XMLスキーマ検証（XSD）— 実践ガイド

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">

  <!-- Root element -->
  <xs:element name="catalog">
    <xs:complexType>
      <xs:sequence>
        <!-- One or more product elements -->
        <xs:element name="product" type="ProductType" minOccurs="1" maxOccurs="unbounded"/>
      </xs:sequence>
      <xs:attribute name="version" type="xs:string" use="required"/>
    </xs:complexType>
  </xs:element>

  <!-- Product complex type -->
  <xs:complexType name="ProductType">
    <xs:sequence>
      <xs:element name="name" type="xs:string"/>
      <xs:element name="description" type="xs:string" minOccurs="0"/>
      <xs:element name="price" type="PriceType"/>
      <xs:element name="stock" type="xs:nonNegativeInteger"/>
      <xs:element name="categories" type="CategoriesType"/>
    </xs:sequence>
    <xs:attribute name="id" type="ProductIdType" use="required"/>
    <xs:attribute name="status" type="ProductStatusType" use="optional" default="active"/>
  </xs:complexType>

  <!-- Price with currency attribute -->
  <xs:complexType name="PriceType">
    <xs:simpleContent>
      <xs:extension base="xs:decimal">
        <xs:attribute name="currency" type="CurrencyCodeType" use="required"/>
      </xs:extension>
    </xs:simpleContent>
  </xs:complexType>

  <!-- Categories — zero or more category strings -->
  <xs:complexType name="CategoriesType">
    <xs:sequence>
      <xs:element name="category" type="xs:string" minOccurs="0" maxOccurs="unbounded"/>
    </xs:sequence>
  </xs:complexType>

  <!-- Product ID: alphanumeric, starts with P, 4-10 chars -->
  <xs:simpleType name="ProductIdType">
    <xs:restriction base="xs:string">
      <xs:pattern value="P[A-Z0-9]{3,9}"/>
    </xs:restriction>
  </xs:simpleType>

  <!-- Allowed product statuses -->
  <xs:simpleType name="ProductStatusType">
    <xs:restriction base="xs:string">
      <xs:enumeration value="active"/>
      <xs:enumeration value="discontinued"/>
      <xs:enumeration value="out_of_stock"/>
    </xs:restriction>
  </xs:simpleType>

  <!-- ISO 4217 currency codes — a subset -->
  <xs:simpleType name="CurrencyCodeType">
    <xs:restriction base="xs:string">
      <xs:enumeration value="USD"/>
      <xs:enumeration value="EUR"/>
      <xs:enumeration value="GBP"/>
      <xs:enumeration value="JPY"/>
    </xs:restriction>
  </xs:simpleType>

</xs:schema>

pip install lxml

from lxml import etree

# Load the schema
with open('catalog.xsd', 'rb') as f:
    schema_doc = etree.parse(f)
schema = etree.XMLSchema(schema_doc)

# Valid XML
valid_xml = """<?xml version="1.0"?>
<catalog version="1.0">
  <product id="P0012" status="active">
    <name>Mechanical Keyboard</name>
    <price currency="USD">189.00</price>
    <stock>42</stock>
    <categories>
      <category>Electronics</category>
      <category>Peripherals</category>
    </categories>
  </product>
</catalog>"""

xml_doc = etree.fromstring(valid_xml.encode())
if schema.validate(xml_doc):
    print("Valid!")
else:
    for error in schema.error_log:
        print(f"Error at line {error.line}: {error.message}")

# Invalid XML — missing required 'stock', bad product ID format
invalid_xml = """<?xml version="1.0"?>
<catalog version="1.0">
  <product id="BADID">
    <name>Test Product</name>
    <price currency="USD">10.00</price>
    <categories/>
  </product>
</catalog>"""

invalid_doc = etree.fromstring(invalid_xml.encode())
schema.validate(invalid_doc)
for error in schema.error_log:
    print(f"Line {error.line}: {error.message}")
# Line 3: Element 'product', attribute 'id': 'BADID' is not a valid value of the atomic type 'ProductIdType'.
# Line 7: Element 'categories': Missing child element(s). Expected is ( category ).  ← if minOccurs > 0

import javax.xml.XMLConstants;
import javax.xml.validation.Schema;
import javax.xml.validation.SchemaFactory;
import javax.xml.validation.Validator;
import javax.xml.transform.stream.StreamSource;
import java.io.File;
import org.xml.sax.SAXException;
import java.io.IOException;

SchemaFactory factory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
Schema schema = factory.newSchema(new File("catalog.xsd"));
Validator validator = schema.newValidator();

try {
    validator.validate(new StreamSource(new File("catalog.xml")));
    System.out.println("Valid!");
} catch (SAXException e) {
    System.out.println("Validation error: " + e.getMessage());
} catch (IOException e) {
    System.out.println("IO error: " + e.getMessage());
}