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title: Troubleshooting sidebar_position: 12 id: troubleshooting 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.

Symptom	Likely cause and action
ForyJsonException while parsing	Invalid JSON grammar, type mismatch, unsupported mapping, depth or graph-memory violation, validator failure, or trailing content
InsecureException	Fory's disallow list or the configured JsonTypeChecker rejected a class
IllegalArgumentException from a builder	Check the configured depth, graph-memory, concurrency, retained-buffer, and cached-field-name limits
Declared write is rejected	The value is not assignable to the declared type, the type contains a wildcard/type variable, or null was supplied for a primitive
Immutable value is not populated	Use a record, a valid JsonCreator, or an exact custom codec
JsonValue read fails	Add one plain String JsonCreator, or register an exact custom codec
Raw JSON output is invalid	Supply exactly one trusted, complete JSON value to the JsonRawValue property
Ordinary object cannot be constructed	Add a usable no-argument constructor, use a record or JsonCreator, or register a custom codec; Android and GraalVM native image are stricter
Ordinary accessor annotation fails	The method is not an eligible public JavaBean accessor, or field mode is enabled
Any annotation fails	Use exactly one field-backed form or one valid method-backed pair with resolved Map<String, V> types; method annotations require non-field mode
Codec annotation fails	Resolve same-node or hierarchy conflicts, remove a hidden nested override, or use a public no-argument codec class
Subtype is rejected	The base is not declared on the write, the runtime class is not an exact table entry, or the input wire shape differs from the configured inclusion
Collection cannot be read	Target a supported interface/common implementation or register a custom codec
OutputStream write fails	The underlying IOException is wrapped as the cause of ForyJsonException
Kotlin null or missing member fails	Check the exact jsonTypeRef, constructor default, and nullable occurrence; null does not request a compiler default
Raw/star/projected Kotlin generic fails	Supply a complete jsonTypeRef<T>(); in and star projections cannot reconstruct one exact schema
Unsupported Kotlin metadata	Compile the model with a supported Kotlin 2.3 compiler and ensure its validated JVM members match the metadata
Kotlin model fails after Android shrinking	Apply KSP; for an exact Mixin, use it when either its source or target is Kotlin, and verify that the generated rules are packaged
Kotlin model is absent in Native Image	Install ForyJsonKotlin from a reachable ForyJsonProvider, enable code generation, and make the exact binding reachable from that configuration

Fory JSON mapping, syntax, codec, depth, graph-memory, validator, and output failures use ForyJsonException. User codec code may still throw its own runtime exception. Creator and validator failures other than Error are wrapped with their original cause.