Validating XML Against a XSD Schema

  • Thread starter Thread starter Shailendra Batham
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Shailendra Batham

hi guys
I need your suggestions / opinion for doing this the right way.

I have a XML and a Schema for the same

What I want is when its validated against the schema, it should give custom errors saying what happened and where......

is it possible to do that ?

for eg. if the Attribute is missing or invalid in the following element <Watch ID="999d999">
then it should say ID attribute invalid for "Watch" Element.

Right now the validation works but the error returning our very vague, I need a way where I can customize the error or at least let the user know where the error is at what element and which attribute.

thanks,
Shailendra Batham
 
What language do you use? Below is the sample code in C++:

Validating an XML Document Against an XML Schema Using C++
To validate an XML document file with an XML Schema definition language (XSD) schema file using C++, you load XML and XSD documents and create a schema cache as in the following example.

#include "stdio.h"

#import <msxml4.dll>
using namespace MSXML2;

int checkParseError(IXMLDOMParseErrorPtr pError);
void dump_com_error(_com_error &e);


int main(int argc, char* argv[])
{

CoInitialize(NULL);
try{

IXMLDOMParseErrorPtr pError;

// load the XML file
// ****** you need to use IXMLDOMDocument2 interface *********
IXMLDOMDocument2Ptr pXMLDoc;
HRESULT hr = pXMLDoc.CreateInstance(__uuidof(DOMDocument40));
pXMLDoc->async = VARIANT_FALSE;

hr = pXMLDoc->load("books.xml");

//check on the parser error
if(hr!=VARIANT_TRUE)
{
return checkParseError(pXMLDoc->parseError);
}

//load the XSD file
IXMLDOMDocumentPtr pXSDDoc;
hr = pXSDDoc.CreateInstance(__uuidof(DOMDocument40));
pXSDDoc->async = VARIANT_FALSE;

hr = pXSDDoc->load("books.xsd");

//check on the parser error
if(hr!=VARIANT_TRUE)
{
return checkParseError(pXSDDoc->parseError);
}

//create schemacache
IXMLDOMSchemaCollectionPtr pSchemaCache;
hr = pSchemaCache.CreateInstance(__uuidof(XMLSchemaCache40));
pXMLDoc->schemas = pSchemaCache.GetInterfacePtr();

//hook it up with XML Document
hr = pSchemaCache->add("urn:books", pXSDDoc.GetInterfacePtr());

//call validate
pError = pXMLDoc->validate();

if(pError->errorCode != S_OK)
{
_bstr_t parseError = _bstr_t("Error code: ")+ _bstr_t(pError->errorCode) +_bstr_t("\n") + _bstr_t("Reason: ")+ pError->Getreason();
MessageBox(NULL, (char*)parseError, "Parse Error",MB_OK);
return -1;
}
else
MessageBox(NULL,"Valiation succeeded", "Results",MB_OK);

}
catch(_com_error &e)
{
dump_com_error(e);
}
return 0;
}


int checkParseError(IXMLDOMParseErrorPtr pError)
{
_bstr_t parseError =_bstr_t("At line ")+ _bstr_t(pError->Getline()) + _bstr_t("\n")+ _bstr_t(pError->Getreason());
MessageBox(NULL,parseError, "Parse Error",MB_OK);
return -1;

}

void dump_com_error(_com_error &e)
{
printf("Error\n");
printf("\a\tCode = %08lx\n", e.Error());
printf("\a\tCode meaning = %s", e.ErrorMessage());
_bstr_t bstrSource(e.Source());
_bstr_t bstrDescription(e.Description());
printf("\a\tSource = %s\n", (LPCSTR) bstrSource);
printf("\a\tDescription = %s\n", (LPCSTR) bstrDescription);
}Input file: books.xml

<?xml version="1.0"?>
<x:catalog xmlns:x="urn:books">
<book id="bk101">
<author>Gambardella, Matthew</author>
<title>XML Developer's Guide</title>
<genre>Computer</genre>
<price>44.95</price>
<publish_date>2000-10-01</publish_date>
<description>An in-depth look at creating applications with XML.</description>
</book>
</x:catalog>
Input file: books.xsd

<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema" targetNamespace="urn:books" xmlns:b="urn:books">

<xsd:element name="catalog" type="b:CatalogData"/>
<xsd:complexType name="CatalogData">
<xsd:sequence>
<xsd:element name="book" type="b:bookdata" minOccurs="0" maxOccurs="unbounded"/>
</xsd:sequence>
</xsd:complexType>

<xsd:complexType name="bookdata">
<xsd:sequence>
<xsd:element name="author" type="xsd:string"/>
<xsd:element name="title" type="xsd:string"/>
<xsd:element name="genre" type="xsd:string"/>
<xsd:element name="price" type="xsd:float"/>
<xsd:element name="publish_date" type="xsd:date"/>
<xsd:element name="description" type="xsd:string"/>
</xsd:sequence>
<xsd:attribute name="id" type="xsd:string"/>
</xsd:complexType>
hi guys
I need your suggestions / opinion for doing this the right way.

I have a XML and a Schema for the same

What I want is when its validated against the schema, it should give custom errors saying what happened and where......

is it possible to do that ?

for eg. if the Attribute is missing or invalid in the following element <Watch ID="999d999">
then it should say ID attribute invalid for "Watch" Element.

Right now the validation works but the error returning our very vague, I need a way where I can customize the error or at least let the user know where the error is at what element and which attribute.

thanks,
Shailendra Batham
 
Hi Shailendra,

If you are coding in .Net,

Look at these:

System.Xml.Schema

ValidationEventHandler
ValidationEventArgs

XmlTextReader xmlreader = new XmlTextReader("test.xml");
XmlValidatingReader valid = new XmlValidatingReader(xmlreader);
valid.ValidationType = ValidationType.Schema;

Cheers.
 
Thanks for the reply guys.

hey chua I am using C# and I am using the ValidationEventHandler, it works
fine but this is what error it returns

"The 'ID' attribute has an invalid value according to its data type. An
error occurred at , (2, 9)." string

can we do custom errors like what node's attribute had an error.
 
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