Example processing a simple XML schema in SAX and generating a tree

SAX XML Schema processing

public class SAXReaderExample {
    
    public static final String PATH = "/tmp/resources";

    public static void main(String[] args) throws ParserConfigurationException, SAXException, IOException {
        SAXParserFactory spf = SAXParserFactory.newInstance();
        SAXParser sp = spf.newSAXParser();
        XMLReader reader = sp.getXMLReader();
        reader.setContentHandler(new SchemaSaxHandler());
        reader.parse(new InputSource(new FileInputStream(new File(PATH, "source.xsd"))));
    }
}

class SchemaElement {
    
    private String name;
    private String type;
    private List<SchemaElement> children;
    private Map<String, String> attributes;
    
    // getters and setters
}

class SchemaComplexType {
    
    private String name;
    private List<SchemaElement> children;
    private Map<String, String> attributes = new HashMap<>();
    
    // getters and setters + addAttribute
}

class SchemaSaxHandler extends DefaultHandler {

    // temporary - always null when tag closes
    private String currentSimpleTypeName;
    private String currentSimpleTypeBaseType;
    private SchemaElement currentElement;
    private SchemaComplexType currentComplexType;
    private List<SchemaElement> currentSequence;

    // cumulative - will use the data when XML finishes
    private Map<String, String> simpleTypes = new HashMap<>();
    private Map<String, SchemaComplexType> complexTypes = new HashMap<>();
    private SchemaElement rootElement;

    @Override
    public void startElement(String uri, String localName, String qName, Attributes atts) throws SAXException {

        if (qName.equals("xs:simpleType")) {
            currentSimpleTypeName = atts.getValue("name");
        }
        if (qName.equals("xs:restriction")) {
            currentSimpleTypeBaseType = atts.getValue("base");
        }

        if (qName.equals("xs:complexType")) {
            currentComplexType = new SchemaComplexType();
            currentComplexType.setName(atts.getValue("name"));
        }

        if (qName.equals("xs:sequence")) {
            currentSequence = new ArrayList<>();
        }

        if (qName.equals("xs:element")) {
            currentElement = new SchemaElement();
            currentElement.setName(atts.getValue("name"));
            currentElement.setType(atts.getValue("type"));
            if (currentSequence != null) {
                currentSequence.add(currentElement);
            } else {
                rootElement = currentElement;
            }
        }

        if (qName.equals("xs:attribute")) {
            currentComplexType.addAttribute(atts.getValue("name"), atts.getValue("type"));
        }
    }

    @Override
    public void endElement(String uri, String localName, String qName) throws SAXException {
        if (qName.equals("xs:simpleType")) {
            simpleTypes.put(currentSimpleTypeName, currentSimpleTypeBaseType);
            currentSimpleTypeName = null;
            currentSimpleTypeBaseType = null;
        }
        if (qName.equals("xs:complexType")) {
            complexTypes.put(currentComplexType.getName(), currentComplexType);
            currentComplexType = null;
        }
        if (qName.equals("xs:sequence")) {
            if (currentComplexType != null) {
                currentComplexType.setChildren(currentSequence);
            }
            currentSequence = null;
        }
    }

    @Override
    public void endDocument() throws SAXException {
        makeTree(rootElement);
        printTree(rootElement, "");
    }

    public void makeTree(SchemaElement element) {
        SchemaComplexType type = complexTypes.get(element.getType());
        if (type != null) {
            List<SchemaElement> children = type.getChildren();
            element.setChildren(children);
            for (SchemaElement child : children) {
                makeTree(child);
            }
            element.setAttributes(type.getAttributes());
        } else {
            element.setType(simpleTypes.get(element.getType()));
        }
    }

    private void printTree(SchemaElement element, String indent) {
        System.out.println(indent + element.getName() + " : " + element.getType());
        Map<String, String> attributes = element.getAttributes();
        if (attributes != null) {
            for (Map.Entry<String, String> entry : attributes.entrySet()) {
                System.out.println("    @" + entry.getKey() + " : " + simpleTypes.get(entry.getValue()));
            }
        }
        List<SchemaElement> children = element.getChildren();
        if (children != null) {
            for (SchemaElement child : children) {
                printTree(child, indent + "    ");
            }
        }
    }

}

Hey .. i am really interested in parsing XML Schema the way you did .. but it didn't gave me the result obtained with the example here https://stackoverflow.com/questions/21527978/parsing-xsd-to-tree-structure .. i want to know why ?