在 Datasnap 中旋转数据集 JSON 结果 (Delphi 10)

Question

我正在尝试旋转 Datasnap 返回的数据集的结果。

示例：这是我得到的

{"result":[{"table":[["REG_KEY",1,0,0,2,3,0,0,false,false,0,false,false],["REG_NAME",1,1,0,128,129,0,0,false,false,0,false,false]],"REG_KEY":["01","02"],"REG_NAME":["BALEARES","CANARIAS"]}]}

我想将其转换为：

[{"REG_KEY":"01","REG_NAME":"BALEARES"},{"REG_KEY":"02","REG_NAME":"CANARIAS"}]

我打算在 DSHTTPWebDispatcher.FormatResult 内转换它，但这是我第一次使用 DataSnap/REST/JSON，我在理解类来管理 JSON 值时遇到问题。

应该是这样的：

procedure TWebModule1.DSHTTPWebDispatcher1FormatResult(Sender: TObject; var ResultVal: TJSONValue; const Command: TDBXCommand; var Handled: Boolean);
var
    Aux: TJSONObject;
    NewResult: TJSONObject;
    Row: TJSONObject;
    NumField, NumRow, MaxFields, MaxRows: integer;
begin
    Handled := True;
    NewResult := TJSONArray.Create;
    Aux := TJSONArray(ResultVal).Get(0);  // I get the result as an Object instead of an Array
    MaxFields := Aux.Pairs.Count - 1; // I ignore the Pair 0 because it only contains the Dataset structure
    MaxRows := TJSONArray(1).Count;
    for NumRow := 0 to MaxRows - 1 do begin
        Row := TJSONObject.Create;
        for NumField := 1 to MaxFields do begin
            Row.AddPair(Aux.Pairs[NumField].JsonString, 
                        TJSONArray(Aux.Pairs[NumField].JsonValue).Get(NumRow));
        end;
        Aux.Add(Row);
    end;
    Aux.Free;
    ResultVal.Free;
    ResultVal := NewResult;
end;

但是TJSONObject没有Pairs.Count方法知道包含多少对，TJSONArray也没有直接Add方法添加一个新对象。我很确定这段代码还有很多其他错误。

有人可以指导我如何解决吗？

Answer 1

我明白了:-)

此代码执行我寻找的转换（它执行双循环遍历行和列，并在新的 JSON 中旋转结果）：

procedure TWebModule1.DSHTTPWebDispatcher1FormatResult(Sender: TObject; var ResultVal: TJSONValue; const Command: TDBXCommand; var Handled: Boolean);
var Aux: TJSONObject;
    NewResult: TJSONValue;
    Row: TJSONObject;
    NumField, NumRow, MaxFields, MaxRows: integer;
begin  
  Handled := True;

  if ResultVal.ToJSON = '[{"table":[]}]' then begin
    TJSONArray(ResultVal).Remove(0);
  end
  else if (LowerCase(Copy(ResultVal.ToJSON, 1, 10)) = '[{"table":') then begin // For Datasets I rotate its content so it comes as rows and not as columns
    NewResult := TJSONArray.Create;
    Aux := TJSONObject(TJSONArray(ResultVal).Get(0));

    MaxFields := Aux.Count - 1;  // I ignore the Pair 0 because it only contains the Dataset structure
    MaxRows := TJSONArray(TJSONPair(Aux.Get(1)).JSONValue).Count;

    for NumRows := 0 to MaxRows - 1 do begin
      Row := TJSONObject.Create;
      for NumFields := 1 to MaxFields do begin
        Row.AddPair(Aux.Pairs[NumField].JsonString.Value,
                     TJSONArray(Aux.Pairs[NumField].JsonValue).Get(NumRow).Clone as TJSONValue);
      end;
      TJSONArray(NewResult).AddElement(Row);
    end;

    ResultVal.Free;              // I free the old Result because a new one is returned (Aux is already supposed to be freed when freeing ResultVal)
    ResultVal := NewResult;       
  end;
end;

Answer 2

将其放入 Web 模块

procedure TWebModule1.DSHTTPWebDispatcher1FormatResult(Sender: TObject;
 var ResultVal: TJSONValue; const Command: TDBXCommand;
              var Handled: Boolean);
var
  Aux: TJSONValue;
begin
    Aux := ResultVal;
    ResultVal := TJSONArray(Aux).Get(0);
    TJSONArray(Aux).Remove(0);
    Aux.Free;
end;

你的结果会是这样

{"result":[{...},{...}]}

在 Datasnap 中旋转数据集 JSON 结果 (Delphi 10)

Rotate a Dataset JSON Result in Datasnap (Delphi 10)

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