How to use StaX

Question

Hey guys so I am brand new to the world of Java-XML parsing and found that the StaX API is probably my best bet as I need to both read and write XML files. Alright so I have a very short (and should be very simple) program that (should) create an XMLInputFactory and use that to create a XMLStreamReader. The XMLStreamReader is created using a FileInputStream attached to an XML file in the same directory as the source file. However even though the FileInputStream compiled properly, the XMLInputFactory cannot access it and without the FileInputStream it cannot creat the XMLStreamReader. Please help as I have no idea what to and am frustrated to the point of giving up!

import javax.xml.stream.*;
import java.io.*;
public class xml {
    static String status;
    public static void main(String[] args) {
        status = "Program has started";
        printStatus();      
        XMLInputFactory inFactory = XMLInputFactory.newInstance();
            status = "XMLInputFactory (inFactory) defined"; printStatus();
        try { FileInputStream fIS = new FileInputStream("stax.xml"); }
            catch (FileNotFoundException na) { System.out.println("FileNotFound"); }
            status = "InputStream (fIS) declared"; printStatus();
        try { XMLStreamReader xmlReader = inFactory.createXMLStreamReader(fIS); } catch (XMLStreamException xmle) { System.out.println(xmle); }
            status = "XMLStreamReader (xmlReader) created by 'inFactory'"; printStatus();
    }
    public static void printStatus(){ //this is a little code that send notifications when something has been done
        System.out.println("Status: " + status);
    }
}

also here is the XML file if you need it:

<?xml version="1.0"?>
    <dennis>
        <hair>brown</hair>
        <pants>blue</pants>
        <gender>male</gender>
    </dennis>

Answer 1

Your problem has to do w/ basic java programming, nothing to do w/ stax. your FileInputStream is scoped within a try block (some decent code formatting would help) and therefore not visible to the code where you are attempting to create the XMLStreamReader. with formatting:

    XMLInputFactory inFactory = XMLInputFactory.newInstance();
    try {
        // fIS is only visible within this try{} block
        FileInputStream fIS = new FileInputStream("stax.xml");
    } catch (FileNotFoundException na) {
        System.out.println("FileNotFound");
    }
    try {
        // fIS is not visible here
        XMLStreamReader xmlReader = inFactory.createXMLStreamReader(fIS);
    } catch (XMLStreamException xmle) {
        System.out.println(xmle);
    }

on a secondary note, StAX is a nice API, and a great one for highly performant XML processing in java. however, it is not the simplest XML api. you would probably be better off starting with the DOM based apis, and only using StAX if you experience performance issues using DOM. if you do stay with StAX, i'd advise using XMLEventReader instead of XMLStreamReader (again, an easier api).

lastly, do not hide exception details (e.g. catch them and print out something which does not include the exception itself) or ignore them (e.g. continue processing after the exception is thrown without attempting to deal with the problem).