Scala - 将 Json 对象写入文件并读取它
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Scala - Writing Json object to file and reading it
提问by yAsH
I have a Map like below
我有一张像下面这样的地图
val map : scala.collection.mutable.Map[String,Any] = Map(
dummy1 -> ["cat1", "hash1", 101, 1373269076, {"1" : ["dummy", "dummy", "dummy"]}],
dummy2 -> ["cat1", "hash1", 102, 1373269076, {"2" : ["dummy", "dummy", "dummy"]}],
dummy3 -> ["cat1", "hash1", 103, 1373269076, {"3" : ["dummy", "dummy", "dummy"]}]
)
I converted it into a Json string and then wrote it into a file with the code below
我将其转换为 Json 字符串，然后使用以下代码将其写入文件
Some(new PrintWriter("foo.txt")).foreach{p =>
p.write(JSONObject(map.toMap).toString()); p.close
}
Am able to read the Json string from the file using
能够使用从文件中读取 Json 字符串
val json_string = scala.io.Source.fromFile("foo.txt").getLines.mkString
How do I get my map back from the Json string above?
如何从上面的 Json 字符串中取回我的地图？
EDIT:Am able to read the map with
编辑：我能够阅读地图
val map1 = JSON.parseFull(json_string).get.asInstanceOf[Map[String,Any]]
But, this process is taking more time as the size of the map increases.
但是，随着地图大小的增加，这个过程需要更多的时间。
采纳答案by Bruno Grieder
Try using a likely faster (and more thorough) mapper.
尝试使用可能更快（更彻底）的映射器。
I would recommend using HymansMapperwhich wraps the excellent Hymansonfor a more pleasant Scala usage.
我会推荐使用HymansMapper，它包装了优秀的Hymanson以获得更愉快的 Scala 使用。
Serializing to JSON becomes as simple as
序列化为 JSON 变得如此简单
val json = HymansMapper.writeValueAsString[MyClass](instance)
... and deserializing
...和反序列化
val obj = HymansMapper.readValue[MyClass](json)
(edit)
（编辑）
You can make also writing and reading simple one-liners using FileUtils from commons-iodoing
您可以同时写入和读取使用简单的单行文件实用程序从公共-IO做
val json = FileUtils readFileToString (file, encoding)
and
和
FileUtils write (file, json, encoding)
回答by Greg
I actually got a lot more use from json4s. The documentation is much more clear and comprehensive, and the usage seems slightly easier.
我实际上从json4s得到了更多的使用。文档更加清晰和全面，使用起来似乎稍微容易一些。
A similar operation to the one you are requesting would look like this
与您请求的操作类似的操作如下所示
import org.json4s.native.JsonFormats.parse
... get your json string ...
val parsedJson = parse(json)
val extractedJson = parsedJson.extract[MyClass]
