使用 BeanDeserializerModifier 使用自定义反序列化程序是个好主意。您只需要改进反序列化程序实现。在您的示例中，问题在于这些行：

final Object deserialized = deserializer.deserialize(p, ctxt); //1.
ObjectCodec codec = p.getCodec(); //2.
JsonNode node = codec.readTree(p); //3.

线路 1. 阅读 JSON Object . 排队 2. 以及 3. 你想创建一个 JsonNode 但是空的 JSON Object 已经排成一行了 1. . 接下来的两行将尝试读取负载的其余部分 JsonNode . Jackson 默认使用 BeanDeserializer 反序列化正则表达式 POJO 班级。我们可以扩展这个类并提供自己的实现。在版本中
2.10.1 deserialise 方法如下所示：

@Override
public Object deserialize(JsonParser p, DeserializationContext ctxt) throws IOException
{
    // common case first
    if (p.isExpectedStartObjectToken()) {
        if (_vanillaProcessing) {
            return vanillaDeserialize(p, ctxt, p.nextToken());
        }
        // 23-Sep-2015, tatu: This is wrong at some many levels, but for now... it is
        //    what it is, including "expected behavior".
        p.nextToken();
        if (_objectIdReader != null) {
            return deserializeWithObjectId(p, ctxt);
        }
        return deserializeFromObject(p, ctxt);
    }
    return _deserializeOther(p, ctxt, p.getCurrentToken());
}

在大多数情况下，不需要特殊治疗 vanillaDeserialize 方法将被调用。我们来看看：

private final Object vanillaDeserialize(JsonParser p, DeserializationContext ctxt, JsonToken t) throws IOException {
    final Object bean = _valueInstantiator.createUsingDefault(ctxt);
    // [databind#631]: Assign current value, to be accessible by custom serializers
    p.setCurrentValue(bean);
    if (p.hasTokenId(JsonTokenId.ID_FIELD_NAME)) {
        String propName = p.getCurrentName();
        do {
            p.nextToken();
            SettableBeanProperty prop = _beanProperties.find(propName);

            if (prop != null) { // normal case
                try {
                    prop.deserializeAndSet(p, ctxt, bean);
                } catch (Exception e) {
                    wrapAndThrow(e, bean, propName, ctxt);
                }
                continue;
            }
            handleUnknownVanilla(p, ctxt, bean, propName);
        } while ((propName = p.nextFieldName()) != null);
    }
    return bean;
}

正如你所看到的，它几乎做了我们想要的一切，除了它创建了新的对象，即使是空的 JSON Object . 它在创建新对象之后检查字段是否存在。一行太远了。不幸的是，这个方法是私有的，我们不能重写它。我们把它复制到我们班上，再修改一下：

class EmptyObjectIsNullBeanDeserializer extends BeanDeserializer {

    EmptyObjectIsNullBeanDeserializer(BeanDeserializerBase src) {
        super(src);
    }

    @Override
    public Object deserialize(JsonParser p, DeserializationContext ctxt) throws IOException {
        if (_vanillaProcessing) {
            return vanillaDeserialize(p, ctxt);
        }

        return super.deserialize(p, ctxt);
    }

    private Object vanillaDeserialize(JsonParser p, DeserializationContext ctxt) throws IOException {
        p.nextToken();
        if (p.hasTokenId(JsonTokenId.ID_FIELD_NAME)) {
            final Object bean = _valueInstantiator.createUsingDefault(ctxt);
            // [databind#631]: Assign current value, to be accessible by custom serializers
            p.setCurrentValue(bean);
            String propName = p.getCurrentName();
            do {
                p.nextToken();
                SettableBeanProperty prop = _beanProperties.find(propName);

                if (prop != null) { // normal case
                    try {
                        prop.deserializeAndSet(p, ctxt, bean);
                    } catch (Exception e) {
                        wrapAndThrow(e, bean, propName, ctxt);
                    }
                    continue;
                }
                handleUnknownVanilla(p, ctxt, bean, propName);
            } while ((propName = p.nextFieldName()) != null);
            return bean;
        }
        return null;
    }
}

您可以按以下方式注册：

class EmptyObjectIsNullBeanDeserializerModifier extends BeanDeserializerModifier {
    @Override
    public JsonDeserializer<?> modifyDeserializer(DeserializationConfig config, BeanDescription beanDesc, JsonDeserializer<?> deserializer) {
        if (beanDesc.getBeanClass() == Car.class) { //TODO: change this condition
            return new EmptyObjectIsNullBeanDeserializer((BeanDeserializerBase) deserializer);
        }
        return super.modifyDeserializer(config, beanDesc, deserializer);
    }
}

简单 POC :

import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonTokenId;
import com.fasterxml.jackson.databind.BeanDescription;
import com.fasterxml.jackson.databind.DeserializationConfig;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonDeserializer;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.deser.BeanDeserializer;
import com.fasterxml.jackson.databind.deser.BeanDeserializerBase;
import com.fasterxml.jackson.databind.deser.BeanDeserializerModifier;
import com.fasterxml.jackson.databind.deser.SettableBeanProperty;
import com.fasterxml.jackson.databind.module.SimpleModule;
import lombok.Data;

import java.io.File;
import java.io.IOException;

public class EmptyObjectIsNullApp {

    public static void main(String[] args) throws IOException {
        File jsonFile = new File("./resource/test.json").getAbsoluteFile();

        SimpleModule emptyObjectIsNullModule = new SimpleModule();
        emptyObjectIsNullModule.setDeserializerModifier(new EmptyObjectIsNullBeanDeserializerModifier());

        ObjectMapper mapper = new ObjectMapper();
        mapper.registerModule(emptyObjectIsNullModule);

        Wrapper wrapper = mapper.readValue(jsonFile, Wrapper.class);
        System.out.println(wrapper);
    }
}

@Data
class Wrapper {
    private Car car;
}

@Data
class Car {
    private int id;
}

对于“空对象” JSON 有效载荷：

{
  "car": {}
}

以上代码打印：

Wrapper(car=null)

为了 JSON 带某些字段的有效负载：

{
  "car": {
    "id": 1
  }
}

以上代码打印：

Wrapper(car=Car(id=1))