Parse xml file using vtd-xml

Question

How can i parse a xml file like the following using vtd-xml in java or C ?

Answer 1

I guess some of this depends on how you want to parse the file.

Here's a "non-production" example which uses a few techniques which are useful, including:

• XPath select (just using "/*" here)
• look through all sibling nodes
• look down through child nodes
• extract node attributes into a map using AutoPilot

Hope it helps

package scce;

import com.ximpleware.AutoPilot;
import com.ximpleware.NavException;
import com.ximpleware.VTDGen;
import com.ximpleware.VTDNav;
import com.ximpleware.XPathEvalException;
import com.ximpleware.XPathParseException;
import java.io.File;
import java.io.IOException;
import java.util.LinkedHashMap;
import java.util.Map;

/**
 *
 * @author David
 */
public class VTDParserExample {

    VTDGen vg;
    VTDNav vn;

    public VTDParserExample() {
        vg = new VTDGen();    
    }

    public void parseAndPrint() throws NavException {

        int level = 0;

        for(boolean el = (vn != null); 
                    el == true ;
                    el = vn.toElement(VTDNav.NEXT_SIBLING)) {

            printTag(vn, level);

            parseAndPrintChildren(level);                
        }

    } 

     private void parseAndPrintChildren(int level) throws NavException {

        vn.push();

        for(boolean el = vn.toElement(VTDNav.FIRST_CHILD); 
                    el == true ;
                    el = vn.toElement(VTDNav.NEXT_SIBLING)) {

            printTag(vn, level + 1);

            parseAndPrintChildren(level + 1);                
        }

        vn.pop();

    }

    public VTDNav loadFile(String filePath) throws IOException {

        File fDoc = new File(filePath);

        if (fDoc != null && fDoc.exists()) {
            System.out.println("loadFile file exists ["+filePath+"]");

            vg.clear();
            if (vg.parseFile(filePath, true)) {
                vn = vg.getNav();
            }
        }
        else {
            throw new IOException("File ["+filePath+"] invalid");
        }             

        if (vn == null) {                
            throw new IOException("Cannot parse file ["+filePath+"]");
        }

        return vn;
    }

    public void getElementsByXpath() {

        AutoPilot ap = new AutoPilot(vn);

        try
        {
            String xpQ = "/*";

            ap.selectXPath(xpQ);    
            if (ap.evalXPathToBoolean()) {
                ap.evalXPath();
            }
            else {
                System.out.println(this.getClass()+".getAllElements evalXPathToBoolean["+ap.evalXPathToBoolean()+"]");
            }
        }
        catch(XPathParseException | XPathEvalException | NavException e) {
            e.printStackTrace();
        }            

    }

    private void loadAttributeMap(VTDNav nav, Map<String, String>amap) {      

        nav.push();

        try {
            AutoPilot apAtt = new AutoPilot(nav);
            apAtt.selectXPath("@*");

            int j=-1;
            while ((j=apAtt.evalXPath())!=-1) {
                String name = nav.toString(j);
                String val = nav.toString(j+1);

                amap.put(name, val);
            }                     
        }
        catch(XPathParseException | XPathEvalException | NavException e) {
            e.printStackTrace();
        }

        nav.pop();        
    }     

    private void printTag(VTDNav vn, int level) throws NavException {

        String tag = vn.toString(vn.getCurrentIndex());
        System.out.print("Level ["+level+"] Tag ["+tag+"]");

        Map<String, String>amap = new LinkedHashMap<String, String>();

        loadAttributeMap(vn, amap);

        for (String aname: amap.keySet()) {
            String aval = amap.get(aname);

            System.out.print(" @"+aname+"="+aval);
        }
        System.out.print("\n");
    }

    public static void main(String[] args) {

        VTDParserExample vp = new VTDParserExample();

        try {

            vp.loadFile("src/scce/famedoro.xml");                                     
            vp.getElementsByXpath();
            vp.parseAndPrint();

        }
        catch (Exception ex) {
            ex.printStackTrace();
        }
    }
}

Which produces the following output:

loadFile file exists [src/scce/famedoro.xml]
Level [0] Tag [StockReport]
Level [1] Tag [Article] @Code=027783012 @Height=35 @Width=36 @Length=136 @TotalPacks=4 @AvailablePacks=4 @StockReturnPacks=4 @BlockedPacks=0 @NextExpiryDate=2015-01-17
Level [2] Tag [Machine] @Number=1 @TotalPacks=4 @AvailablePacks=4 @StockReturnPacks=4 @BlockedPacks=0 @NextExpiryDate=2015-01-17
Level [1] Tag [Article] @Code=025349109 @Height=36 @Width=37 @Length=129 @TotalPacks=6 @AvailablePacks=6 @StockReturnPacks=6 @BlockedPacks=0 @NextExpiryDate=2015-01-17
Level [2] Tag [Machine] @Number=1 @TotalPacks=6 @AvailablePacks=6 @StockReturnPacks=6 @BlockedPacks=0 @NextExpiryDate=2015-01-17
Level [1] Tag [Article] @Code=039154327 @Height=0 @Width=0 @Length=0 @TotalPacks=0 @AvailablePacks=0 @StockReturnPacks=0 @BlockedPacks=0 @NextExpiryDate=
Level [1] Tag [Article] @Code=932654167 @Height=57 @Width=99 @Length=137 @TotalPacks=27 @AvailablePacks=27 @StockReturnPacks=27 @BlockedPacks=0 @NextExpiryDate=2014-04-17
Level [2] Tag [Machine] @Number=1 @TotalPacks=16 @AvailablePacks=16 @StockReturnPacks=16 @BlockedPacks=0 @NextExpiryDate=2015-01-17
Level [2] Tag [Machine] @Number=2 @TotalPacks=11 @AvailablePacks=11 @StockReturnPacks=11 @BlockedPacks=0 @NextExpiryDate=2014-04-17

