How to parse XML using the SAX parser

Question

I\'m following this tutorial.

It works great but I would like it to return an array with all the strings instead of a single string with the last element.

An

Answer 1

In many problems it is necessary to use different kinds of xml files for different purposes. I will not attempt to grasp the immensity and tell from my own experience what I needed all this.

Java, perhaps, my favorite programming language. In addition, this love is strengthened by the fact that you can solve any problem and come up with a bike is not necessary.

So, it took me to create a bunch of client-server running a database that would allow the client to remotely make entries in the database server. Needless to be checking input data, etc. and the like, but it's not about that.

As a principle of work, I, without hesitation, chose the transmission of information in the form of xml file. Of the following types:

 
 
 3  
 Ivanov  
 Ivan  
 I.  
 10-03-2005  
 10-03-2005  
 10-03-2005  
 09-06-2009  
 10-03-2005  
 1  
 1  
 1  
 2.0  
 1  
 

Make it easier to read any further, except to say that it is the information about doctors institutions. Last name, first name, unique id, and so on. In general, the data series. This file safely got on the server side, and then start parsing the file.

Of the two options parsing (SAX vs DOM) I chose SAX view of the fact that he works more bright, and he was the first I fell into the hands :)

So. As you know, to work successfully with the parser, we need to override the needed methods DefaultHandler's. To begin, connect the required packages.

import org.xml.sax.helpers.DefaultHandler; 
import org.xml.sax. *; 

Now we can start writing our parser

public class SAXPars extends DefaultHandler {
   ... 
} 

Let's start with the method startDocument (). He, as the name implies, reacts to an event beginning of the document. Here you can hang a variety of actions such as memory allocation, or to reset the values​​, but our example is pretty simple, so just mark the beginning of work of an appropriate message:

Override 
public void startDocument () throws SAXException {
   System.out.println ("Start parse XML ..."); 
} 

Next. The parser goes through the document meets the element of its structure. Starts method startElement (). And in fact, his appearance this: startElement (String namespaceURI, String localName, String qName, Attributes atts). Here namespaceURI - the namespace, localName - the local name of the element, qName- a combination of local name with a namespace (separated by a colon) and atts - the attributes of this element. In this case, all simple. It suffices to use qName'om and throw it into some service line thisElement. Thus we mark in which the element at the moment we are.

@Override 
public void startElement (String namespaceURI, String localName, String qName, Attributes atts) throws SAXException {
   thisElement = qName; 
} 

Next, meeting item we get to its meaning. Here include methods characters (). He has the form: characters (char [] ch, int start, int length). Well here everything is clear. ch - a file containing the string itself self-importance within this element. start and length - the number of service indicating the starting point in the line and length.

@Override 
public void characters (char [] ch, int start, int length) throws SAXException {
   if (thisElement.equals ("id")) {
      doc.setId (new Integer (new String (ch, start, length))); 
   } 
   if (thisElement.equals ("fam")) {
      doc.setFam (new String (ch, start, length)); 
   } 
   if (thisElement.equals ("name")) {
      doc.setName (new String (ch, start, length)); 
   } 
   if (thisElement.equals ("otc")) {
      doc.setOtc (new String (ch, start, length)); 
   } 
   if (thisElement.equals ("dateb")) {
      doc.setDateb (new String (ch, start, length)); 
   } 
   if (thisElement.equals ("datep")) {
      doc.setDatep (new String (ch, start, length)); 
   } 
   if (thisElement.equals ("datev")) {
      doc.setDatev (new String (ch, start, length)); 
   } 
   if (thisElement.equals ("datebegin")) {
      doc.setDatebegin (new String (ch, start, length)); 
   } 
   if (thisElement.equals ("dateend")) {
      doc.setDateend (new String (ch, start, length)); 
   } 
   if (thisElement.equals ("vdolid")) {
      doc.setVdolid (new Integer (new String (ch, start, length))); 
   } 
   if (thisElement.equals ("specid")) {
      doc.setSpecid (new Integer (new String (ch, start, length))); 
   } 
   if (thisElement.equals ("klavid")) {
      doc.setKlavid (new Integer (new String (ch, start, length))); 
   } 
   if (thisElement.equals ("stav")) {
      doc.setStav (new Float (new String (ch, start, length))); 
   } 
   if (thisElement.equals ("progid")) {
      doc.setProgid (new Integer (new String (ch, start, length))); 
   } 
} 

Ah, yes. I almost forgot. As the object of which will be to fold naparsennye data speaks to the type of Doctors. This class is defined and has all the necessary setters-getters.

