如何使用data Factory遍历文件夹并合并其中的所有文件？

{
  "name": "MergeFilesPipeline",
  "properties": {
    "activities": [
      {
        "name": "GetMetadata",
        "type": "GetMetadata",
        "typeProperties": {
          "dataset": {
            "referenceName": "SourceFolderDataset",
            "type": "DatasetReference"
          },
          "fieldList": [
            "childItems"
          ]
        }
      },
      {
        "name": "ForEachFile",
        "type": "ForEach",
        "typeProperties": {
          "items": {
            "type": "Expression",
            "value": "@activity('GetMetadata').output.childItems"
          },
          "activities": [
            {
              "name": "CopyFile",
              "type": "Copy",
              "typeProperties": {
                "source": {
                  "type": "FileSystemSource",
                  "recursive": "false"
                },
                "sink": {
                  "type": "FileSystemSink"
                },
                "translator": {
                  "type": "TabularTranslator",
                  "mappings": [
                    {
                      "source": {
                        "path": "."
                      },
                      "sink": {
                        "path": "merged/$(item().name)"
                      }
                    }
                  ]
                }
              },
              "inputs": [
                {
                  "referenceName": "SourceFileDataset",
                  "type": "DatasetReference",
                  "parameters": {
                    "fileName": {
                      "value": "@item().name"
                    }
                  }
                }
              ],
              "outputs": [
                {
                  "referenceName": "TargetFolderDataset",
                  "type": "DatasetReference"
                }
              ]
            }
          ]
        }
      }
    ]
  }
}