Validering av XML

Hvem er hvem | Validering | Enkelt valideringseksempel

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Validering av XML mot Schema

Vi bruker fila med olympiske sprint resultater som utgangspunkt og bygger en applikasjon som skal demonstrere to ting:

bruk av løpernavn som enkel nøkkel for å lokalisere løperens deltagelse i flere olympiader.
validering av XML-fil mot Schema-fil

Råmaterialet er beskevet i modulen Noen datasett, og har denne strukturen


<?xml version="1.0" encoding="ISO-8859-1"?>
<IOC>
  <OlympicGame place="Barcelona" year="1992">
    <event dist="100m">
      <athlet>
        <name>Dennis Mitchell</name>
        <nation>USA</nation>
        <result>10.04</result>
      </athlet>
      ...
    </event>
    ...
  </OlympicGame>
  ...
</IOC>

I sin helhet: all_results.xml

Hvem er hvem

Vi ønsker å lage en liste av deltagere (athlets) der hver deltager er representert kun en gang. Vi baserer oss da på at navnet er god nok identifikasjon. Koden for å etablere lista og finne en deltagers deltagelse blir slik:

// adding name of athlets to listbox
private void buttonAthlets_Click(object sender, EventArgs e)
{
    if (m_Doc == null) { return; }
    XmlNodeList alist = m_Doc.SelectNodes("//name");
    foreach (XmlElement aelt in alist)
    {
        String nText = aelt.InnerText;
        // already there ?
        if (listBoxSelection.Items.IndexOf(nText) == -1)
            listBoxSelection.Items.Add(nText);
    }
}

// selecting an athletname, report all performances
private void listBoxSelection_SelectedIndexChanged(object sender, EventArgs e)
{
    String t = listBoxSelection.SelectedItem.ToString();
    String xpath = String.Format("//athlet[name='{0}']", t);
    XmlNodeList same = m_Doc.SelectNodes(xpath);
    textBox1.Text = "";
    foreach (XmlElement a in same)
    {
        textBox1.Text += String.Format("{0} i {1} - {2}\r\n",
                     ((XmlElement)a.ParentNode).GetAttribute("dist"),
                     ((XmlElement)a.ParentNode.ParentNode).GetAttribute("place"),
                     ((XmlElement)a.ParentNode.ParentNode).GetAttribute("year"));
    }
}

Validering

Vi ønsker å validere fila med resultater. Vi kan gjøre dette på mange måter. Her bruker vi en enkel framgangsmåte:

last opp XML-fila i Visual Studio
fra menyen XML, velg Create Schema
lage denne i prosjektkatalogen
adder schema-fila til prosjektet
sørg for at både xml-fila og schema-fila kopieres til den katalogen applikasjonen kjøres

String XSDFILEPATH = 
	Path.Combine(Application.StartupPath, "all_results.xsd");
String XMLFILEPATH = 
	Path.Combine(Application.StartupPath, "all_results.xml");

Følgende kode etablerer XmlDocumentet, viser det i en webbrowser kontrol og validerer.

private void postInitialize()
{
    try
    {
        String filename=Path.Combine(Application.StartupPath,
                             "all_results.xml");
        webBrowser1.Url = new Uri(XMLFILEPATH);
        m_Doc = new XmlDocument();
        
        // will fail if malformed or not found
        m_Doc.Load(XMLFILEPATH);
        m_Doc.Normalize();
        
        // validate
        XmlReaderSettings settings = new XmlReaderSettings();
        settings.Schemas.Add(null, XSDFILEPATH);
        settings.ValidationType = ValidationType.Schema;
        settings.ValidationEventHandler += 
            new ValidationEventHandler(SchemaValidationEventHandler);
        XmlReader rdr = 
            XmlReader.Create(new StringReader(m_Doc.InnerXml), settings);
        while (rdr.Read()) { }
     }
    catch (Exception ex)
    {
        webBrowser1.DocumentText = 
            String.Format(@"<html><body>
                          <p>Sorry:</p>
                          <p>{0}</p>
                          </body></html>", ex.Message);
        m_Doc = null;
    }
}

Merk metoden SchemaValidationEventHandler som gor oss advarsler ogfeilmeldinger under valideringen.

