Automatic XSD validation

Question

According to the lxml documentation \"The DTD is retrieved automatically based on the DOCTYPE of the parsed document. All you have to do is use a parser that has DTD validat

Answer 1

I have a project that has over 100 different schemas and xml trees. In order to manage all of them and validate them i did a few things.

1) I created a file (i.e. xmlTrees.py) where i created a dictionary of every xml and corresponding schema associated with it, and the xml path. This allowed me to have a single place to get both xml & the schema used to validate that xml.

MY_XML = {'url':'/pathToTree/myTree.xml', 'schema':'myXSD.xsd'}

2) In the project we have equally as many namespaces (very hard to manage). So what i did was again i created a single file that contained all the namespaces in the format lxml likes. Then in my tests and scripts i would just always pass the superset of namespaces.

ALL_NAMESPACES = {
    'namespace1':  'http://www.example.org',
    'namespace2':  'http://www.example2.org'
}

3) For basic/generic validation i ended up creating a basic function i could call:

    def validateXML(content, schemaContent):

    try:
        xmlSchema_doc = etree.parse(schemaContent);
        xmlSchema = etree.XMLSchema(xmlSchema_doc);
        xml = etree.parse(StringIO(content));
    except:
        logging.critical("Could not parse schema or content to validate xml");
        response['valid'] = False;
        response['errorlog'] = "Could not parse schema or content to validate xml";

    response = {}
    # Validate the content against the schema.
    try:
        xmlSchema.assertValid(xml)
        response['valid'] = True
        response['errorlog'] = None
    except etree.DocumentInvalid, info:
        response['valid'] = False
        response['errorlog'] = xmlSchema.error_log

    return response

basically any function that wants to use this needs to send the xml content and the xsd content as strings. This provided me with the most flexability. I then just placed this function in a file where i had all my xml helper functions.

Answer 2

You could extract the schemas yourself and import them into a root schema:

from lxml import etree

XSI = "http://www.w3.org/2001/XMLSchema-instance"
XS = '{http://www.w3.org/2001/XMLSchema}'


SCHEMA_TEMPLATE = """<?xml version = "1.0" encoding = "UTF-8"?>
<xs:schema xmlns="http://dummy.libxml2.validator"
targetNamespace="http://dummy.libxml2.validator"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
version="1.0"
elementFormDefault="qualified"
attributeFormDefault="unqualified">
</xs:schema>"""


def validate_XML(xml):
    """Validate an XML file represented as string. Follow all schemaLocations.

    :param xml: XML represented as string.
    :type xml: str
    """
    tree = etree.XML(xml)
    schema_tree = etree.XML(SCHEMA_TEMPLATE)
    # Find all unique instances of 'xsi:schemaLocation="<namespace> <path-to-schema.xsd> ..."'
    schema_locations = set(tree.xpath("//*/@xsi:schemaLocation", namespaces={'xsi': XSI}))
    for schema_location in schema_locations:
        # Split namespaces and schema locations ; use strip to remove leading
        # and trailing whitespace.
        namespaces_locations = schema_location.strip().split()
        # Import all found namspace/schema location pairs
        for namespace, location in zip(*[iter(namespaces_locations)] * 2):
            xs_import = etree.Element(XS + "import")
            xs_import.attrib['namespace'] = namespace
            xs_import.attrib['schemaLocation'] = location
            schema_tree.append(xs_import)
    # Contstruct the schema
    schema = etree.XMLSchema(schema_tree)
    # Validate!
    schema.assertValid(tree)

BTW, your simpletest.xsd is missing the targetNamespace.

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.example.org" elementFormDefault="qualified">
    <xs:element name="name" type="xs:string"/>
</xs:schema>

With the code above, your example document validates against this schema.