Extracting Values From an XML File Either using XPath, SAX or DOM for this Specific Scenario

Question

I am currently working on an academic project, developing in Java and XML. Actual task is to parse XML, passing required values preferably in HashMap for further processing. Here is the short snippet of actual XML.

<root>
  <BugReport ID = "1">
    <Title>"(495584) Firefox - search suggestions passes wrong previous result to form history"</Title>

    <Turn>
      <Date>'2009-06-14 18:55:25'</Date>
      <From>'Justin Dolske'</From>
      <Text>
        <Sentence ID = "3.1"> Created an attachment (id=383211) [details] Patch v.2</Sentence>
        <Sentence ID = "3.2"> Ah. So, there's a ._formHistoryResult in the....</Sentence>
        <Sentence ID = "3.3"> The simple fix it to just discard the service's form history result.</Sentence>
        <Sentence ID = "3.4"> Otherwise it's trying to use a old form history result that no longer applies for the search string.</Sentence>
      </Text>
    </Turn>

    <Turn>
      <Date>'2009-06-19 12:07:34'</Date>
      <From>'Gavin Sharp'</From>
      <Text>
        <Sentence ID = "4.1"> (From update of attachment 383211 [details])</Sentence>
        <Sentence ID = "4.2"> Perhaps we should rename one of them to _fhResult just to reduce confusion?</Sentence>
      </Text>
    </Turn>

    <Turn>
      <Date>'2009-06-19 13:17:56'</Date>
      <From>'Justin Dolske'</From>
      <Text>
        <Sentence ID = "5.1"> (In reply to comment #3)</Sentence>
        <Sentence ID = "5.2"> &amp;gt; (From update of attachment 383211 [details] [details])</Sentence> 
        <Sentence ID = "5.3"> &amp;gt; Perhaps we should rename one of them to _fhResult just to reduce confusion?</Sentence>
        <Sentence ID = "5.4"> Good point.</Sentence>
        <Sentence ID = "5.5"> I renamed the one in the wrapper to _formHistResult. </Sentence>
        <Sentence ID = "5.6"> fhResult seemed maybe a bit too short.</Sentence>
      </Text>
    </Turn>

  .....
  and so on
</BugReport>

There are many commenter like 'Justin Dolske' who have commented on this report and what I actually looking for is the list of commenter and all sentences they have written in a whole XML file. Something like if(from == justin dolske) getHisAllSentences(). Similarly for other commenters (for all). I have tried many different ways to get the sentences only for 'Justin dolske' or other commenters, even in a generic form for all using XPath, SAX and DOM but failed. I am quite new to these technologies including JAVA and any don't know how to achieve it.

Can anyone guide me specifically how could I get it with any of above technologies or is there any other better strategy to do it?

(Note: Later I want to put it in a hashmap such as like this HashMap (key, value) where key = name of commenter (justin dolske) and value is (all sentences))

Urgent help will be highly appreciated.

Answer 1

There're several ways using which you can achieve your requirement.

• One way would be use JAXB. There're several tutorials available on this on the web, so feel free to refer to them.

• You can also think of creating a DOM and then extracting data from it and then put it into your HashMap.

One reference implementation would be something like this:

import java.io.File;
import java.util.ArrayList;
import java.util.HashMap;

import javax.xml.parsers.DocumentBuilderFactory;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;

public class XMLReader {

    private HashMap<String,ArrayList<String>> namesSentencesMap;

    public XMLReader() {
        namesSentencesMap = new HashMap<String, ArrayList<String>>();
    }

    private Document getDocument(String fileName){
        Document document = null;

        try{
            document = DocumentBuilderFactory.newInstance().newDocumentBuilder().parse(new File(fileName));
        }catch(Exception exe){
            //handle exception
        }

        return document;
    }

    private void buildNamesSentencesMap(Document document){
        if(document == null){
            return;
        }

        //Get each Turn block
        NodeList turnList = document.getElementsByTagName("Turn");
        String fromName = null;

        NodeList sentenceNodeList = null;
        for(int turnIndex = 0; turnIndex < turnList.getLength(); turnIndex++){
            Element turnElement = (Element)turnList.item(turnIndex);
            //Assumption: <From> element
            Element fromElement = (Element) turnElement.getElementsByTagName("From").item(0); 
            fromName = fromElement.getTextContent();
            //Extracting sentences - First check whether the map contains 
            //an ArrayList corresponding to the name. If yes, then use that,  
            //else create a new one                                              
            ArrayList<String> sentenceList = namesSentencesMap.get(fromName);
            if(sentenceList == null){
                sentenceList = new ArrayList<String>();
            }
            //Extract sentences from the Turn node
            try{
                sentenceNodeList = turnElement.getElementsByTagName("Sentence");
                for(int sentenceIndex = 0; sentenceIndex < sentenceNodeList.getLength(); sentenceIndex++){
                    sentenceList.add(((Element)sentenceNodeList.item(sentenceIndex)).getTextContent());
                }
            }finally{
                sentenceNodeList = null;
            }
            //Put the list back in the map                  
            namesSentencesMap.put(fromName, sentenceList);
        }
    }

    public static void main(String[] args) {
        XMLReader reader = new XMLReader();
        reader.buildNamesSentencesMap(reader.getDocument("<your_xml_file>"));

        for(String names: reader.namesSentencesMap.keySet()){
            System.out.println("Name: "+names+"\tTotal Sentences: "+reader.namesSentencesMap.get(names).size());
        }
    }
}

Note: This is just a demonstration and you would need to modify it to suit your need. I've created it based on your XML to show one way of doing it.

Answer 2

I suggest to use JAXB to creates a Data Model reflecting your XML structure.

One done, you can load the XML into Java instances.

Put each 'Turn' into a Map< String, List< Turn >>, using Turn.From as key.

Once done, you'll can write:

List< Turn > justinsTurn = allTurns.get( "'Justin Dolske'" );