我有以下针对json4s的Scala控制台 session ,在这里我试图从已解析的json中提取String值:
scala> import org.json4s._
import org.json4s._
scala> import org.json4s.native.JsonMethods._
import org.json4s.native.JsonMethods._
scala> val s = """ {"a": "hello"} """
s: String = " {"a": "hello"} "
scala> val json = parse(s)
json: org.json4s.JValue = JObject(List((a,JString(hello))))
scala> json \ "a"
res0: org.json4s.JValue = JString(hello)
scala> res0.extract[String]
<console>:17: error: No org.json4s.Formats found. Try to bring an instance of org.json4s.Formats in scope or use the org.json4s.DefaultFormats.
res0.extract[String]
^
scala> import org.json4s.Formats._
import org.json4s.Formats._
scala> res0.extract[String]
<console>:20: error: No org.json4s.Formats found. Try to bring an instance of org.json4s.Formats in scope or use the org.json4s.DefaultFormats.
res0.extract[String]
^
scala> import org.json4s.DefaultFormats._
import org.json4s.DefaultFormats._
scala> res0.extract[String]
<console>:23: error: No org.json4s.Formats found. Try to bring an instance of org.json4s.Formats in scope or use the org.json4s.DefaultFormats.
res0.extract[String]
^
org.json4s.DefaultFormats
,org.json4s.Formats
及其成员已经在范围内。我怎样才能解决这个问题?EDIT1
从
@mfirry
的答案,这可以工作:scala> implicit val formats = DefaultFormats
formats: org.json4s.DefaultFormats.type = org.json4s.DefaultFormats$@12b195f5
scala> val json = parse(""" {"a": "hello", "b": 1.2} """)
json: org.json4s.JValue = JObject(List((a,JString(hello)), (b,JDouble(1.2))))
scala> (json \ "b").extract[String]
res6: String = 1.2
scala> (json \ "b").extract[Double]
res7: Double = 1.2
最佳答案
您只需要添加
implicit val formats = DefaultFormats
一切都会好的。
关于scala - 使用json4s提取字符串值,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/32378429/