XMLParsing, Dynamic Structure, Content

Question

Want to Achive:

Get an unknown XML file's Elements (Element Name, How many elements are there in the xml file).

Then get all the attributes and their name and values to use it later (eg Comparison to other xml file)

element_vs_attribute

Researched: 1. 2. 3. 4. 5. And many more

Does Anyone have any idea for this?

I dont want to pre define more then 500 table like in the previous code snippet, somehow i should be able to get the number of elements and the element names itself dynamically.

EDIT!

Example1
<Root Attri1="" Attri2="">
    <element1 EAttri1="" EAttri2=""/>
    <Element2 EAttri1="" EAttri2="">
        <nestedelement3 NEAttri1="" NEAttri2=""/>
    </Element2> 
</Root>

Example2
<Root Attri1="" Attri2="" Attr="" At="">
    <element1 EAttri1="" EAttri2="">
        <nestedElement2 EAttri1="" EAttri2="">
            <nestedelement3 NEAttri1="" NEAttri2=""/>
        </nestedElement2>
    </element1> 
</Root>

Program Snipet:

String Example1[] = {"element1","Element2","nestedelement3"};
String Example2[] = {"element1","nestedElement2","nestedelement3"};


for(int i=0;i<Example1.length;++){
    NodeList Elements = oldDOC.getElementsByTagName(Example1[i]);
    for(int j=0;j<Elements.getLength();j++) {
        Node nodeinfo=Elements.item(j);
        for(int l=0;l<nodeinfo.getAttributes().getLength();l++) {
        .....
    }
}

Output: The expected result is to get all the Element and all the Attributes out from the XML file without pre defining anything.

eg:

Elements: element1 Element2 nestedelement3

Attributes:  Attri1 Attri2 EAttri1 EAttri2 EAttri1 EAttri2 NEAttri1 NEAttri2

Answer 1

The right tool for this job is xpath It allows you to collect all or some elements and attributes based on various criteria. It is the closest you will get to a "universal" xml parser.

Here is the solution that I came up with. The solution first finds all element names in the given xml doc, then for each element, it counts the element's occurrences, then collect it all to a map. same for attributes.
I added inline comments and method/variable names should be self explanatory.

import java.io.*;
import java.nio.file.*;
import java.util.*;
import java.util.function.*;
import java.util.stream.*;

import org.w3c.dom.*;

import javax.xml.parsers.*;
import javax.xml.xpath.*;

public class TestXpath
{

    public static void main(String[] args) {

        XPath xPath = XPathFactory.newInstance().newXPath();

        try (InputStream is = Files.newInputStream(Paths.get("C://temp/test.xml"))) {
            // parse file into xml doc
            DocumentBuilder builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
            Document xmlDocument = builder.parse(is);

            // find all element names in xml doc
            Set<String> allElementNames = findNames(xmlDocument, xPath.compile("//*[name()]"));
            // for each name, count occurrences, and collect to map
            Map<String, Integer> elementsAndOccurrences = allElementNames.stream()
                .collect(Collectors.toMap(Function.identity(), name -> countElementOccurrences(xmlDocument, name)));
            System.out.println(elementsAndOccurrences);

            // find all attribute names in xml doc
            Set<String> allAttributeNames = findNames(xmlDocument, xPath.compile("//@*"));
            // for each name, count occurrences, and collect to map
            Map<String, Integer> attributesAndOccurrences = allAttributeNames.stream()
                .collect(Collectors.toMap(Function.identity(), name -> countAttributeOccurrences(xmlDocument, name)));
            System.out.println(attributesAndOccurrences);

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static Set<String> findNames(Document xmlDoc, XPathExpression xpathExpr) {
        try {
            NodeList nodeList = (NodeList)xpathExpr.evaluate(xmlDoc, XPathConstants.NODESET);
            // convert nodeList to set of node names
            return IntStream.range(0, nodeList.getLength())
                .mapToObj(i -> nodeList.item(i).getNodeName())
                .collect(Collectors.toSet());
        } catch (XPathExpressionException e) {
            e.printStackTrace();
        }
        return new HashSet<>();
    }

    public static int countElementOccurrences(Document xmlDoc, String elementName) {
        return countOccurrences(xmlDoc, elementName, "count(//*[name()='" + elementName + "'])");
    }

    public static int countAttributeOccurrences(Document xmlDoc, String attributeName) {
        return countOccurrences(xmlDoc, attributeName, "count(//@*[name()='" + attributeName + "'])");
    }

    public static int countOccurrences(Document xmlDoc, String name, String xpathExpr) {
        XPath xPath = XPathFactory.newInstance().newXPath();
        try {
            Number count = (Number)xPath.compile(xpathExpr).evaluate(xmlDoc, XPathConstants.NUMBER);
            return count.intValue();
        } catch (XPathExpressionException e) {
            e.printStackTrace();
        }
        return 0;
    }
}