scala调用fastjson JSON.toJSONString()序列化对象出错

在scala中需要将case class 序列化为string，代码如下

results.map(JSON.toJSONString(_)).foreach(println)

case class pay(id:String)

然后出现下面的错误

Error:(35, 12) 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 (PayTest.this.pay)
      JSON.toJSONString(t)

查看FastJson toJSONString发现有个可变参数相同的方法,结合错误应该是scala不知道调用哪个方法导致的

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

    public static final 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();
        }
    }

我们直接在代码指定调用可变参数的方法，SerializerFeature是个枚举，我们直接选择第一个

results.map(JSON.toJSONString(_, SerializerFeature.QuoteFieldNames)).foreach(println)

但是出现的结果不是想要的,class的字段都没有序列化出来

{}

其实fastjson 默认是基于方法clz.getMethods()进行字段查找过滤的,而scala中的getter和setter方法完全不是java那种命名方式。scala中的getter:def foo():T setter: def foo_(val:T):Unit因此如果采用默认配置序列化scala对象，会出现如上问题。但是我们可以加上BeanProperty，目的是让这个类有getter和setter方法

case class pay(@BeanProperty id:String)

最后结果为

{"id":"1"}

另外我们还有一种基于Jackson的方式

  def objectParse = new RichMapFunction[pay, String] {
    private var mapper: ObjectMapper = _

    override def open(parameters: Configuration): Unit = {
      this.mapper = new ObjectMapper()
    }

    override def map(value: pay): String = {
      mapper.writeValueAsString(value)
    }
  }

results.map(objectParse).foreach(println)

参考：https://github.com/alibaba/fastjson/issues/1282