XML to terse JSON

This is a project to convert XML documents to JSON. It does this by taking a disciplined approach to create a terse JSON structure. The library has support for node types such as comments and processing instructions.

DTDs are experimentally supported (a node will be created for them), but entity references are unpacked, i.e., < in XML becomes < in JSON.

Motivation

There are a bunch of libraries out there that convert, most notably in org.json.XML. The problem with most XML-to-JSON implementations is that we lose a lot of information about ordering / attributes / whatever.

Another motivation was to have a more light-weight JSON serialization of XML, since lossless transformations tend to be wordy. In this library, we trade off some readability for a reduction in bytes. JSON output for this library is typically only slightly larger in bytesize than the XML input.

Usage

Download the latest JAR or grab from Maven:

<dependencies>
        <dependency>
            <groupId>org.leibnizcenter</groupId>
            <artifactId>xml-to-json</artifactId>
            <version>0.9.2</version>
        </dependency>
</dependencies>

or Gradle:

compile 'org.leibnizcenter:xml-to-json:0.9.2'

import com.google.gson.Gson;
import org.leibnizcenter.xml.helpers.DomHelper;
import org.leibnizcenter.xml.NotImplemented;
import org.leibnizcenter.xml.TerseJson;
import org.w3c.dom.Document;
import org.xml.sax.SAXException;

import javax.xml.parsers.ParserConfigurationException;
import java.io.IOException;

public class Main {
    private static final TerseJson.WhitespaceBehaviour COMPACT_WHITE_SPACE = TerseJson.WhitespaceBehaviour.Compact;

    public static void main(String[] args) throws IOException, SAXException, ParserConfigurationException, NotImplemented {
        String xml = ("<root>" +
                "<!-- thïs ïs à cómmënt. -->" +
                "  <el ampersand=\"    a &amp;    b\">" +
                "    <selfClosing/>" +
                "  </el>" +
                "</root>");

        // Parse XML to DOM
        Document doc = DomHelper.parse(xml);

        // Convert DOM to terse representation, and convert to JSON
        TerseJson.Options opts = TerseJson.Options
                .with(COMPACT_WHITE_SPACE)
                .and(TerseJson.ErrorBehaviour.ThrowAllErrors);

        Object terseDoc = new TerseJson(opts).convert(doc);
        String json = new Gson().toJson(terseDoc);

        System.out.println(json);
    }
}

produces

[9,[{"1":"root","3":[[8," thïs ïs à cómmënt. "]," ",{"1":"el","2":[["ampersand","    a \u0026    b"]],"3":[" ",{"1":"selfClosing"}," "]}]}]]

Details

JavaDoc

JavaDoc is available at https://digitalheir.github.io/java-xml-to-json/

Node types

var nodeTypes = { 
    1: "element",
    2: "attribute",
    3: "text",
    4: "cdata_section",
    5: "entity_reference",
    6: "entity",
    7: "processing_instruction",
    8: "comment",
    9: "document",
    10: "document_type",
    11: "document_fragment",
    12: "notation"
}

Utility functions

var getChildren = function (node) {
    if (node[0].match(/element|document/) {
        return node[1];
    } else {
        return undefined;
    }
};

var getName = function (node) {
    if (node[0].match(/element/)){
      return node[2];
    } else if(typeof node[0]==="string"){
        return node[0];
    } else{
        return undefined;
    }
}

Document

Translates to a fixed length JSON array:

Element

Translates to a variable length JSON array:

Attribute

Translates to a fixed length JSON array:

Text

Text nodes are converted to JSON strings

Comment

Translates to a fixed length JSON array:

CDATA

Translates to a fixed length JSON array:

Processing instruction

Translates to a fixed length JSON array:

Entity Reference

Not yet implemented

Entity

Not yet implemented

Document type

Not yet implemented

Document fragment

Not yet implemented

Notation

Not yet implemented