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title Android
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id android
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.

Fory JSON supports ordinary classes on Android API level 26 and later through the regular fory-json artifact. Runtime JSON code generation and asynchronous compilation are disabled automatically, so ForyJson.builder().build() uses the interpreted object mapper.

Kotlin applications use the ordinary fory-json-kotlin runtime. KSP is needed when R8 or ProGuard can rename or remove Kotlin model members or when a Kotlin-source Mixin adds inferred JsonSubTypes to a Java sealed target.

Installation and Codec Model

Add Fory JSON to the application:

dependencies {
  implementation("org.apache.fory:fory-json:${foryVersion}")
}

For Kotlin, apply Kotlin 2.3.20 and add the Kotlin JSON runtime:

plugins {
  kotlin("android") version "2.3.20"
}

dependencies {
  implementation("org.apache.fory:fory-json-kotlin:${foryVersion}")
}

If the application enables R8 or ProGuard, or if a Kotlin-source Mixin adds inferred JsonSubTypes to a Java sealed target, also apply KSP 2.3.8:

plugins {
  id("com.google.devtools.ksp") version "2.3.8"
}

dependencies {
  ksp("org.apache.fory:fory-json-kotlin-ksp:${foryVersion}")
}

Create the runtime with ForyJsonKotlin.builder(). For a minified build, annotate every required Kotlin source model with @JsonType. For a third-party Kotlin target, declare a source-owned exact @JsonMixin instead. If a Kotlin-source Mixin adds inferred JsonSubTypes to a Java sealed target, also apply fory-annotation-processor and compile on JDK 17 or newer.

Custom Codecs

@JsonCodec has the same declaration behavior on Android and the JVM. It supports complete values, direct collection and array elements, Optional and AtomicReference contents, Map keys and values, ordinary getters, setter value parameters, and JsonCreator parameters:

import java.util.List;
import org.apache.fory.json.annotation.JsonCodec;

public final class Invoice {
  @JsonCodec(elementCodec = MoneyCodec.class)
  public List<Money> items;
  private Money primary;

  public void setPrimary(@JsonCodec(MoneyCodec.class) Money primary) {
    this.primary = primary;
  }

  public Invoice() {}
}

Child codecs act on one direct level only. For example, elementCodec on Money[][] handles each Money[], and elementCodec on AtomicReferenceArray<Money> handles each Money. Use a complete value codec when deeper custom behavior is required.

Java Generated Access and R8 Rules

Add the annotation processor and mark application object models with JsonType to generate direct field, getter, setter, Record constructor, JsonCreator, and JsonValidator operations together with exact R8 rules:

dependencies {
  annotationProcessor("org.apache.fory:fory-annotation-processor:${foryVersion}")
}
import org.apache.fory.json.annotation.JsonType;
import org.apache.fory.json.annotation.JsonValidator;

@JsonType
public final class Invoice {
  public long total;

  @JsonValidator
  public void validate() {
    if (total < 0) {
      throw new IllegalArgumentException("total must not be negative");
    }
  }
}

Mixins

The same processor supports Fory JSON Mixins. A Mixin declares one exact target and is registered on the ForyJson builder that should use it:

import org.apache.fory.json.ForyJson;
import org.apache.fory.json.annotation.JsonBase64;
import org.apache.fory.json.annotation.JsonMixin;

@JsonMixin(target = ThirdPartyInvoice.class)
public abstract class ThirdPartyInvoiceMixin {
  @JsonBase64 byte[] signature;
}

ForyJson json =
    ForyJson.builder().registerMixin(ThirdPartyInvoiceMixin.class).build();

Compile a non-empty Java-source Mixin for a Java target with fory-annotation-processor. The registered Mixin remains scoped to its exact target. Registered codecs, effective type codecs, and built-in mappings keep their normal codec-selection precedence.

A Mixin may place JsonValidator on a public abstract zero-argument void method that exactly matches a public target method. The target does not need JsonType solely for a Mixin validator.

The target does not need JsonType merely because it has a Mixin. If the target also uses JsonType, the registered Mixin still defines the effective annotations for that ForyJson instance.

Only one source is enabled for an exact target in one built ForyJson instance. A later registration for that target replaces an earlier registration on the builder, and build() snapshots the selected mapping.

Use the Fory processors instead of broad package keep rules. A Java-only Mixin pair requires fory-annotation-processor; a pair involving Kotlin requires fory-json-kotlin-ksp. A Kotlin-source Mixin that adds inferred JsonSubTypes to a Java sealed target requires both and must be compiled on JDK 17 or newer.

Reflection-Based Models

Ordinary non-Record classes that omit JsonType can supply equivalent exact rules themselves unless they declare JsonValidator. Direct validators require JsonType and fory-annotation-processor; manual reflection rules are not sufficient. Retain every model constructor, field, method, generic signature, declaration annotation, and parameter annotation used by Fory JSON, plus the public no-argument constructor of every annotation-selected codec. For a model without a validator:

-keepattributes Signature,RuntimeVisibleAnnotations,RuntimeVisibleParameterAnnotations
-keepattributes AnnotationDefault,MethodParameters,InnerClasses,EnclosingMethod
-keep,allowoptimization class com.example.Invoice {
  public <init>();
  public java.util.List items;
  public void setPrimary(com.example.Money);
}
-keep,allowoptimization,allowobfuscation class com.example.MoneyCodec {
  public <init>();
}

The same exact-rule approach supports every JsonCodec member; it is not limited to complete-value codecs. JsonType is not required for codec selection on an ordinary class.

This reflection-based section applies to Java models. Kotlin models use the Kotlin JSON module. For a minified Android build, apply KSP instead of writing broad package keep rules.

Java @JsonType models support effective JsonValidator, JsonValue, JsonRawValue, JsonBase64, and JsonFormat annotations. Without @JsonType, those annotations still work through reflection, but a release-minified application must keep the exact annotated members, annotation attributes, and codec constructor itself. A JsonValue method may use a non-JavaBean name, so its manual rule must name that method explicitly.

Kotlin models use the same effective annotations. Enable KSP for minified builds. JsonFormat keeps the same direct-field and one-wrapper-level behavior as on the JVM, including timezone for Instant, ZonedDateTime, and OffsetDateTime.

Android supports inferred JsonSubTypes for Java and Kotlin sealed hierarchies. Java sealed inference requires fory-annotation-processor and JDK 17 or newer. Kotlin models in minified builds require fory-json-kotlin-ksp. For a Kotlin-source Mixin that adds inferred JsonSubTypes to a Java sealed target, apply both processors even when shrinking is disabled. Only the sealed hierarchy is considered; package and classpath subtype scanning are not supported.

Android Fory JSON requires a retained no-argument constructor for an ordinary mutable class; it may be non-public when Android reflection can make it accessible. JsonCreator constructor-backed classes follow the normal creator rules instead. Retain every field and method used for reflection, or use an application codec when a model cannot satisfy those requirements. JsonUnwrapped supports mutable classes, creator-backed classes, and Records through their normal property and construction paths. Apply the normal JsonType requirements to the containing model and every unwrapped child. In a minified Kotlin build, annotate each required model and enable KSP.

Records

Android-desugared Records require either a direct @JsonType declaration or an exact @JsonMixin processed by fory-annotation-processor. Manual R8 rules alone are insufficient because Android does not provide the Java Record reflection APIs. This also applies to a Record whose complete representation is a JsonValue String. Every Record in a JsonUnwrapped path needs its own direct JsonType declaration or processed exact JsonMixin. Child codecs act on one level exactly as they do on the JVM; use a complete value codec for deeper nested behavior.