Thank you for suggesting this fix.

I am not quite sure I understand what problem it would solve -- would it be possible to show a test case?
A unit test would be needed to verify that the fix works, too, and would show the problem to me.

when I receive json data from http request body by SpringMVC Controller,

Controller below

    @PostMapping("add/body")
    public BaseResponseVO saveBody(@Valid @RequestBody UserParam userParam) {
        log.debug("\n====>当前添加的用户信息是{}", userParam);
        UserModel userModel = userService.add(userParam);
        return BaseResponseVO.success(userModel);
    }

the Controller need to deserialize the json data to POJO. there is a Field which is Enum type defined by myself in the POJO.

POJO below

@Data
public class UserParam {
    @NotBlank(message = "name不能为空")
    String name;
    @NotNull(message = "gender为1或者2")
    GenderEnum gender;
    @NotNull(message = "age不能为空")
    Integer age;
}

first , I need to defined a interface which would be implements by Enum.like this

package hxy.dream.entity.enums;

/**
 * The interface Enumerator.
 */
// 如果发现注入的bean无法解决json序列化问题，那么可以加上这个注解
//@JsonFormat(shape = JsonFormat.Shape.OBJECT)
public interface BaseEnum {
    /**
     * Code integer.
     *
     * @return the integer
     */
    Integer code();

    /**
     * Description string.
     *
     * @return the string
     */
    String description();

}

so that I defined a Eume name GenderEnum.java which implements BaseEnum.

public enum GenderEnum implements BaseEnum {
    BOY(100, "男"), GIRL(200, "女"),UNKNOWN(0, "未知");
    @EnumValue//标记数据库存的值是code
    private final Integer code;
    private final String description;

    GenderEnum(int code, String description) {
        this.code = code;
        this.description = description;
    }

    @Override
    public Integer code() {
        return code;
    }

    @Override
    public String description() {
        return description;
    }

maybe there are many Enum implement BaseEnum will be defined in project , so I hope there is a JsonDeserializer<BaseEnum> to deserialize the Enum which implement BaseEnum. not only GenderEnum.

actually, I found com.fasterxml.jackson.databind.deser.BasicDeserializerFactory#createEnumDeserializer can't find custom Enum deserializer by super interface which Enum implemented.

@Slf4j
@Configuration
public class BeanConfig {
    @Bean
    public Jackson2ObjectMapperBuilderCustomizer enumCustomizer() {
//        将枚举转成json返回给前端
        return jacksonObjectMapperBuilder -> {
//            自定义序列化器注入
            Map<Class<?>, JsonSerializer<?>> serializers = new LinkedHashMap<>();
            serializers.put(BaseEnum.class, new BaseEnumSerializer());
            serializers.put(Date.class, new DateJsonSerializer());
            jacksonObjectMapperBuilder.serializersByType(serializers);

//            自定义反序列化器注入
            Map<Class<?>, JsonDeserializer<?>> deserializers = new LinkedHashMap<>();
            deserializers.put(BaseEnum.class, new BaseEnumDeserializer());
//            deserializers.put(GenderEnum.class, new BaseEnumDeserializer());
            jacksonObjectMapperBuilder.deserializersByType(deserializers);

        };
    }
}

in current jackson code ,if I want to deserialize GenderEnum ,I have to register BaseEnumDeserializer by GenderEnum.class.like this

deserializers.put(GenderEnum.class, new BaseEnumDeserializer());

if there are many Enums implements BaseEnum,I have to register all in deserializers map. I think it is so terrible
so I add code in jackson source below. I hope it can help me to find customer BaseEnumDeserializer by super interface not only Enum itself.

//            这里应该需要继续查找当前类的父接口
            List<JavaType> interfaces = type.getInterfaces();
//            再次查找自定义的序列化器
            for (JavaType javaType : interfaces) {
                Class<?> rawClass = javaType.getRawClass();
                deser = _findCustomEnumDeserializer(rawClass, config, beanDesc);
                if (deser != null) {
                    return deser;
                }
            }

if you have time and interesting to run my project https://github.com/aohanhongzhi/SpringCloud-multiple-gradle , it's my honor to show the feature to complete Enum deserialize by BaseEnumDeserializer.