Next obvious element ends and it is followed by the next. Responsible for ending the endElement (). It signals to us that the item has ended and you can do anything at this time. Will proceed. Cleanse Element.

@Override 
public void endElement (String namespaceURI, String localName, String qName) throws SAXException {
   thisElement = ""; 
} 

Coming so the entire document, we come to the end of the file. Work endDocument (). In it, we can free up memory, do some diagnostichesuyu printing, etc. In our case, just write about what parsing ends.

@Override 
public void endDocument () {
   System.out.println ("Stop parse XML ..."); 
} 

So we got a class to parse xml our format. Here is the full text:

import org.xml.sax.helpers.DefaultHandler; 
import org.xml.sax. *; 
 
public class SAXPars extends DefaultHandler {
 
Doctors doc = new Doctors (); 
String thisElement = ""; 
 
public Doctors getResult () {
   return doc; 
} 
 
@Override 
public void startDocument () throws SAXException {
   System.out.println ("Start parse XML ..."); 
} 
 
@Override 
public void startElement (String namespaceURI, String localName, String qName, Attributes atts) throws SAXException {
   thisElement = qName; 
} 
 
@Override 
public void endElement (String namespaceURI, String localName, String qName) throws SAXException {
   thisElement = ""; 
} 
 
@Override 
public void characters (char [] ch, int start, int length) throws SAXException {
   if (thisElement.equals ("id")) {
      doc.setId (new Integer (new String (ch, start, length))); 
   } 
   if (thisElement.equals ("fam")) {
      doc.setFam (new String (ch, start, length)); 
   } 
   if (thisElement.equals ("name")) {
      doc.setName (new String (ch, start, length)); 
   } 
   if (thisElement.equals ("otc")) {
      doc.setOtc (new String (ch, start, length)); 
   } 
   if (thisElement.equals ("dateb")) {
      doc.setDateb (new String (ch, start, length)); 
   } 
   if (thisElement.equals ("datep")) {
      doc.setDatep (new String (ch, start, length)); 
   } 
   if (thisElement.equals ("datev")) {
      doc.setDatev (new String (ch, start, length)); 
   } 
   if (thisElement.equals ("datebegin")) {
      doc.setDatebegin (new String (ch, start, length)); 
   } 
   if (thisElement.equals ("dateend")) {
      doc.setDateend (new String (ch, start, length)); 
   } 
   if (thisElement.equals ("vdolid")) {
      doc.setVdolid (new Integer (new String (ch, start, length))); 
   } 
   if (thisElement.equals ("specid")) {
      doc.setSpecid (new Integer (new String (ch, start, length))); 
   } 
   if (thisElement.equals ("klavid")) {
      doc.setKlavid (new Integer (new String (ch, start, length))); 
   } 
   if (thisElement.equals ("stav")) {
      doc.setStav (new Float (new String (ch, start, length))); 
   } 
   if (thisElement.equals ("progid")) {
      doc.setProgid (new Integer (new String (ch, start, length))); 
   } 
} 
 
@Override 
public void endDocument () {
   System.out.println ("Stop parse XML ..."); 
} 
} 

I hope the topic helped to easily present the essence of the SAX parser.

Do not judge strictly first article :) I hope it was at least someone useful.

UPD: To run this parser, you can use this code:

SAXParserFactory factory = SAXParserFactory.newInstance (); 
SAXParser parser = factory.newSAXParser (); 
SAXPars saxp = new SAXPars (); 
 
parser.parse (new File ("..."), saxp); 

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