java - 如何使用 Jackson 反序列化枚举？

Question

用户发帖 {"lang": ["en_US", "en_UK"]}到 REST API。我想填充一个具有此属性的对象 List<EnmLanguage> lang; .除了 JSON 数组外，其他所有东西都有效。

我的 EnmLanguage.java 是:

@JsonSerialize(
    using = BaseEnumSerializer.class
)
@JsonDeserialize(
    using = BaseEnumDeserializer.class
)
public enum EnmLanguage implements BaseEnum, Serializable {
    en_US {
        public String getCode() {
            return "en_US";
        }

        public String getText(EnmLanguage s) {
            return s == EnmLanguage.en_US ? "English" : "İngilizce";
        }
    },

我的 BaseEnum.java 是:

public interface BaseEnum {
    Object getCode();

    String getText(EnmLanguage lang);

    default String getText() {
        return this.getText(EnmLanguage.tr_TR);
    }

    default Map<String, Object> getMap(EnmLanguage lang) {
        return new HashMap<String, Object>() {
            {
                this.put("name", BaseEnum.this.getText(lang));
                this.put("id", BaseEnum.this.getCode());
            }
        };
    }

    default Map<String, Object> getMap() {
        return this.getMap(EnmLanguage.tr_TR);
    }

    static <T extends Enum<T> & BaseEnum> T fromCode(Class<T> parent, Object code) {
        Map<Object, T> lookup = new HashMap();
        Enum[] var3 = (Enum[])parent.getEnumConstants();
        int var4 = var3.length;

        for(int var5 = 0; var5 < var4; ++var5) {
            T d = var3[var5];
            lookup.put(((BaseEnum)d).getCode().toString(), d);
        }

        return (Enum)lookup.get(code.toString());
    }
}

我的 BaseEnumDeserialiazer 是:

public class BaseEnumDeserializer<T extends Enum<T> & BaseEnum> extends StdDeserializer<T> {
    public BaseEnumDeserializer() {
        this((Class)null);
    }

    public BaseEnumDeserializer(Class<T> vc) {
        super(vc);
    }

    public T deserialize(JsonParser jsonparser, DeserializationContext context) throws IOException {
        Field field = this.findField(jsonparser.getCurrentName(), jsonparser.getCurrentValue().getClass());
        Class<T> javaType = field.getType();
        return BaseEnum.fromCode(javaType, jsonparser.getText());
    }

    public Field findField(String name, Class<?> c) {
        while(c != null) {
            Field[] var3 = c.getDeclaredFields();
            int var4 = var3.length;

            for(int var5 = 0; var5 < var4; ++var5) {
                Field field = var3[var5];
                if (!Modifier.isStatic(field.getModifiers()) && field.getName().equals(name)) {
                    return field;
                }
            }

            c = c.getSuperclass();
        }

        return null;
    }
}

但最后它没有转换 "lang": ["en_US", "en_UK"]进入List的 EnmLanguage .我认为它不知道到哪个 BaseEnum兑换。我应该如何让它知道它应该将其转换为 List<EnmLanguage> ？

Answer 1

对于您的特定情况，在基本类型中添加静态 @JsonCreator 方法可能就足够了。

interface Lang {
    @JsonCreator
    static Lang valueOf(String value) {
        return Languages.valueOf(value);
    }
}

@JsonFormat(shape = JsonFormat.Shape.STRING)
enum Languages implements Lang {
    en_US,
    en_GB
}

然后你可以像解析其他类一样解析它

class LangTest {
    private final ObjectMapper mapper = new ObjectMapper()
            .setAnnotationIntrospector(new JacksonAnnotationIntrospector());

    @Test
    void readsJson() throws IOException {
        final Lang[] tree = this.mapper
                .readerFor(Lang[].class)
                .readValue("[\"en_US\", \"en_GB\"]");
        Assertions.assertArrayEquals(
                tree,
                new Lang[]{
                        Languages.en_US,
                        Languages.en_GB
                }
        );
    }
}