// pick up validation errors/warnngs
// report in text box
private void SchemaValidationEventHandler(object sender, ValidationEventArgs e)
{
    switch (e.Severity)
    {
        case XmlSeverityType.Error:
            textBox1.Text += String.Format("\r\nError: {0}", e.Message);
            break;
        case XmlSeverityType.Warning:
            textBox1.Text += String.Format("\r\nWarning: {0}", e.Message);
            break;
    }
}

Vi har valgt et enkelt demonstarsjonseksempel, laget schema-fila ukritisk og brukt den uten endringer. I de fleste tilfelle ønsker vi å validere filer som er laget eller importert fra programmer vi ikke har kontroll over. En fornuftig framgangsmåter er trolig å lage en schema-fil basert på et eksempel og deretter editere denne for hånd for å generalisere og eller presisere. Den schema-fila vi får laget i dette eksempelet ser slik ut:

<?xml version="1.0" encoding="iso-8859-1"?>
<xs:schema attributeFormDefault="unqualified" 
           elementFormDefault="qualified" 
           xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xs:element name="IOC">
    <xs:complexType>
      <xs:sequence>
        <xs:element maxOccurs="unbounded" name="OlympicGame">
          <xs:complexType>
            <xs:sequence>
              <xs:element maxOccurs="unbounded" name="event">
                <xs:complexType>
                  <xs:sequence>
                    <xs:element maxOccurs="unbounded" name="athlet">
                      <xs:complexType>
                        <xs:sequence>
                          <xs:element name="name" type="xs:string" />
                          <xs:element name="nation" type="xs:string" />
                          <xs:element name="result" type="xs:decimal" />
                        </xs:sequence>
                      </xs:complexType>
                    </xs:element>
                  </xs:sequence>
                  <xs:attribute name="dist" type="xs:string" use="required" />
                </xs:complexType>
              </xs:element>
            </xs:sequence>
            <xs:attribute name="place" type="xs:string" use="required" />
            <xs:attribute name="year" type="xs:unsignedShort" use="required" />
          </xs:complexType>
        </xs:element>
      </xs:sequence>
    </xs:complexType>
  </xs:element>
</xs:schema>

For å kunne bearbeide denne må vi sette oss inn hvordan xsd-filer er bygget opp. Vi forfølger ikke dette her, men det er mye å hente både i presisering av lovlige verdirer og i generalisering av hvordan validerbare filer kan bygges opp. Er det f.eks. viktig at elementene name, nation,result kommer i nøyaktig den rekkefølgen ? En modifisert versjon kan se slik ut:

