可變引數需要慎用，不然scala 呼叫的時候會出現以下問題。

Error:(29, 31) ambiguous reference to overloaded definition,
both method toJSONString in object JSON of type (x$1: Any, x$2: com.alibaba.fastjson.serializer.SerializerFeature*)String
and  method toJSONString in object JSON of type (x$1: Any)String
match argument types
 
 (com.sydney.dream.example.fastjson.module.Group)
        val jsonString = JSON.toJSONString(group)

看原文程式碼, scala 不同於java 不知道呼叫哪一個函式，

public static String toJSONString(Object object) {
        return toJSONString(object, new SerializerFeature[0]);
    }

public static String toJSONString(Object object
 
, SerializerFeature... features) {
    SerializeWriter out = new SerializeWriter();

    try {
        JSONSerializer serializer = new JSONSerializer(out);
        for (com.alibaba.fastjson.serializer.SerializerFeature feature : features) {
            serializer.config(feature, true);
        }

        serializer.write(object
 
);

        return out.toString();
    } finally {
        out.close();
    }
}

所以我們呼叫的時候，顯式呼叫不定長引數的方法。
JSON.toJSONString(group, new ArraySerializeFilter)