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

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.

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

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).