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema attributeFormDefault="unqualified"
           elementFormDefault="qualified"
           xmlns:xs="http://www.w3.org/2001/XMLSchema">
    <xs:simpleType name="AT_3">
        <xs:restriction base="xs:string">
            <xs:enumeration value="100m"/>
            <xs:enumeration value="200m"/>
            <xs:enumeration value="400m"/>
        </xs:restriction>
    </xs:simpleType>
    <xs:simpleType name="AT_2">
        <xs:restriction base="xs:short">
            <xs:enumeration value="1992"/>
            <xs:enumeration value="1996"/>
            <xs:enumeration value="2000"/>
            <xs:enumeration value="2004"/>
            <xs:enumeration value="2008"/>
        </xs:restriction>
    </xs:simpleType>
    <xs:simpleType name="AT_1">
        <xs:restriction base="xs:string">
            <xs:enumeration value="Athens"/>
            <xs:enumeration value="Atlanta"/>
            <xs:enumeration value="Barcelona"/>
            <xs:enumeration value="Beijing"/>
            <xs:enumeration value="Sidney"/>
        </xs:restriction>
    </xs:simpleType>
    <xs:attribute name="year" type="AT_2"/>
    <xs:attribute name="dist" type="AT_3"/>
    <xs:attribute name="place" type="AT_1"/>
    <xs:element name="result" type="xs:decimal"/>
    <xs:element name="nation" type="xs:string"/>
    <xs:element name="name" type="xs:string"/>
    <xs:element name="event">
        <xs:complexType>
            <xs:sequence>
                <xs:element ref="athlet" maxOccurs="unbounded"/>
            </xs:sequence>
            <xs:attribute ref="dist" use="required"/>
        </xs:complexType>
    </xs:element>
    <xs:element name="athlet">
        <xs:complexType>
            <xs:sequence>
                <xs:element ref="name"/>
                <xs:element ref="nation"/>
                <xs:element ref="result"/>
            </xs:sequence>
        </xs:complexType>
    </xs:element>
    <xs:element name="OlympicGame">
        <xs:complexType>
            <xs:sequence>
                <xs:element ref="event" maxOccurs="unbounded"/>
            </xs:sequence>
            <xs:attribute ref="year" use="required"/>
            <xs:attribute ref="place" use="required"/>
        </xs:complexType>
    </xs:element>
    <xs:element name="IOC">
        <xs:complexType>
            <xs:sequence>
                <xs:element ref="OlympicGame" maxOccurs="unbounded"/>
            </xs:sequence>
        </xs:complexType>
    </xs:element>
</xs:schema>

Koden i Formen er i sin helhet slik:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Xml;
using System.Xml.Schema;
using System.IO;
using System.Windows.Forms;
namespace allxml2
{
    public partial class Form1 : Form
    {
        XmlDocument m_Doc = null;
        String XSDFILEPATH = 
            Path.Combine(Application.StartupPath, "all_results.xsd");
        //String XSDFILEPATH =
        //    Path.Combine(Application.StartupPath, "modified.xsd");
        String XMLFILEPATH = 
            Path.Combine(Application.StartupPath, "all_results.xml");
        
        public Form1()
        {
            InitializeComponent();
            postInitialize();
        }
        #region setup
        private void postInitialize()
        {
            try
            {
                String filename=Path.Combine(Application.StartupPath,
                                     "all_results.xml");
                webBrowser1.Url = new Uri(XMLFILEPATH);
                m_Doc = new XmlDocument();
                
                // will fail if malformed or not found
                m_Doc.Load(XMLFILEPATH);
                m_Doc.Normalize();
                
                // validate
                XmlReaderSettings settings = new XmlReaderSettings();
                settings.Schemas.Add(null, XSDFILEPATH);
                settings.ValidationType = ValidationType.Schema;
                settings.ValidationEventHandler += 
                    new ValidationEventHandler(SchemaValidationEventHandler);
                XmlReader rdr = 
                    XmlReader.Create(new StringReader(m_Doc.InnerXml), settings);
                while (rdr.Read()) { }
             }
            catch (Exception ex)
            {
                webBrowser1.DocumentText = 
                    String.Format(@"<html><body>
                                  <p>Sorry:</p>
                                  <p>{0}</p>
                                  </body></html>", ex.Message);
                m_Doc = null;
            }
        }
        #endregion setup
        #region errors
        // pick up validation errors/warnngs
        // report in text box
        private void SchemaValidationEventHandler(object sender, ValidationEventArgs e)
        {
            switch (e.Severity)
            {
                case XmlSeverityType.Error:
                    textBox1.Text += String.Format("\r\nError: {0}", e.Message);
                    break;
                case XmlSeverityType.Warning:
                    textBox1.Text += String.Format("\r\nWarning: {0}", e.Message);
                    break;
            }
        }
        #endregion errors

        #region naming
        // adding name of athlets to listbox
        private void buttonAthlets_Click(object sender, EventArgs e)
        {
            if (m_Doc == null) { return; }
            XmlNodeList alist = m_Doc.SelectNodes("//name");
            foreach (XmlElement aelt in alist)
            {
                String nText = aelt.InnerText;
                // already there ?
                if (listBoxSelection.Items.IndexOf(nText) == -1)
                    listBoxSelection.Items.Add(nText);
            }
        }
        
