使用Playframework 2.4 Json转换器实现Google PATCH语义 [英] Implementing Google PATCH semantic with Playframework 2.4 Json transformers

问题描述

我无法提出补丁语义的解决方案:

I can not come up with solution for Patch semantic:

1. 如果json没有属性，我需要跳过修改
2. 如果json属性具有null，则需要删除此属性(对于非必需属性)
3. 在其他情况下，我需要设置值

1. if json has no property, I need skip modification
2. if json property has null, I need to remove this property (for not required properties)
3. in other cases I need to set the value

我需要转换为mongo.db更新命令("$ unset"代表2，"$ set"代表3)

I need transformation into mongo.db update command ("$unset" for 2, "$set" for 3)

例如，我需要使用必填属性"summary" 存储json.所以:

For example I need store json with required property "summary". So:

{"summary": "modified by patch", "description": null}

必须转换为:

{
  "$set" : {
    "summary": "modified by patch"
  },
  "$unset": {
    "description": ""
  }
}

这个json

{"description": null}

必须转换为(跳过摘要"):

must be transformed to ("summary" is skipped):

{
  "$unset" : {
    "description": ""
  }
}

为此

{"summary": null}

我需要转换错误(无法删除必需的属性)

I need transformation error (can't remove required properties)

推荐答案

我的解决方案是

def patch(path: JsPath)(r: Reads[JsObject]) = Reads{json =>
  path.asSingleJsResult(json).fold(
    _ => JsSuccess(Json.obj()),
    _ => r.reads(json)
  )
}

以及所需的属性

def requiredError = ValidationError("error.remove.required")

val summaryPatch = patch(__ \ "summary")(
  (__ \ "$set" \ "summary").json.copyFrom( 
    (__ \ "summary").json.pick.filterNot(requiredError)(_ == JsNull)
  )
)

其他

val descriptionPatch = patch(__ \ "description")(
  (__ \ "$set" \ "description").json.copyFrom(
    (__ \ "description").json.pick.filterNot(_ == JsNull) 
  ) orElse 
  (__ \ "$unset" \ "description").json.copyFrom( 
    (__ \ "description").json.pick) 
  )
)

到mongo.db变形器:

toMongoPatch = (summaryPatch and descriptionPatch).reduce

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