How to retrieve node after node of XML tree using Xpath?

Question

First, I must say that I find `Xpath` as a very nice parser , and I guess pretty powerful when comparing it to other parsers . Given the following code : ``` DocumentBuilderFactory domFactory = DocumentBuilderFactory.newInstance(); domFactory.setNamespaceAware(true); DocumentBuilder builder = domFactory.newDocumentBuilder(); Document doc = builder.parse("input.xml"); XPath xpath = XPathFactory.newInstance().newXPath(); ``` If I wanted to find the `first` node of Round 1 & Door 1 , here : ``` 1 abd11 0 25 0.31 25 50 0.04 50 75 0.19 75 100 0.46 vvv1133 60 62 1.0 <…

Accepted Answer

Option 1 - Iterate over all Value elements in the document. Only one evaluation required, but difficult to know which Round or Door element the Value belongs to.

```
NodeList result = (NodeList) xpath.evaluate("//Round/Door/Value/*/text()", doc, XPathConstants.NODESET);
```

Option 2 - Iterate over each Round, Door and Value elements separately. Requires more evaluations but the context is easily known. If index is required, it is easy to add a counter to the loops.

```
// Get all rounds and iterate over them
NodeList rounds = (NodeList) xpath.evaluate("//Round", doc, XPathConstants.NODESET);
for (Node round : rounds) {
  // Get all doors and iterate over them
  NodeList doors = (NodeList) xpath.evaluate("Door", round, XPathConstants.NODESET);
  for (Node door : doors) {
    // Get all values and iterate over them
    NodeList values = (NodeList) xpath.evaluate("Value/*/text()", door, XPathConstants.NODESET);
    for (Node value : values) {
      // Do something
    }
  }
}
```

Option 3 - Do some combination of the above depending on your requirements

Note that I've removed the expression compilation step to shorten the example. It should be re-added to improve performance.

How to retrieve node after node of XML tree using Xpath?

Solution

Problem