Registered factory cannot tell a field from the root of the call

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@mohitjoshi-hey 已经在做这个了。

开始于 2026年10月16日。

  • #4186 来自 @mohitjoshi-hey —— 未关闭

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4/5
预计耗时
1-2 天
新手友好度
48/100
Issue 类型
缺陷
描述清晰度
描述清楚
活跃度
活跃
技术栈
java
领域
backend

调研方向

Start at ModuleContext.registerCodecFactory and trace how Fory invokes and caches codec factory answers during root serialization, field serialization, and deserialization. Use the four cases in the reproducer to check whether the factory can distinguish a root value from a field; done means the position is identifiable and the expected behavior is covered by tests. The issue does not name test or implementation files.

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描述

bug
Search before asking
  • I had searched in the issues and found no similar issues.
Version

1.7.7

Component(s)

Java

Minimal reproduce step

ModuleContext.registerCodecFactory is the correct method for an application to supply a codec. It
would also let an application work around https://github.com/apache/fory/issues/4168: a factory that claims the concrete declared
type could write and read the subclass itself.

It cannot do that. Fory asks the factory about the class at the root of its own call and about a field
of that class, and the two questions are not different. Fory also caches the answer for each type, so
the first answer is permanent.

import org.apache.fory.json.*;
import org.apache.fory.json.codec.JsonValueCodec;
import org.apache.fory.json.reader.*;
import org.apache.fory.json.resolver.JsonTypeResolver;
import org.apache.fory.json.writer.*;
import org.apache.fory.reflect.TypeRef;

import java.util.ArrayList;
import java.util.List;

public class RootAndFieldAlike {

    public static class Pet { public String name = "rex"; public Pet() { } }

    public static class Owner { public Pet pet = new Pet(); public Owner() { } }

    static List<String> questions = new ArrayList<>();

    /** a new instance each time, so a cached codec cannot hide a question */
    static ForyJson fresh() {
        questions = new ArrayList<>();
        ForyJsonModule module = ctx -> ctx.registerCodecFactory(
                (TypeRef<?> type, JsonTypeResolver resolver, boolean runtimeType) -> {
                    if (type.getRawType() == Pet.class) {
                        questions.add("Pet, runtimeType=" + runtimeType);
                    }
                    return null;
                });
        return ForyJson.builder().withFieldMode(true).withModule(module).build();
    }

    public static void main(String[] args) {
        ForyJson a = fresh();
        a.toJsonBytes(new Owner());
        print("a Pet held by a field of Owner", questions);

        ForyJson b = fresh();
        b.toJsonBytes(new Pet());
        print("a Pet as the root of the call", questions);

        ForyJson c = fresh();
        c.fromJson("{\"pet\":{\"name\":\"rex\"}}".getBytes(), Owner.class);
        print("reading a Pet held by a field", questions);

        ForyJson d = fresh();
        d.fromJson("{\"name\":\"rex\"}".getBytes(), Pet.class);
        print("reading a Pet as the root", questions);
    }

    static void print(String what, List<String> asked) {
        System.out.println(what + ":");
        if (asked.isEmpty()) {
            System.out.println("   never asked");
            return;
        }
        for (String q : asked) {
            System.out.println("   " + q);
        }
    }
}
What did you expect to see?

A question that says which of the two positions the type is in. The runtimeType flag looks like that
question, so we expected true for the root of the call and false for a field.

What did you see instead?

runtimeType=false for a field and for the root. The root is asked twice, once with each value, so
no value of the flag means "this is a field".

Anything Else?

No response

Are you willing to submit a PR?
  • I'm willing to submit a PR!
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