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xml-xsd-json

XML Schema visualization and XML Schema based XML <-> JSON conversion

XML Schema Visualization

The com.mcsuka.xml.xsd package implements an XML Schema parser. It converts an XSD file (or a number of related XSD files) to a simple tree of 'SchemaNode' objects. Each SchemaNode represents one of the following:

  • an element: xsd:element or xsd:any
  • an attribute: xsd:attribute or xsd:anyAttribute
  • an indicator: xsd:sequence xsd:all or xsd:choice

Each SchemaNode has the following properties:

  • elementName - the localName of an element or attribute, '' for an indicator, '*' for an any element or attribute
  • namespace - name space of the element or attribute
  • indicator - type of indicator, for indicator nodes
  • defaultValue default value of the element or attribute, null if there is no default value. If no default value is defined then a dummy default value is assigned to every simple type, to allow auto-generation of the XML element
  • fixedValue fixed value of the element or attribute, null if there is no default value
  • minOccurs minimum occurrence of the element, attribute or indicator
  • maxOccurs maximum occurrence of the element, attribute or indicator. Integer.MAX_VALUE is used to define 'unbounded'
  • flags to define a boolean property of the SchemaNode:
    • qualified - whether the element or attribute should be placed in its name space
    • attribute - whether it is an attribute
    • any - whether it is an "any" type
  • w3cType - the basic type of the element or attribute, or COMPLEX/MIXED for complex types
  • customType - the localName of the explicitly defined type
  • documentation - annotation/documentation of the element or type
  • restrictions - restrictions applied on the type, in human-readable format

The XML schema can be visualized as a text document using the dumpTree() convenience function of the SchemaNode class. Other visualizations (HTML, graphic, ...) can be easily implemented as separate classes.

XML to JSON translation

The com.mcsuka.xml.json package implements an XML/JSON translator, using the GSON, Xerces and Saxon-HE libraries. Translation may or may not use an XML Schema. Using an XML schema has the following advantages:

  • keep types: the resulting JSON will contain boolean and numeric values without quotes
  • keep arrays: the resulting JSON will contain array for keys that are defined as repeatable elements in the XSD, even if there is only one element in the input XML.
    • please note, you may also use the _jsonarray="true" attribute in the input XML to force array creation

Disadvantage of using an XML Schema:

  • slightly slower translation

JSON to XML translation

The com.mcsuka.xml.json package implements a JSON/XML translator, using the GSON, Xerces and Saxon-HE libraries. Translation may or may not use an XML Schema. Using an XML schema has the following advantages:

  • add correct name space to the elements and attributes
  • correct the order of the elements for 'sequence' indicator
  • create missing, mandatory elements and attributes:
    • missing elements and attributes are created with their fixed or default values. If there is no default value defined, a dummy value is chosen, according to the data type
  • remove invalid elements:
    • not in the schema
    • over the 'maxOccurs' limit
    • multiple elements inside a choice indicator

Disadvantage of using an XML Schema:

  • slightly slower translation

JSON to XML translation will modify the JSON keys that are not XML element-name compatible. All non-compatible characters will be replaced with an underscore character. Please note, there is no guarantee that the XML produced by the translator is valid (to the schema).