@aohanhongzhi First of all, thank you for full explanation -- this makes sense.

Now, the challenge here is that deserializer registration relies on class(es) from Spring framework, Jackson2ObjectMapperBuilderCustomizer (and/or builders), and I am not sure which mechanism that uses from jackson-databind. Calls to find custom deserializers go through com.fasterxml.jackson.databind.deser.Deserializers implementations that are usually registered using Jackson Modules. Method getting called for Enum type would be findEnumDeserializer() (if nominal type is an Enum subtype), but to findBeanDeserializer() if nominal type is not Enum (or one of other "well-known" types).

So it is up to Deserializers implementation to find implementation: it definitely should be possible to create enum deserializers that you want, and get it registered for all subtypes. But the question is how to achieve that through Spring.

@cowtowncoder In the current version, how can I implement the enumeration deserialization I want

@aohanhongzhi First you need to ensure your deserializer is used by Spring: I do not know exactly how that is to be done.
Once that works I can help with problems of deserializer itself, if any.

But as I said, you need to somehow register Deserializers implementation to ObjectMapper that Spring uses: it has methods:

• findEnumDeserializer() if declared type (in class definition, for property) is an Enum
• findBeanDeserializer() if declared types is not one of other listed types (not Enum, Collection, Map etc)

and you may need to implement both to see if type given should be handled by your deserializer.

@cowtowncoder
I debug jackson code in my project . GenderEnum will be go to factory.createEnumDeserializer(ctxt, type, beanDesc);,because
ClassUtil.isEnumType(type.getRawClass()) is always true for GenderEnum

    protected JsonDeserializer<?> _createDeserializer2(DeserializationContext ctxt,
            DeserializerFactory factory, JavaType type, BeanDescription beanDesc)
        throws JsonMappingException
    {
        final DeserializationConfig config = ctxt.getConfig();
        // If not, let's see which factory method to use
        // 12-Feb-20202, tatu: Need to ensure that not only all Enum implementations get
        //    there, but also `Enum` -- latter wrt [databind#2605], polymorphic usage
//        判断反序列化的类是否为枚举
        if (ClassUtil.isEnumType(type.getRawClass())) { // type.isEnumType()) {
            logger.info("\n====>反系列化的类是枚举[{}]");
            return factory.createEnumDeserializer(ctxt, type, beanDesc);
        }

then. if _findCustomEnumDeserializer(enumClass, config, beanDesc) return null, it will be deserialize by deser = new EnumDeserializer(constructEnumResolver(enumClass,config, beanDesc.findJsonValueAccessor()),config.isEnabled(MapperFeature.ACCEPT_CASE_INSENSITIVE_ENUMS));

      // 23-Nov-2010, tatu: Custom deserializer?
        JsonDeserializer<?> deser = _findCustomEnumDeserializer(enumClass, config, beanDesc);

last

         if (deser == null) {
                deser = new EnumDeserializer(constructEnumResolver(enumClass,
                        config, beanDesc.findJsonValueAccessor()),
                        config.isEnabled(MapperFeature.ACCEPT_CASE_INSENSITIVE_ENUMS));
                logger.info("\n====>为[{}]调用系统的默认枚举反序列化器[{}]",type,deser);
            }

if I want to get CustomEnumDeserializer , I have to make Enum.class to replace original,like this:

    deserializers.put(Enum.class, new BaseEnumDeserializer());
    jacksonObjectMapperBuilder.deserializersByType(deserializers);

I think it's so crazy, I am not sure what's going to happen. I just want to deserializer Enum implemented by BaseEnum.class implementation which defined by myself. I think I should only register BaseEnum.class to deserializers to deserialize Clazz (like GenderEnum.class)which implementes BaseEnum.class

