将XML解析为Java对象，需要澄清

Question

What would be the best way to stick this XML into an object?

<root>
    <data value=1>
        <cell a='1' b='0'/>
        <cell a='2' b='0'/>
        <cell a='3' b='0'/>
    </data>
    <data value=12>
        <cell a='2' b='0'/>
        <cell a='4' b='1'/>
        <cell a='3' b='0'/>
    </data>
</root>

We can assume that

• Each data value will be unique.
• Actual numeric value assigned to it is important and needs to be captured
• Actual numbers assigned to data value may come in different order, It won't necessarily be an array of sequential numbers. All we know is that numbers will be unique

Is it possible to put this into Map<Integer, List<Cell>> , grouping cells under the data value ?

Ideally method signature would look as follows public static Map<Integer, List<Cell>> parse(String pathToFile)

Would you provide an example please?

Answer 1

There are lots of examples of XML parsing. The simplest API (definitely not the most efficient) is DOM parsing. Here's one way:

public static Map<Integer, List<Cell>> parse(String pathToFile) {
    DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
    DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
    Document doc = dBuilder.parse(pathToFile);
    Map<Integer, List<Cell>> result = new HashMap<>();
    NodeList dataNodes = doc.getElementsByTagName("data");
    int count = dataNodes.getLength();
    for (int i = 0; i < count; ++i) {
        Node node = dataNodes.item(i);
        if (node.getNodeType() == Node.ELEMENT_NODE) {
            Element element = (Element) node;
            int value = Integer.parseInt(element.getAttribute("value"));
            result.put(value, getCells(element);
        }
    }
    return result;
}

private static List<Cell> getCells(Element dataNode) {
    List<Cell> result = new ArrayList<>();
    NodeList dataNodes = dataNode.getElementsByTagName("cell");
    int count = dataNodes.getLength();
    for (int i = 0; i < count; ++i) {
        // similar to above code
    }
    return result;
}