docs/guide/rust/xlang-serialization.md

---
title: Xlang Serialization
sidebar_position: 2
id: xlang_serialization
license: |
  Licensed to the Apache Software Foundation (ASF) under one or more
  contributor license agreements.  See the NOTICE file distributed with
  this work for additional information regarding copyright ownership.
  The ASF licenses this file to You under the Apache License, Version 2.0
  (the "License"); you may not use this file except in compliance with
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---

Apache Fory™ supports seamless data exchange across Java, Python, C++, Go,
Rust, JavaScript/TypeScript, C#, Swift, Dart, Scala, and Kotlin.

## Create an Xlang Fory Instance

Rust defaults to xlang mode with compatible schema evolution. Set the mode explicitly in xlang examples:

```rust
use fory::Fory;

// Use xlang mode
let mut fory = Fory::builder().xlang(true).build();

// Register types with consistent IDs across languages
fory.register::<MyStruct>(100)?;

// Or use name-based registration
fory.register_by_name::<MyStruct>("com.example.MyStruct")?;
```

## Type Registration for Xlang

### Register by ID

For fast, compact serialization with consistent IDs across languages:

```rust
let mut fory = Fory::builder().xlang(true).build();

fory.register::<User>(100)?;  // Same ID in Java, Python, etc.
```

### Register by Name

For more flexible type naming:

```rust
fory.register_by_name::<User>("com.example.User")?;
```

## Xlang Example

### Rust (Serializer)

```rust
use fory::Fory;
use fory::ForyStruct;

#[derive(ForyStruct)]
struct Person {
    name: String,
    age: i32,
}

let mut fory = Fory::builder().xlang(true).build();

fory.register::<Person>(100)?;

let person = Person {
    name: "Alice".to_string(),
    age: 30,
};

let bytes = fory.serialize(&person)?;
// bytes can be deserialized by Java, Python, etc.
```

### Java (Deserializer)

```java
import org.apache.fory.*;
import org.apache.fory.config.*;

public class Person {
    public String name;
    public int age;
}

Fory fory = Fory.builder()
    .withXlang(true)
    .withRefTracking(true)
    .build();

fory.register(Person.class, 100);  // Same ID as Rust

Person person = (Person) fory.deserialize(bytesFromRust);
```

### Python (Deserializer)

```python
import pyfory
from dataclasses import dataclass

@dataclass
class Person:
    name: str
    age: pyfory.Int32

fory = pyfory.Fory(xlang=True, ref=True)
fory.register_type(Person, type_id=100)  # Same ID as Rust

person = fory.deserialize(bytes_from_rust)
```

## Type Mapping

See [xlang_type_mapping.md](../../specification/xlang_type_mapping.md) for complete type mapping across languages.

### Common Type Mappings

| Rust            | Java           | Python          |
| --------------- | -------------- | --------------- |
| `i32`           | `int`          | `int32`         |
| `i64`           | `long`         | `int64`         |
| `f32`           | `float`        | `float32`       |
| `f64`           | `double`       | `float64`       |
| `Float16`       | `Float16`      | `float16`       |
| `BFloat16`      | `BFloat16`     | `bfloat16`      |
| `String`        | `String`       | `str`           |
| `Vec<T>`        | `List<T>`      | `List[T]`       |
| `Vec<Float16>`  | `Float16List`  | `Float16Array`  |
| `Vec<BFloat16>` | `BFloat16List` | `BFloat16Array` |
| `[Float16; N]`  | `Float16List`  | `Float16Array`  |
| `[BFloat16; N]` | `BFloat16List` | `BFloat16Array` |
| `HashMap<K,V>`  | `Map<K,V>`     | `Dict[K,V]`     |
| `Option<T>`     | nullable `T`   | `Optional[T]`   |

### Lists and Dense Arrays

Rust `Vec<T>` maps to Fory `list<T>` by default for manual structs. Use an
explicit array field attribute when the schema is dense `array<T>`.

| Fory schema       | Rust carrier and metadata      |
| ----------------- | ------------------------------ |
| `list<int32>`     | `Vec<i32>`                     |
| `array<bool>`     | `#[fory(array)] Vec<bool>`     |
| `array<int8>`     | `#[fory(array)] Vec<i8>`       |
| `array<int16>`    | `#[fory(array)] Vec<i16>`      |
| `array<int32>`    | `#[fory(array)] Vec<i32>`      |
| `array<int64>`    | `#[fory(array)] Vec<i64>`      |
| `array<uint8>`    | `#[fory(array)] Vec<u8>`       |
| `array<uint16>`   | `#[fory(array)] Vec<u16>`      |
| `array<uint32>`   | `#[fory(array)] Vec<u32>`      |
| `array<uint64>`   | `#[fory(array)] Vec<u64>`      |
| `array<float16>`  | `#[fory(array)] Vec<Float16>`  |
| `array<bfloat16>` | `#[fory(array)] Vec<BFloat16>` |
| `array<float32>`  | `#[fory(array)] Vec<f32>`      |
| `array<float64>`  | `#[fory(array)] Vec<f64>`      |

## Best Practices

1. **Use consistent type IDs** across all languages
2. **Keep compatible mode** for schema evolution
3. **Register all types** before serialization
4. **Test cross-language** compatibility during development

## See Also

- [Xlang Serialization Specification](../../specification/xlang_serialization_spec.md)
- [Type Mapping Reference](../../specification/xlang_type_mapping.md)
- [Java Xlang Serialization Guide](../java/xlang-serialization.md)
- [Python Xlang Serialization Guide](../python/xlang-serialization.md)

## Related Topics

- [Configuration](configuration.md) - xlang mode configuration
- [Schema Evolution](schema-evolution.md) - Compatible mode
- [Type Registration](type-registration.md) - Registration methods