Converting XML to JSON using XML Schema

Question

I would like to convert XML into JSON (concretely, a OAI-PMH response). I am currently using node.js xml2js, but the issue is that JSON is very verbose, with way to many levels of nesting and arrays, even when there is only one element as a child and will never be more than one. The issue is that xml2js does not know anything about the schema of the XML file, so it has to be conservative.

My question is, is there any other (preferably JavaScript) code which would use XML Schema to guide conversion process? So if schema defines types and structure of XML, that than JSON takes advantage of this and have correct types automatically, and not unnecessary array levels.

Answer 1

I had a similar, but opposite, problem with X2JS : it would not create a list if there was only one child element ( even when it should be a list ). The solution ( for me ) was to supply the extra options "arrayFormPaths" to the converter -- this causes matching elements to become an array, even if there is only one element.

I agree that there should be a way to do this using an XML Schema...but I couldn't find anything either.

Answer 2

At the end, I decided just to implement such a package: xml4js.

So for XML taken from XML Primer:

<?xml version="1.0"?>
<purchaseOrder orderDate="1999-10-20" xmlns="http://www.example.com/PO">
   <shipTo country="US">
      <name>Alice Smith</name>
      <street>123 Maple Street</street>
      <city>Mill Valley</city>
      <state>CA</state>
      <zip>90952</zip>
   </shipTo>
   <billTo country="US">
      <name>Robert Smith</name>
      <street>8 Oak Avenue</street>
      <city>Old Town</city>
      <state>PA</state>
      <zip>95819</zip>
   </billTo>
   <comment>Hurry, my lawn is going wild!</comment>
   <items>
      <item partNum="872-AA">
         <productName>Lawnmower</productName>
         <quantity>1</quantity>
         <USPrice>148.95</USPrice>
         <comment>Confirm this is electric</comment>
      </item>
      <item partNum="926-AA">
         <productName>Baby Monitor</productName>
         <quantity>1</quantity>
         <USPrice>39.98</USPrice>
         <shipDate>1999-05-21</shipDate>
      </item>
   </items>
</purchaseOrder>

Without using a XML Schema to guide a conversion process, with explicit arrays turned on, you would get:

{
  "purchaseOrder": {
    "$": {
      "orderDate": "1999-10-20",
      "xmlns": "http://www.example.com/PO"
    },
    "shipTo": [
      {
        "$": {
          "country": "US"
        },
        "name": [
          "Alice Smith"
        ],
        "street": [
          "123 Maple Street"
        ],
        "city": [
          "Mill Valley"
        ],
        "state": [
          "CA"
        ],
        "zip": [
          "90952"
        ]
      }
    ],
    "billTo": [
      {
        "$": {
          "country": "US"
        },
        "name": [
          "Robert Smith"
        ],
        "street": [
          "8 Oak Avenue"
        ],
        "city": [
          "Old Town"
        ],
        "state": [
          "PA"
        ],
        "zip": [
          "95819"
        ]
      }
    ],
    "comment": [
      "Hurry, my lawn is going wild!"
    ],
    "items": [
      {
        "item": [
          {
            "$": {
              "partNum": "872-AA"
            },
            "productName": [
              "Lawnmower"
            ],
            "quantity": [
              "1"
            ],
            "USPrice": [
              "148.95"
            ],
            "comment": [
              "Confirm this is electric"
            ]
          },
          {
            "$": {
              "partNum": "926-AA"
            },
            "productName": [
              "Baby Monitor"
            ],
            "quantity": [
              "1"
            ],
            "USPrice": [
              "39.98"
            ],
            "shipDate": [
              "1999-05-21"
            ]
          }
        ]
      }
    ]
  }
}

But the package gives you this:

{
  "purchaseOrder": {
    "$": {
      "orderDate": "1999-10-20T00:00:00.000Z"
    },
    "shipTo": {
      "$": {
        "country": "US"
      },
      "name": "Alice Smith",
      "street": "123 Maple Street",
      "city": "Mill Valley",
      "state": "CA",
      "zip": 90952
    },
    "billTo": {
      "$": {
        "country": "US"
      },
      "name": "Robert Smith",
      "street": "8 Oak Avenue",
      "city": "Old Town",
      "state": "PA",
      "zip": 95819
    },
    "comment": "Hurry, my lawn is going wild!",
    "items": {
      "item": [
        {
          "$": {
            "partNum": "872-AA"
          },
          "productName": "Lawnmower",
          "quantity": 1,
          "USPrice": 148.95,
          "comment": "Confirm this is electric"
        },
        {
          "$": {
            "partNum": "926-AA"
          },
          "productName": "Baby Monitor",
          "quantity": 1,
          "USPrice": 39.98,
          "shipDate": "1999-05-21T00:00:00.000Z"
        }
      ]
    }
  }
}