Adding example with AutoPilot loop (rather than purely node based as above) doesn't mix these very well

package scce;

import com.ximpleware.AutoPilot;
import com.ximpleware.NavException;
import com.ximpleware.VTDGen;
import com.ximpleware.VTDNav;
import com.ximpleware.XPathEvalException;
import com.ximpleware.XPathParseException;
import java.io.File;
import java.io.IOException;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 *
 * @author David
 */
public class VTDParserExample {

    VTDGen vg;
    VTDNav vn;
    AutoPilot ap;

    public VTDParserExample() {
        vg = new VTDGen();    
    }

    public void parseAndPrint() throws NavException {

        int level = 0;

        for(boolean el = (vn != null); 
                    el == true ;
                    el = vn.toElement(VTDNav.NEXT_SIBLING)) {

            printTag(vn, level);

            parseAndPrintChildren(level);                
        }

    } 

     private void parseAndPrintChildren(int level) throws NavException {

        vn.push();

        for(boolean el = vn.toElement(VTDNav.FIRST_CHILD); 
                    el == true ;
                    el = vn.toElement(VTDNav.NEXT_SIBLING)) {

            printTag(vn, level + 1);

            parseAndPrintChildren(level + 1);                
        }

        vn.pop();

    }

    private VTDNav loadFile(String filePath) throws IOException {

        File fDoc = new File(filePath);

        if (fDoc != null && fDoc.exists()) {
            System.out.println("loadFile file exists ["+filePath+"]");

            vg.clear();
            if (vg.parseFile(filePath, true)) {
                vn = vg.getNav();
            }
        }
        else {
            throw new IOException("File ["+filePath+"] invalid");
        }             

        if (vn == null) {                
            throw new IOException("Cannot parse file ["+filePath+"]");
        }

        return vn;
    }

    public boolean getElementsByXpath() {
        boolean found = false;

        ap = new AutoPilot(vn);

        try
        {
            String xpQ = "//Machine";

            ap.selectXPath(xpQ);    
            if (ap.evalXPathToBoolean()) {
                found = true;
            }
            else {
                System.out.println(this.getClass()+".getAllElements evalXPathToBoolean["+ap.evalXPathToBoolean()+"]");
            }
        }
        catch(XPathParseException e) {
            e.printStackTrace();
        }            

        return found;
    }

    private void loadAttributeMap(VTDNav nav, Map<String, String>amap) {      

        nav.push();

        try {
            AutoPilot apAtt = new AutoPilot(nav);
            apAtt.selectXPath("@*");

            int j=-1;
            while ((j=apAtt.evalXPath())!=-1) {
                String name = nav.toString(j);
                String val = nav.toString(j+1);

                amap.put(name, val);
            }                     
        }
        catch(XPathParseException | XPathEvalException | NavException e) {
            e.printStackTrace();
        }

        nav.pop();        
    }     

    private void printTag(VTDNav vn, int level) throws NavException {

        String tag = vn.toString(vn.getCurrentIndex());
        System.out.print("Level ["+level+"] Tag ["+tag+"]");

        Map<String, String>amap = new LinkedHashMap<String, String>();

        loadAttributeMap(vn, amap);

        for (String aname: amap.keySet()) {
            String aval = amap.get(aname);

            System.out.print(" @"+aname+"="+aval);
        }
        System.out.print("\n");
    }

    public static void main(String[] args) {

        VTDParserExample vp = new VTDParserExample();

        try {

            vp.loadFile("src/scce/famedoro.xml");
            if (vp.getElementsByXpath()) {
                 vp.parseAndPrintAP();                
            }
        }
        catch (Exception ex) {
            ex.printStackTrace();
        }
    }

    private void parseAndPrintAP() {
        int level = 0;
        int result = -1;

        try {
            while((result = ap.evalXPath())!=-1){
                printTag(vn, level);

                parseAndPrintChildren(level);                

            }
        } catch (XPathEvalException | NavException ex) {
            ex.printStackTrace();
        }
    }

}

This - with different XPath set to "//Machine" produces:

loadFile file exists [src/scce/famedoro.xml]
Level [0] Tag [Machine] @Number=1 @TotalPacks=4 @AvailablePacks=4 @StockReturnPacks=4 @BlockedPacks=0 @NextExpiryDate=2015-01-17
Level [0] Tag [Machine] @Number=1 @TotalPacks=6 @AvailablePacks=6 @StockReturnPacks=6 @BlockedPacks=0 @NextExpiryDate=2015-01-17
Level [0] Tag [Machine] @Number=1 @TotalPacks=16 @AvailablePacks=16 @StockReturnPacks=16 @BlockedPacks=0 @NextExpiryDate=2015-01-17
Level [0] Tag [Machine] @Number=2 @TotalPacks=11 @AvailablePacks=11 @StockReturnPacks=11 @BlockedPacks=0 @NextExpiryDate=2014-04-17