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EclipseLink/UserGuide/MOXy/Runtime/Converting XML to Objects/Validating Against an XML Schema
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Contents
Validating against an XML Schema
If you would like to validate your objects against an XML Schema during marshalling and unmarshalling, you can make use of JAXB's ValidationEventHandler.
Example
In this example we would like to validate our objects against the following XML schema:
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"> <xs:element name="customer"> <xs:complexType> <xs:sequence> <xs:element name="name" type="stringMaxSize5"/> <xs:element ref="phone-number" maxOccurs="2"/> </xs:sequence> </xs:complexType> </xs:element> <xs:element name="phone-number"> <xs:complexType> <xs:sequence/> </xs:complexType> </xs:element> <xs:simpleType name="stringMaxSize5"> <xs:restriction base="xs:string"> <xs:maxLength value="5"/> </xs:restriction> </xs:simpleType> </xs:schema>
Notice the following constraints:
- The customer's name cannot be longer than 5 characters.
- The customer cannot have more than 2 phone numbers.
The Customer class is shown below. Notice that the class does not contain any validation code.
package example; import java.util.ArrayList; import java.util.List; import javax.xml.bind.annotation.XmlElement; import javax.xml.bind.annotation.XmlRootElement; @XmlRootElement public class Customer { private String name; private List<PhoneNumber> phoneNumbers = new ArrayList<PhoneNumber>(); public String getName() { return name; } public void setName(String name) { this.name = name; } @XmlElement(name="phone-number") public List<PhoneNumber> getPhoneNumbers() { return phoneNumbers; } public void setPhoneNumbers(List<PhoneNumber> phoneNumbers) { this.phoneNumbers = phoneNumbers; } }
ValidationEventHandler
You can recieve JAXB validation events by providing your own subclass of ValidationEventHandler. The event is represented as an instance of ValidationEvent, and provides many details about the issue. The data is similar to what is available from a SAXParseException.
Returning false from the handleEvent method will cause the JAXB operation to stop.
Returning true will allow the method to continue, if possible.
In this example, we will simply print out an event's data when one is recieved:
package example; import javax.xml.bind.ValidationEvent; import javax.xml.bind.ValidationEventHandler; public class MyValidationEventHandler implements ValidationEventHandler { public boolean handleEvent(ValidationEvent event) { System.out.println("\nEVENT"); System.out.println("SEVERITY: " + event.getSeverity()); System.out.println("MESSAGE: " + event.getMessage()); System.out.println("LINKED EXCEPTION: " + event.getLinkedException()); System.out.println("LOCATOR"); System.out.println(" LINE NUMBER: " + event.getLocator().getLineNumber()); System.out.println(" COLUMN NUMBER: " + event.getLocator().getColumnNumber()); System.out.println(" OFFSET: " + event.getLocator().getOffset()); System.out.println(" OBJECT: " + event.getLocator().getObject()); System.out.println(" NODE: " + event.getLocator().getNode()); System.out.println(" URL: " + event.getLocator().getURL()); return true; } }
Enabling Validation
In addition to providing an implementation of ValidationEventHandler, an instance of Schema must be set on the Marshaller or Unmarshaller.
package example; import java.io.File; import javax.xml.XMLConstants; import javax.xml.bind.JAXBContext; import javax.xml.bind.Unmarshaller; import javax.xml.validation.Schema; import javax.xml.validation.SchemaFactory; public class UnmarshalDemo { public static void main(String[] args) throws Exception { SchemaFactory sf = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI); Schema schema = sf.newSchema(new File("customer.xsd")); JAXBContext jc = JAXBContext.newInstance(Customer.class); Unmarshaller unmarshaller = jc.createUnmarshaller(); unmarshaller.setSchema(schema); unmarshaller.setEventHandler(new MyValidationEventHandler()); Customer customer = (Customer) unmarshaller.unmarshal(new File("input.xml")); } }
Input (input.xml)
<customer> <name>Jane Doe</name> <phone-number/> <phone-number/> <phone-number/> </customer>
Output
The validation performed during the unmarshal raised three events. The first two events are related to the text value of the "name" element being too long. The third event is related to the extra "phone-number" element.
EVENT SEVERITY: 1 MESSAGE: cvc-maxLength-valid: Value 'Jane Doe' with length = '8' is not facet-valid with respect to maxLength '5' for type 'stringWithMaxSize5'. LINKED EXCEPTION: org.xml.sax.SAXParseException: cvc-maxLength-valid: Value 'Jane Doe' with length = '8' is not facet-valid with respect to maxLength '5' for type 'stringWithMaxSize5'. LOCATOR LINE NUMBER: 3 COLUMN NUMBER: 25 OFFSET: -1 OBJECT: null NODE: null URL: null EVENT SEVERITY: 1 MESSAGE: cvc-type.3.1.3: The value 'Jane Doe' of element 'name' is not valid. LINKED EXCEPTION: org.xml.sax.SAXParseException: cvc-type.3.1.3: The value 'Jane Doe' of element 'name' is not valid. LOCATOR LINE NUMBER: 3 COLUMN NUMBER: 25 OFFSET: -1 OBJECT: null NODE: null URL: null EVENT SEVERITY: 1 MESSAGE: cvc-complex-type.2.4.d: Invalid content was found starting with element 'customer'. No child element '{phone-number}' is expected at this point. LINKED EXCEPTION: org.xml.sax.SAXParseException: cvc-complex-type.2.4.d: Invalid content was found starting with element 'customer'. No child element '{phone-number}' is expected at this point. LOCATOR LINE NUMBER: 7 COLUMN NUMBER: 12 OFFSET: -1 OBJECT: null NODE: null URL: null
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