        // selecting an athletname, report all performances
        private void listBoxSelection_SelectedIndexChanged(object sender, EventArgs e)
        {
            String t = listBoxSelection.SelectedItem.ToString();
            String xpath = String.Format("//athlet[name='{0}']", t);
            XmlNodeList same = m_Doc.SelectNodes(xpath);
            textBox1.Text = "";
            foreach (XmlElement a in same)
            {
                textBox1.Text += String.Format("{0} i {1} - {2}\r\n",
                             ((XmlElement)a.ParentNode).GetAttribute("dist"),
                             ((XmlElement)a.ParentNode.ParentNode).GetAttribute("place"),
                             ((XmlElement)a.ParentNode.ParentNode).GetAttribute("year"));
            }
        }
        #endregion naming
    }

}

Enkelt valideringseksempel

Et enkelt eksempel som gjør det lett å eksperimentere med schemaer og validering. Eksempelet er bygget rundt de samme dataene som over, men programmet gjør ikke annet enn å laste en XML-fil og validere den.

screen2

Koden i Formen er i sin helhet slik:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Xml;
using System.Xml.Schema;
using System.IO;
namespace XMLValidate
{
    public partial class Form1 : Form
    {
        XmlDocument doc=null;
        String validationMsg;
        public Form1()
        {
            InitializeComponent();
            prepare();
        }
        
        private void prepare()
        {
            // if you want to validate the original:
            //textBoxURL.Text = "http://www.it.hiof.no/~borres/commondata/olympiade/all_results.xml";
            textBoxURL.Text = Path.Combine(Application.StartupPath, "results.xml");
            // if you want to validate against the original schema:
            //textBoxSchema.Text = "http://www.it.hiof.no/~borres/commondata/olympiade/olymp.xsd";
            textBoxSchema.Text = Path.Combine(Application.StartupPath,"schema.xsd");
        }
        private void buttonLoad_Click(object sender, EventArgs e)
        {
            String source = textBoxURL.Text;
            try
            {
                doc = new XmlDocument();
                doc.Load(source);
                textBoxLoad.Text = "Loaded and parsed as wellformed";
                textBoxValidate.Text = "";
            }
            catch (Exception ex)
            {
                textBoxLoad.Text = ex.Message;
                doc = null;
            }
        }
        private void buttonValidate_Click(object sender, EventArgs e)
        {
            if (doc == null)
            {
                textBoxValidate.Text = "No document Loaded";
                return;
            }
            ValidationEventHandler vh=
                new ValidationEventHandler(HandleValidateEvents);
            try{
                validationMsg = "Validated as OK";
                doc.Schemas.Add(null, textBoxSchema.Text);
                doc.Validate(vh);
                textBoxValidate.Text = validationMsg;
            }
            catch(Exception ex)
            {
                textBoxValidate.Text = ex.Message;
            }
        }
        // a delegate reporting errors
        private void HandleValidateEvents(object ob, ValidationEventArgs args)
        {
            if (validationMsg.EndsWith("OK"))
                validationMsg="";
            switch (args.Severity)
            {
                case XmlSeverityType.Error:
                    validationMsg += String.Format("\r\nError: {0}", args.Message);
                    break;
                case XmlSeverityType.Warning:
                    validationMsg += String.Format("\r\nWarning: {0}", args.Message);
                    break;
            }
            validationMsg += args.Message + "\r\n";
        }
    }
}

Du kan lett bytte ut eller endre innholdet i de to filene: results.xml og schema.xsd, eller du kan ganske enkelt endre adressen i formen.

Referanser

Prosjekt:

https://svn.hiof.no/svn/psource/Csharpspikes/xmlvalidate

Enklet eksempel;

https://svn.hiof.no/svn/psource/Csharpspikes/xmlvalidate2

Vedlikehold

B.Stenseth, revidert januar 2011

(Velkommen) Moduler>XML>Validering (RSS-leser)