[QUESTION] fastjson2和fastjson抽象类反序列化默认行为不一致

[rock-byte]

问题描述

fastjson2和fastjson抽象类反序列化默认行为不一致，fastjson2在反序列化抽象类时会抛出异常，fastjson会跳过该类。并没有找到配置项控制该行为。

重现步骤

public static abstract class Foo {

        private String value;
    }

    public static void main(String[] args) {
        String jsonString = "{\"value\":\"bar\"}";
        com.alibaba.fastjson2.JSON.config(JSONReader.Feature.FieldBased);
        Foo fooBefore = com.alibaba.fastjson.JSON.parseObject(jsonString, Foo.class);
        System.out.println(fooBefore);
        Foo foo = com.alibaba.fastjson2.JSON.parseObject(jsonString, Foo.class);
        System.out.println(foo);
    }

结果

null
Exception in thread "main" com.alibaba.fastjson2.JSONException: create instance error, class Test$Foo
	at com.alibaba.fastjson2.reader.ObjectReaderAdapter.createInstance(ObjectReaderAdapter.java:411)
	at com.alibaba.fastjson2.reader.ObjectReaderBean.readObject(ObjectReaderBean.java:386)
	at com.alibaba.fastjson2.JSON.parseObject(JSON.java:864)
	at Test.main(Test.java:19)
Caused by: java.lang.InstantiationException
	at sun.reflect.InstantiationExceptionConstructorAccessorImpl.newInstance(InstantiationExceptionConstructorAccessorImpl.java:48)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
	at com.alibaba.fastjson2.reader.ObjectReaderAdapter.createInstance(ObjectReaderAdapter.java:405)
	... 3 more

期待结果

fastjson2和fastjson对于抽象类反序列化默认行为一致，或至少提供配置项控制。

[amabilee]

Have you tried instead of directly deserializing the abstract class, deserialize a concrete subclass that extends the abstract class?
This way, you can avoid the exception thrown by fastjson2.