Migrate JsonDeserializer from Java to Kotlin

Remove all null elements

filterNotNull 方法会把一个 nullable list 转成一个 non-null list，所以articleList 必须定义为nullable List，否则IDE提示 useless call on collection type:

class ArticlesDeserializer @Inject constructor() : JsonDeserializer<List<Article>> {
    @Throws(JsonParseException::class)
    override fun deserialize(json: JsonElement, typeOfT: Type, context: JsonDeserializationContext): List<Article> {
        val jsonObject = json.asJsonObject
        val type = object : TypeToken<ArrayList<Article>>() {}.type
        val articleList = context.deserialize<List<Article?>>(jsonObject.get("rows"), type)
        return articleList.filterNotNull()
    }
}

Java codes:

// remove all null elements
articleList.removeAll(Collections.singleton(null));

通过注解抛出异常

@Throws(JsonParseException::class)
override fun deserialize(json: JsonElement, typeOfT: Type, context: JsonDeserializationContext): List<Article> {
}

Java codes:

@Override
public List<Article> deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
    throws JsonParseException {
}

2018-08-27 Weiyi Li