自定义枚举 --- Gson转换

通过Restful接口返回的JSON数据默认是枚举的名字，但是使用自定义枚举时，一般统一使用自定义的code来代表。所以需要自定义HttpMessageConverter

CodedTypeTypeAdapter

import com.google.gson.*;
import com.utils.mybatis.CodedEnum;

import java.lang.reflect.Type;

/**
 * CodedEnum在GSON中的转换规则，使用code，而不是字符
 *
 * @param <E>
 * @author tenmao
 */
public class CodedTypeTypeAdapter<E extends Enum<E> & CodedEnum> implements JsonSerializer<E>, JsonDeserializer<E> {
    @Override
    public E deserialize(JsonElement jsonElement, Type type, JsonDeserializationContext jsonDeserializationContext) throws JsonParseException {
        if (type instanceof Class) {
            @SuppressWarnings("unchecked")
            Class<E> klass = (Class<E>) type;
            return CodedEnum.codeOf(klass, jsonElement.getAsInt()).orElse(null);
        } else {
            throw new RuntimeException(String.format("json %s cannot convert to type %s", jsonElement, type));
        }
    }

    @Override
    public JsonElement serialize(E e, Type type, JsonSerializationContext jsonSerializationContext) {
        return new JsonPrimitive(e.getCode());
    }
}

HttpMessageConverter

import com.google.gson.GsonBuilder;
import com.tenmao.utils.mybatis.CodedEnum;
import com.tenmao.utils.mybatis.converter.CodedTypeTypeAdapter;
import lombok.extern.slf4j.Slf4j;
import org.reflections.Reflections;
import org.reflections.scanners.SubTypesScanner;
import org.springframework.http.converter.json.GsonHttpMessageConverter;

import java.util.Set;

/**
 * @author tenmao
 * @since 2017/12/1
 */
@Slf4j
public class HttpMessageConverter extends GsonHttpMessageConverter {
    public HttpMessageConverter() {
        final GsonBuilder builder = new GsonBuilder();
        final Reflections reflections = new Reflections("com.tenmao", new SubTypesScanner(true));
        final Set<String> allClasses = reflections.getStore().getSubTypesOf(CodedEnum.class.getName());
        for (String klass : allClasses) {
            try {
                final Class<?> aClass = Class.forName(klass);
                builder.registerTypeAdapter(aClass, new CodedTypeTypeAdapter<>());
            } catch (ClassNotFoundException e) {
                log.error("fail to register for gson", e);
            }
        }
        setGson(builder.create());
    }
}

spring-mvc.xml

<mvc:annotation-driven>
      <mvc:message-converters>
            <bean class="com.tenmao.web.mvc.support.HttpMessageConverter" />
      </mvc:message-converters>
</mvc:annotation-driven>

完成

实现上述步骤后，只要实现接口CodedEnum的自定义枚举都可以自动转换为其code值

自定义枚举系列

• 自定义枚举 --- MyBatis字段映射
• 自定义枚举 --- Swagger文档展示