SimpleXmlGenerator

/**
* fieldIdentifier = //ROOT/FOO[0], fieldValue = abc
* fieldIdentifier = //ROOT/FOO[1]/@Bar, fieldValue = xyz
*/

public class SimpleXmlGenerator {

    public static String createXml(String xmlRootName, List<FieldEnumeration> inputFields) {
        StringBuilder xmlString = new StringBuilder("<?xml version=\"1.0\" encoding=\"UTF-8\"?>");
        buildXml(xmlString, buildXmlNodes(xmlRootName, inputFields));
        return xmlString.toString();
    }

    public static String createXml(XmlNode xmlNode) {
        StringBuilder xmlString = new StringBuilder("<?xml version=\"1.0\" encoding=\"UTF-8\"?>");
        buildXml(xmlString, xmlNode);
        return xmlString.toString();
    }

    private static XmlNode buildXmlNodes(String xmlRootName, List<FieldEnumeration> inputFields) {
        XmlNode rootNode = new XmlNode(xmlRootName);

        inputFields.forEach(p -> {
            XmlNode previousNode = rootNode;
            for (String node : p.getFieldIdentifier().replaceAll("//", "").split("\\/")) {
                XmlNode childNode;
                if (node.startsWith("@")) {
                    childNode = new XmlNode(node.replaceAll("@", ""), p.getFieldValue());
                    childNode.setAttribute(true);
                    childNode.setParent(previousNode.getName());
                    previousNode.addAttribute(childNode);
                } else {
                    Optional<XmlNode> optionalChild = previousNode.findNode(node);
                    if (optionalChild.isPresent()) {
                        childNode = optionalChild.get();
                    } else {
                        childNode = new XmlNode(node);
                        previousNode.addChild(childNode);
                    }
                }
                previousNode = childNode;
            }

            if (!previousNode.isAttribute()) {
                previousNode.setValue(p.getFieldValue());
            }
        });

        return rootNode;
    }

    private static void buildXml(StringBuilder xmlString, XmlNode xmlNode) {
        final String strippedNodeName = xmlNode.getName().replaceAll("\\[[\\d]\\]", "");
        xmlString.append("<").append(strippedNodeName);

        if (xmlNode.hasAttributes()) {
            xmlNode.getAttributes().forEach(n -> xmlString.append(" ").append(n.getName()).append("=").append("\"").append(n.getValue()).append("\""));
        }

        if (xmlNode.hasChildren()) {
            xmlString.append(">");
            xmlNode.getChildren().forEach(c -> buildXml(xmlString, c));
            xmlString.append("</").append(strippedNodeName).append(">");
        } else {
            if (Objects.nonNull(xmlNode.getValue())) {
                xmlString.append(">").append(xmlNode.getValue()).append("</").append(strippedNodeName).append(">");
            } else {
                xmlString.append("/>");
            }
        }
    }
}

public class XmlNode {

    private String name;
    private String parent;
    private String value;
    private boolean isAttribute;
    private List<XmlNode> children;
    private List<XmlNode> attributes;

    public XmlNode(String name) {
        this.name = name;
        this.isAttribute = false;
        this.children = new ArrayList<>();
        this.attributes = new ArrayList<>();
    }

    public XmlNode(String name, String value) {
        this(name);
        this.value = value;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getParent() {
        return parent;
    }

    public void setParent(String parent) {
        this.parent = parent;
    }

    public String getValue() {
        return value;
    }

    public void setValue(String value) {
        this.value = value;
    }

    public boolean isAttribute() {
        return isAttribute;
    }

    public void setAttribute(boolean attribute) {
        isAttribute = attribute;
    }

    public List<XmlNode> getChildren() {
        return children;
    }

    public void setChildren(List<XmlNode> children) {
        this.children = children;
    }

    public List<XmlNode> getAttributes() {
        return attributes;
    }

    public void setAttributes(List<XmlNode> attributes) {
        this.attributes = attributes;
    }

    public void addChild(XmlNode childNode) {
        this.children.add(childNode);
    }

    public void addAttribute(XmlNode attributeNode) {
        this.attributes.add(attributeNode);
    }

    public Optional<XmlNode> findNode(String nodeName) {
        if (nodeName.equals(this.getName())) {
            return Optional.of(this);
        }
        return getChildren().stream().filter(n -> nodeName.equals(n.getName())).findFirst();
    }


    public boolean hasChildren() {
        return !getChildren().isEmpty();
    }

    public boolean hasAttributes() {
        return !getAttributes().isEmpty();
    }
}