Scala Gson，无法序列化Option [Blob]

我设法扩展了Gson以处理Scala的 Option 和 Blob 类型，但是我对合并的 Option [java.sql.Blob] 遇到麻烦代码>.

I managed to extend Gson to handle Scala's Option and Blob types, but I have trouble with the combined Option[java.sql.Blob].

我的测试说

[info]-应该序列化一个选项-确定

[info] - should serialize an Option - OK

[info]-应该序列化Blob-确定

[info] - should serialize a Blob - OK

[info]-应该序列化Option [Blob] *失败*

[info] - should serialize an Option[Blob] * FAILED *

[info] {"x":{"buf":[97,115,100,102]，"len":4，"origLen":4}}不等于{"x":"asdf"}

[info] {"x":{"buf":[97,115,100,102],"len":4,"origLen":4}} was not equal to {"x":"asdf"}

能否请您告诉我这个 {"buf":[...]} 对象是什么，以及为什么Gson会这样做?我的序列化程序(如下))绝对告诉他用它创建一个String，但该对象甚至没有被引用.

Can you please tell me what this {"buf": [...]} object is, and possibly why Gson is doing that? My serializer (below) definitely tells him to make a String from it, yet this object is even unquoted.

FWIW，尝试用真实的Blob序列化具有Option [Blob]字段的真实对象(数据库行)，我什至会收到*错误.

FWIW, trying to serialize real-life objects (database rows) that have Option[Blob] fields with real Blobs, I even get a * error.

这是我写序列化器的方式:

Here is how I wrote the serializers:

class OptionSerializer extends JsonSerializer[Option[Any]] {
  def serialize(src: Option[Any], typeOfSrc: Type, context: JsonSerializationContext): JsonElement = {
    src match {
      case None => JsonNull.INSTANCE
      case Some(v) => context.serialize(v)
    }
  }
}

class BlobSerializer extends JsonSerializer[java.sql.Blob] {
  override def serialize(src: java.sql.Blob, typeOfSrc: Type, context: JsonSerializationContext): JsonElement = {
    val s: String = utils.blob2String(v)
    context.serialize(s)
  }
}

class BlobOptionSerializer extends JsonSerializer[Option[java.sql.Blob]] {
  override def serialize(src: Option[java.sql.Blob], typeOfSrc: Type, context: JsonSerializationContext): JsonElement = {
    src match {
      case None => JsonNull.INSTANCE
      case Some(v: java.sql.Blob) =>
        val s: String = utils.blob2String(v)
        context.serialize(s)
    }
  }
}

private val builder = new GsonBuilder()
builder.registerTypeAdapter(classOf[java.sql.Blob], new BlobSerializer)
builder.registerTypeAdapter(classOf[Option[java.sql.Blob]], new BlobOptionSerializer)
builder.registerTypeAdapter(classOf[Option[Any]], new OptionSerializer)
val gson = builder.create()

产生以上结果的测试:

case class B(x: Option[Int], y: String)
case class C(x: java.sql.Blob)
case class D(x: Option[java.sql.Blob])

"serialize options" in {
  val b = B(Some(1), "asdf")
  gson.toJson(b) must be ("{\"x\":1,\"y\":\"asdf\"}")
}

"serialize a Blob" in {
  val c = C(utils.string2Blob("asdf"))
  gson.toJson(c) must be ("{\"x\":\"asdf\"}")
}

"serialize an Option[Blob]" in {
  val d = D(Some(utils.string2Blob("asdf")))
  gson.toJson(d) must be ("{\"x\":\"asdf\"}")
}

还有我从Blob到Blob的转换方法，以防万一:

And my conversion methods from and to Blob, just in case:

def string2Blob(s: String) = {
  new SerialBlob(s.getBytes)
}

def blob2String(blob: java.sql.Blob): String = {
  if (blob.length == 0)
    return ""  // Array[Byte]()
  val b: Array[Byte] = blob.getBytes(1, blob.length.toInt)
  blob.free
  new String(b)
}