SpringBoot how to register deserializers to jackson

com.fasterxml.jackson.databind.module.SimpleModule#addDeserializer

    /**
     * Method for adding deserializer to handle specified type.
     *<p>
     * WARNING! Type matching only uses type-erased {@code Class} and should NOT
     * be used when registering serializers for generic types like
     * {@link java.util.Collection} and {@link java.util.Map}.
     */
    public <T> SimpleModule addDeserializer(Class<T> type, JsonDeserializer<? extends T> deser)
    {
        logger.info("\n====>SpringBoot注入起点[{}]===>[{}]",type,deser);
        _checkNotNull(type, "type to register deserializer for");
        _checkNotNull(deser, "deserializer");
        if (_deserializers == null) {
            _deserializers = new SimpleDeserializers();
        }
        _deserializers.addDeserializer(type, deser);
        return this;
    }

com.fasterxml.jackson.databind.module.SimpleDeserializers#addDeserializer

    
    public <T> void addDeserializer(Class<T> forClass, JsonDeserializer<? extends T> deser)
    {
        ClassKey key = new ClassKey(forClass);
        if (_classMappings == null) {
            _classMappings = new HashMap<ClassKey,JsonDeserializer<?>>();
        }
//      =====>  全部添加到类里面了
        _classMappings.put(key, deser);
        // [Issue#227]: generic Enum deserializer?
        if (forClass == Enum.class) {
            _hasEnumDeserializer = true;
        }
    }

all class are registered to _classMappings

Last

1. I can register Enum.class to replace original EnumDeserializer , but that's not what I expected
2. it is simple to register deserializer to springboot
3. I support to add the below code to get Customer Enum Deserializer by super interface,like this

//            这里应该需要继续查找当前类的父接口，然后再是查找父类
            List<JavaType> interfaces = type.getInterfaces();
//            再次查找自定义的序列化器
            for (JavaType javaType : interfaces) {
                Class<?> rawClass = javaType.getRawClass();
                deser = _findCustomEnumDeserializer(rawClass, config, beanDesc);
                if (deser != null) {
                    logger.info("\n====>依据接口[{}]找到了反序列化器[{}]", rawClass, deser);
                    return deser;
                }
            }

@aohanhongzhi I think you are trying to dig too deep into internal handling here; regardless of whether type is Enum or not does not mean you could not register custom deserializer. But SimpleModule will probably not work since its Deserializers implementation (SimpleDeserializers) does not let you customize handling: you will need to be able to override method

findEnumDeserializer(...)

of Deserializers implementation registered: and in there you can use whatever logic you want -- for example one in this PR.
This logic should not be in the place PR suggests, however: I understand that it would solve your issue, but it is against the design unfortunately.

@cowtowncoder Thanks, I'll try to solve it with wrapper

public class SimpleDeserializersWrapper extends SimpleDeserializers {
    @Override
    public JsonDeserializer<?> findEnumDeserializer(Class<?> type, DeserializationConfig config, BeanDescription beanDesc) throws JsonMappingException {
        JsonDeserializer<?> enumDeserializer = super.findEnumDeserializer(type, config, beanDesc);
        if (enumDeserializer != null) {
            return enumDeserializer;
        }

        for (Class<?> typeInterface : type.getInterfaces()) {
            enumDeserializer = this._classMappings.get(new ClassKey(typeInterface));
            if (enumDeserializer != null) {
                return enumDeserializer;
            }
        }
        return null;
    }
}

// in spring java config

@Bean
public ObjectMapper objectMapper(Jackson2ObjectMapperBuilder builder) {
    SimpleDeserializersWrapper deserializers = new SimpleDeserializersWrapper();
    deserializers.addDeserializer(TypeEnum.class, new TypeEnumJsonDeserializer());

    SimpleModule simpleModule = new SimpleModule();
    simpleModule.setDeserializers(deserializers);
    simpleModule.addSerializer(TypeEnum.class, new TypeEnumJsonSerializer());

    ObjectMapper objectMapper = builder.createXmlMapper(false).build();
    objectMapper.registerModule(simpleModule);
    return objectMapper;
}

@ZGAOF Good work on overriding parts of SimpleDeserializers / SimpleModule -- I think this should do what you want?

@cowtowncoder @ZGAOF thank you very much for your help , which will help me solve the problem of customizing enumeration serialization. I've been working on it for a week and I've learned a lot from it. thank you !

@aohanhongzhi
If you want to set a unified custom serialization and deserialization for enums that implement an interface, you can also add the @jsonvalue annotation to the default method of the interface. No need to write custom Serializer and Deserializer.
如果想为实现interface的Enum设置统一的自定义序列化和反序列化，也可以在interface的default方法上添加@jsonvalue注解。不需要实现单独的Serializer and Deserializer。