismatch appears.</li> |
| <li class="">Inspect the language-specific troubleshooting page for generated-code, platform, or API errors.</li> |
| </ol> |
| <p>When diagnosing binary layout, use the specifications and implementation-specific debug facilities. Do not treat a |
| hex dump or internal flag value as a stable application API.</p> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=language-guides>Language Guides<a href=#language-guides class=hash-link aria-label="Direct link to Language Guides" title="Direct link to Language Guides" translate=no></a></h2> |
| <ul> |
| <li class=""><a class="" href=/docs/object-serialization/java/basic-serialization#cross-language-interoperability>Java</a></li> |
| <li class=""><a class="" href=/docs/object-serialization/python/basic-serialization#cross-language-interoperability>Python</a></li> |
| <li class=""><a class="" href=/docs/object-serialization/cpp/basic-serialization#cross-language-interoperability>C++</a></li> |
| <li class=""><a class="" href=/docs/object-serialization/go/basic-serialization#cross-language-interoperability>Go</a></li> |
| <li class=""><a class="" href=/docs/object-serialization/rust/basic-serialization#cross-language-interoperability>Rust</a></li> |
| <li class=""><a class="" href=/docs/object-serialization/javascript/basic-serialization#cross-language-interoperability>JavaScript/TypeScript</a></li> |
| <li class=""><a class="" href=/docs/object-serialization/csharp/basic-serialization#cross-language-interoperability>C#</a></li> |
| <li class=""><a class="" href=/docs/object-serialization/swift/basic-serialization#cross-language-interoperability>Swift</a></li> |
| <li class=""><a class="" href=/docs/object-serialization/dart/basic-serialization#cross-language-interoperability>Dart</a></li> |
| <li class=""><a class="" href=/docs/object-serialization/scala/basic-serialization#cross-language-interoperability>Scala</a></li> |
| <li class=""><a class="" href=/docs/object-serialization/kotlin/basic-serialization#cross-language-interoperability>Kotlin</a></li> |
| </ul> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=related-documentation>Related Documentation<a href=#related-documentation class=hash-link aria-label="Direct link to Related Documentation" title="Direct link to Related Documentation" translate=no></a></h2> |
| <ul> |
| <li class=""><a class="" href=/docs/specification/xlang_serialization_spec>Xlang Serialization Format</a> — normative wire format</li> |
| <li class=""><a class="" href=/docs/specification/xlang_type_mapping>Xlang Type Mapping</a> — exact host-language carrier mappings</li> |
| <li class=""><a class="" href=/docs/compiler/>Fory IDL and Compiler</a> — schema-first models and code generation</li> |
| <li class=""><a class="" href=/docs/start/>Getting Started</a> — installation and first serialization for each language</li> |
| <li class=""><a class="" href=/docs/row-format/>Row Format</a> — random-access analytical rows for trusted data</li> |
| </ul> |
| <h2 class="anchor anchorTargetStickyNavbar_Vzrq" id=operational-best-practices>Operational Best Practices<a href=#operational-best-practices class=hash-link aria-label="Direct link to Operational Best Practices" title="Direct link to Operational Best Practices" translate=no></a></h2> |
| <ol> |
| <li class="">Coordinate one type identity and field contract across every peer.</li> |
| <li class="">Keep compatible mode unless all readers and writers deploy the same schema together.</li> |
| <li class="">Enable reference tracking only for identity-bearing or cyclic graphs.</li> |
| <li class="">Reuse configured Fory instances instead of rebuilding them for each operation.</li> |
| <li class="">Validate every production language pair in both directions before deployment.</li> |
| <li class="">Prefer Fory IDL once a contract spans many messages, services, or independently owned teams.</li> |
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