integration.md

title	Integration
sidebar_position	13
id	integration
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 the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Spring Fory

spring-fory provides Spring MVC message converters, Spring WebFlux codecs, and Spring Boot auto-configuration starters for Fory JSON. It supports ordinary JSON request and response bodies, with streaming JSON and NDJSON support in WebFlux.

See the project's installation and usage guide to select the adapter or starter matching your Spring version and configure your application.

Kotlin integration

Use jsonTypeRef<Any?>(kType) when a framework supplies a Kotlin KType at runtime and the callback cannot use a reified type argument. The supplied KType determines the complete JSON type, including nested generic arguments and nullability. Any? is only the callback's static view of the value; it does not replace the supplied type with a dynamic JSON schema.

Obtaining a KType from a Kotlin function or a Java Method requires the application's kotlin-reflect dependency. Match its version to the application's Kotlin version:

dependencies {
  implementation(kotlin("reflect"))
}

For example, discover and retain a controller method's response type:

import java.io.OutputStream
import kotlin.reflect.jvm.kotlinFunction
import org.apache.fory.json.kotlin.ForyJsonKotlin
import org.apache.fory.json.kotlin.jsonTypeRef

data class Employee(val id: Long, val name: String)
data class Response<T>(val flag: Boolean, val data: T? = null, val msg: String? = null)

class EmployeeController {
  fun employees(): Response<List<Employee>> =
    Response(true, listOf(Employee(1, "Alice")))
}

val json = ForyJsonKotlin.builder().build()
val method = EmployeeController::class.java.getMethod("employees")
val responseType = jsonTypeRef<Any?>(requireNotNull(method.kotlinFunction).returnType)

fun writeResponse(value: Any?, output: OutputStream) {
  json.writeJsonTo(value, responseType, output)
}

fun readResponse(bytes: ByteArray): Any? = json.fromJson(bytes, responseType)

Discover each declared type once and reuse its token. For request bodies, obtain the corresponding Kotlin value parameter's KType. A method with unresolved type parameters still needs its concrete type arguments before conversion; star projections and contravariant projections remain unsupported. If you select a static type more specific than Any?, the caller must ensure it matches the supplied KType.

For Spring MVC, retain the controller's Kotlin declaration when adapting the request or response to a converter. A SmartHttpMessageConverter can receive application-provided read/write hints containing that KType or its Fory type token. When an HTTP wrapper such as ResponseEntity<Response<List<Employee>>> is present, select the body type Response<List<Employee>> before constructing the token.

An AbstractHttpMessageConverter callback that supplies only the runtime object loses generic arguments. AbstractGenericHttpMessageConverter preserves Java generics, but TypeRef.of(javaType) does not restore Kotlin nullability. Neither a Java Type nor the runtime value alone can recover the full Kotlin declaration. Use jsonTypeRef(kType) after obtaining that declaration; this API does not automatically install a Spring converter.

Token-level reading and writing

Frameworks that bring their own (de)serializers, for example generated at compile time, can use Fory JSON's UTF-8 reader and writer directly instead of its object mapping. readUtf8 accepts a Function<Utf8JsonReader, R> and returns its result. writeUtf8 accepts a Consumer<Utf8JsonWriter> and returns the written bytes:

ForyJson json = ForyJson.builder().build();

byte[] bytes =
    json.writeUtf8(
        writer -> {
          writer.writeObjectStart();
          writer.writeFieldName("id");
          writer.writeInt(7);
          writer.writeObjectEnd();
        });

int id =
    json.readUtf8(
        bytes,
        0,
        bytes.length,
        reader -> {
          reader.expectNextToken('{');
          String name = reader.readFieldName(); // "id"
          reader.expect(':');
          int value = reader.readInt();
          reader.expectNextToken('}');
          return value;
        });

Each operation must synchronously read or write exactly one JSON value. The reader and writer are only valid inside the operation. readUtf8 rejects trailing non-whitespace content after the operation returns.

Token methods such as expectNextToken do not track nesting or allocation on their own. Like a custom codec, an external deserializer that reads untrusted input should call reader.enterDepth() / reader.exitDepth() around each object or array and reader.reserveGraphMemory(bytes) before allocating containers, so the instance's maxDepth and graph-memory limits apply; see Security. Unchecked exceptions thrown by the operation propagate unchanged. Integration code must wrap checked exceptions, for example by wrapping an IOException in an UncheckedIOException. Like the other root APIs, these methods are not reentrant on the same ForyJson instance.