Question

I’m trying to read XML file, ex :

<entry>
    <title>FEED TITLE</title>
    <id>5467sdad98787ad3149878sasda</id>
    <tempi type="application/xml">
      <conento xmlns="http://mydomainname.com/xsd/radiofeed.xsd" madeIn="USA" />
    </tempi>
</entry>

Here is the code I have so far: http://pastebin.com/huKP4KED

Here is what I need, concerning XML above:

• I need to get value of title, id
• attribute value of tempi as well as madeIn attribute value of contento

What is the best way to do this ?

Edit

@Pascal Thivent

Maybe creating method would be good idea like public String getValue(String xml, Element elementname), where you specify tag name, the method returns tag value or tag attribute (maybe give it name as additional method argument) if the value is not available

What I really want to get certain tag value or attribute if tag value(s) is not available, so I’m in the process of thinking what is the best way to do so since I’ve never done it before.

Answer 1

The best solution for this is to use XPath. Let’s say we have the following feed.xml file:

<?xml version="1.0" encoding="UTF-8" ?>
<entries>
<entry>
    <title>FEED TITLE 1</title>
    <id>id1</id>
    <tempi type="type1">
      <conento xmlns="dontcare?" madeIn="MadeIn1" />
    </tempi>
</entry>
<entry>
    <title>FEED TITLE 2</title>
    <id>id2</id>
    <tempi type="type2">
      <conento xmlns="dontcare?" madeIn="MadeIn2" />
    </tempi>
</entry>
<entry>
    <id>id3</id>
</entry>
</entries>

Here’s a short but compile-and-runnable proof-of-concept (with feed.xml file in the same directory).

import javax.xml.xpath.*;
import javax.xml.parsers.*;
import org.w3c.dom.*;
import java.io.*;
import java.util.*;

public class XPathTest {
    static class Entry {
        final String title, id, origin, type;
        Entry(String title, String id, String origin, String type) {
            this.title = title;
            this.id = id;
            this.origin = origin;
            this.type = type;
        }
        @Override public String toString() {
            return String.format("%s:%s(%s)[%s]", id, title, origin, type);
        }
    }

    final static XPath xpath = XPathFactory.newInstance().newXPath();
    static String evalString(Node context, String path) throws XPathExpressionException {
        return (String) xpath.evaluate(path, context, XPathConstants.STRING);
    }

    public static void main(String[] args) throws Exception {
        File file = new File("feed.xml");
        Document document = DocumentBuilderFactory.newInstance().newDocumentBuilder().parse(file);
        NodeList entriesNodeList = (NodeList) xpath.evaluate("//entry", document, XPathConstants.NODESET);

        List<Entry> entries = new ArrayList<Entry>();
        for (int i = 0; i < entriesNodeList.getLength(); i++) {
            Node entryNode = entriesNodeList.item(i);
            entries.add(new Entry(
                evalString(entryNode, "title"),
                evalString(entryNode, "id"),
                evalString(entryNode, "tempi/conento/@madeIn"),
                evalString(entryNode, "tempi/@type")
            ));
        }
        for (Entry entry : entries) {
            System.out.println(entry);
        }
    }
}

This produces the following output:

id1:FEED TITLE 1(MadeIn1)[type1]
id2:FEED TITLE 2(MadeIn2)[type2]
id3:()[]

Note how using XPath makes the value retrieval very simple, intuitive, readable, and straightforward, and "missing" values are also gracefully handled.

API links

• package javax.xml.xpath
• http://www.w3.org/TR/xpath
• Wikipedia/XPath