自定义Jackson的反序列化Deserializer

import lombok.Data;

@Data
public class User {
    private String name;
    private Integer age;
    private boolean isAdult;
}

自定义Deserializer

import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.*;
import com.fasterxml.jackson.databind.deser.BeanDeserializerModifier;
import com.fasterxml.jackson.databind.deser.ResolvableDeserializer;
import com.fasterxml.jackson.databind.deser.std.StdDeserializer;
import com.fasterxml.jackson.databind.module.SimpleModule;

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

public class UserEventDeserializer extends StdDeserializer<User> implements ResolvableDeserializer {
    private static final long serialVersionUID = 7923585097068641765L;

    private final JsonDeserializer<?> defaultDeserializer;

    public UserEventDeserializer(JsonDeserializer<?> defaultDeserializer) {
        super(User.class);
        this.defaultDeserializer = defaultDeserializer;
    }

    @Override
    public User deserialize(JsonParser jp, DeserializationContext ctxt)
            throws IOException, JsonProcessingException {
        User deserializedUser = (User) defaultDeserializer.deserialize(jp, ctxt);

        // 业务逻辑代码，如果小于18则未成年
        if (deserializedUser.getAge() < 18) {
            deserializedUser.setAdult(false);
        } else {
            deserializedUser.setAdult(true);
        }
        return deserializedUser;
    }

    // for some reason you have to implement ResolvableDeserializer when modifying BeanDeserializer
    // otherwise deserializing throws JsonMappingException??
    @Override
    public void resolve(DeserializationContext ctxt) throws JsonMappingException {
        ((ResolvableDeserializer) defaultDeserializer).resolve(ctxt);
    }


    public static void main(String[] args) throws IOException {
        SimpleModule module = new SimpleModule();
        module.setDeserializerModifier(new BeanDeserializerModifier() {
            @Override
            public JsonDeserializer<?> modifyDeserializer(DeserializationConfig config, BeanDescription beanDesc, JsonDeserializer<?> deserializer) {
                if (beanDesc.getBeanClass() == User.class) {
                    return new UserEventDeserializer(deserializer);
                }
                return deserializer;
            }
        });


        ObjectMapper mapper = new ObjectMapper();
        mapper.registerModule(module);
        User user = mapper.readValue("{\"name\":\"张三\",\"age\":12}", User.class);
        System.out.println(user);

    }
}