如何将 Scala Map 转换为 JSON 字符串? [英] How to convert Scala Map into JSON String?

问题描述

例如，我在 Scala 中有这个 Map 值:

For example, I have this Map value in Scala:

val m = Map(
    "name" -> "john doe", 
    "age" -> 18, 
    "hasChild" -> true, 
    "childs" -> List(
        Map("name" -> "dorothy", "age" -> 5, "hasChild" -> false),
        Map("name" -> "bill", "age" -> 8, "hasChild" -> false)
    )
)

我想把它转换成它的 JSON 字符串表示:

I want to convert it to its JSON string representation:

{
    "name": "john doe",
    "age": 18,
    "hasChild": true,
    "childs": [
        {
            "name": "dorothy",
            "age": 5,
            "hasChild": false
        },
        {
            "name": "bill",
            "age": 8,
            "hasChild": false
        }
    ]
}

我目前正在研究 Play 框架 v2.3，但该解决方案不需要使用 Play JSON 库，尽管如果有人可以提供 Play 和非 Play 解决方案会很好.

I'm currenly working on Play framework v2.3, but the solution doesn't need to use Play JSON library, although it will be nice if someone can provide both Play and non-Play solution.

这是我迄今为止所做的没有成功的事情:

This is what I have done so far without success:

// using jackson library
val mapper = new ObjectMapper()
val res = mapper.writeValueAsString(m)
println(res)

结果:

{"empty":false,"traversableAgain":true}

我不明白为什么会得到这样的结果.

I don't understand why I got that result.

推荐答案

作为非 play 解决方案，可以考虑使用 json4s它为 jackson 提供了一个包装器，并且易于使用.如果您使用的是 json4s，那么您只需使用以下命令即可将地图转换为 json:

As a non play solution, you can consider using json4s which provides a wrapper around jackson and its easy to use. If you are using json4s then you can convert map to json just by using:

write(m)                                        
//> res0: String = {"name":"john doe","age":18,"hasChild":true,"childs":[{"name":"dorothy","age":5,"hasChild":false},{"name":"bill","age":8,"hasChild":false}]}

--更新以包含完整示例--

--Updating to include the full example--

import org.json4s._
import org.json4s.native.Serialization._
import org.json4s.native.Serialization
implicit val formats = Serialization.formats(NoTypeHints)

 val m = Map(
  "name" -> "john doe",
  "age" -> 18,
  "hasChild" -> true,
  "childs" -> List(
    Map("name" -> "dorothy", "age" -> 5, "hasChild" -> false),
    Map("name" -> "bill", "age" -> 8, "hasChild" -> false)))

 write(m)

输出:

 res0: String = {"name":"john doe","age":18,"hasChild":true,"childs":[{"name" 
 :"dorothy","age":5,"hasChild":false},{"name":"bill","age":8,"hasChild":false }]}

替代方式:

import org.json4s.native.Json
import org.json4s.DefaultFormats

Json(DefaultFormats).write(m)

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