select mongodb aray element in a single field in pentaho PDI

问题

Following is the structure of the document i have in a collection in MongoDB

{
    "_id": {
        "$oid": "5f48e358d43721376c397f53"
    },
    "heading": "this is heading",
    "tags": ["tag1","tag2","tag3"],
    "categories": ["projA", "projectA2"],
    "content": ["This", "is", "the", "content", "of", "the", "document"],
    "timestamp": 1598612312.506219,
    "lang": "en"
}

When i am importing data in PDI using the mongodb input step the system is putting each array of the "content" element in a different field I want to select each element in one field (concat the array type elements). for example in the attached image above i want one content field with all the arrays concatenated How do i do that?

来源：https://stackoverflow.com/questions/64764408/select-mongodb-aray-element-in-a-single-field-in-pentaho-pdi