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.

Mitar · Accepted Answer · 2014-06-20 05:44:48Z

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"
        }
      ]
    }
  }
}

The example which is attached are not working as expected.github.com/peerlibrary/node-xml4js Any help, would be greatly helpful

Nick Perkins · Accepted Answer · 2014-06-13 20:06:20Z

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.

answered Jun 13, 2014 at 20:06

Nick Perkins

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2 Comments

JohnK Over a year ago

@Mitar, that looks promising. Any plans to update it? I just tried installing: "found 13 vulnerabilities (1 low, 10 moderate, 2 high)"

Marcel Over a year ago

Where can I find your referenced X2JS library? It seems distinct from the OP's xml2js, as I can not find your "arrayFormPaths" option there. Is it this one here? github.com/abdolence/x2js

goodman · Accepted Answer · 2018-04-20 13:01:13Z

0

Found the following project library on GitHub that does the job : Schema Aware XML to JSON translator .

This library does the job in java. It is still not fully mature but does the conversion using the Schema provided.

answered Apr 20, 2018 at 13:01

goodman

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Comments

Wildhammer · Accepted Answer · 2022-08-26 14:17:45Z

0

There is a very well maintained python package named xmlschema that would do that without any hassle.

Using to_dict method.

import xmlschema
import simplejson as json

my_schema = xmlschema.XMLSchema("../shiporder.xsd")
obj = my_schema.to_dict('../shiporder.xml')
# in case you want to save the json in a file
json.dumps(obj)

You can get the example xml and xsd for ship order from w3schools. Once downloaded try to leave only one item in the ship order xml and see how the schema retains the array type. The number types are also preserved after conversion to json.

answered Aug 26, 2022 at 14:17

Wildhammer

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1 Comment

user358041 Over a year ago

I tried this approach. It seems xmlschema or simplejson have a dependency on Counter which is only available in Python 2.7. However xmlschema won't install on Python 2.7.

jschnasse · Accepted Answer · 2018-12-17 07:13:22Z

-1

If you are looking for a java solution.

A solution using standard jdk tool xjc can be found here:
Convert xml to json with Java . With xjc one can create Java classes from an XML Schema and use JAXB tools to read in an write out data in different formats.
If you want to convert directly from XML file, you can use this library from Json.org like described here:
Quickest way to convert XML to JSON in Java

edited Dec 17, 2018 at 7:13

answered Apr 23, 2018 at 9:32

jschnasse

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Comments

ceving · Accepted Answer · 2014-06-14 17:30:25Z

-5

An XML schema is used for XML validation. It is not possible to convert anything with a XML schema. A schema defines the structure of an XML document. If you want to convert something you need a XSLT which is a XML transformation specification. See here how to do it in JavaScript: http://www.w3schools.com/xsl/xsl_client.asp

edited Jun 14, 2014 at 17:30

answered Jun 13, 2014 at 9:37

ceving

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5 Comments

Mitar Over a year ago

I want to convert structure of XML document into JSON. And of course it can help. For example, maxOccurs can help you know if you should create an array or not (if maxOccurs is 1, you do not need an array). And type can help you convert to JSON types.

ceving Over a year ago

@Mitar You can convert a XML schema to JSON, but this also requires XSLT. A schema does not convert anything.

Mitar Over a year ago

I am saying that schema could be used to help in the conversion process.

ceving Over a year ago

@Mitar Yes a text editor could also help the transformation process.

gvlx Over a year ago

npmjs.com/package/xml4js "Package builds upon node-xml2js, detects and parses XML Schema which is then used to transform JavaScript object into a consistent schema-driven structure."

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