Unmarshaller JDK 1.6)

Description

public interface Unmarshaller

The Unmarshaller class governs the process of deserializing XML data into newly created Java content trees, optionally validating the XML data as it is unmarshalled.

The Unmarshaller class governs the process of deserializing XML data into newly created Java content trees, optionally validating the XML data as it is unmarshalled. It provides an overloading of unmarshal methods for many different input kinds.

Unmarshalling from a File:

       JAXBContext jc = JAXBContext.newInstance( "com.acme.foo" );
       Unmarshaller u = jc.createUnmarshaller();
       Object o = u.unmarshal( new File( "nosferatu.xml" ) );

Unmarshalling from an InputStream:

       InputStream is = new FileInputStream( "nosferatu.xml" );
       JAXBContext jc = JAXBContext.newInstance( "com.acme.foo" );
       Unmarshaller u = jc.createUnmarshaller();
       Object o = u.unmarshal( is );

Unmarshalling from a URL:

       JAXBContext jc = JAXBContext.newInstance( "com.acme.foo" );
       Unmarshaller u = jc.createUnmarshaller();
       URL url = new URL( "http://beaker.east/nosferatu.xml" );
       Object o = u.unmarshal( url );

Unmarshalling from a StringBuffer using a javax.xml.transform.stream.StreamSource:

       JAXBContext jc = JAXBContext.newInstance( "com.acme.foo" );
       Unmarshaller u = jc.createUnmarshaller();
       StringBuffer xmlStr = new StringBuffer( "<?xml version="1.0"?>..." );
       Object o = u.unmarshal( new StreamSource( new StringReader( xmlStr.toString() ) ) );

Unmarshalling from a org.w3c.dom.Node:

       JAXBContext jc = JAXBContext.newInstance( "com.acme.foo" );
       Unmarshaller u = jc.createUnmarshaller();
 
       DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
       dbf.setNamespaceAware(true);
       DocumentBuilder db = dbf.newDocumentBuilder();
       Document doc = db.parse(new File( "nosferatu.xml"));

       Object o = u.unmarshal( doc );

Unmarshalling from a javax.xml.transform.sax.SAXSource using a client specified validating SAX2.0 parser:

       // configure a validating SAX2.0 parser (Xerces2)
       static final String JAXP_SCHEMA_LANGUAGE =
           "http://java.sun.com/xml/jaxp/properties/schemaLanguage";
       static final String JAXP_SCHEMA_LOCATION =
           "http://java.sun.com/xml/jaxp/properties/schemaSource";
       static final String W3C_XML_SCHEMA =
           "http://www.w3.org/2001/XMLSchema";

       System.setProperty( "javax.xml.parsers.SAXParserFactory",
                           "org.apache.xerces.jaxp.SAXParserFactoryImpl" );

       SAXParserFactory spf = SAXParserFactory.newInstance();
       spf.setNamespaceAware(true);
       spf.setValidating(true);
       SAXParser saxParser = spf.newSAXParser();
       
       try {
           saxParser.setProperty(JAXP_SCHEMA_LANGUAGE, W3C_XML_SCHEMA);
           saxParser.setProperty(JAXP_SCHEMA_LOCATION, "http://....");
       } catch (SAXNotRecognizedException x) {
           // exception handling omitted
       }

       XMLReader xmlReader = saxParser.getXMLReader();
       SAXSource source = 
           new SAXSource( xmlReader, new InputSource( "http://..." ) );

       // Setup JAXB to unmarshal
       JAXBContext jc = JAXBContext.newInstance( "com.acme.foo" );
       Unmarshaller u = jc.createUnmarshaller();
       ValidationEventCollector vec = new ValidationEventCollector();
       u.setEventHandler( vec );
       
       // turn off the JAXB provider's default validation mechanism to 
       // avoid duplicate validation
       u.setValidating( false )

       // unmarshal
       Object o = u.unmarshal( source );

       // check for events
       if( vec.hasEvents() ) {
          // iterate over events
       }

Unmarshalling from a StAX XMLStreamReader:

       JAXBContext jc = JAXBContext.newInstance( "com.acme.foo" );
       Unmarshaller u = jc.createUnmarshaller();
 
       javax.xml.stream.XMLStreamReader xmlStreamReader = 
           javax.xml.stream.XMLInputFactory().newInstance().createXMLStreamReader( ... );
 
       Object o = u.unmarshal( xmlStreamReader );

Unmarshalling from a StAX XMLEventReader:

       JAXBContext jc = JAXBContext.newInstance( "com.acme.foo" );
       Unmarshaller u = jc.createUnmarshaller();
 
       javax.xml.stream.XMLEventReader xmlEventReader = 
           javax.xml.stream.XMLInputFactory().newInstance().createXMLEventReader( ... );
 
       Object o = u.unmarshal( xmlEventReader );

Unmarshalling XML Data

Unmarshalling can deserialize XML data that represents either an entire XML document or a subtree of an XML document. Typically, it is sufficient to use the unmarshalling methods described by Unmarshal root element that is declared globally. These unmarshal methods utilize JAXBContext's mapping of global XML element declarations and type definitions to JAXB mapped classes to initiate the unmarshalling of the root element of XML data. When the JAXBContext's mappings are not sufficient to unmarshal the root element of XML data, the application can assist the unmarshalling process by using the unmarshal by declaredType methods. These methods are useful for unmarshalling XML data where the root element corresponds to a local element declaration in the schema.

An unmarshal method never returns null. If the unmarshal process is unable to unmarshal the root of XML content to a JAXB mapped object, a fatal error is reported that terminates processing by throwing JAXBException.

Unmarshal a root element that is globally declared

The unmarshal methods that do not have an declaredType parameter use JAXBContext to unmarshal the root element of an XML data. The JAXBContext instance is the one that was used to create this Unmarshaller. The JAXBContext instance maintains a mapping of globally declared XML element and type definition names to JAXB mapped classes. The unmarshal method checks if JAXBContext has a mapping from the root element's XML name and/or @xsi:type to a JAXB mapped class. If it does, it umarshalls the XML data using the appropriate JAXB mapped class. Note that when the root element name is unknown and the root element has an @xsi:type, the XML data is unmarshalled using that JAXB mapped class as the value of a JAXBElement. When the JAXBContext object does not have a mapping for the root element's name nor its @xsi:type, if it exists, then the unmarshal operation will abort immediately by throwing a UnmarshalException. This exception scenario can be worked around by using the unmarshal by declaredType methods described in the next subsection.

Unmarshal by Declared Type

The unmarshal methods with a declaredType parameter enable an application to deserialize a root element of XML data, even when there is no mapping in JAXBContext of the root element's XML name. The unmarshaller unmarshals the root element using the application provided mapping specified as the declaredType parameter. Note that even when the root element's element name is mapped by JAXBContext, the declaredType parameter overrides that mapping for deserializing the root element when using these unmarshal methods. Additionally, when the root element of XML data has an xsi:type attribute and that attribute's value references a type definition that is mapped to a JAXB mapped class by JAXBContext, that the root element's xsi:type attribute takes precedence over the unmarshal methods declaredType parameter. These methods always return a JAXBElement<declaredType> instance. The table below shows how the properties of the returned JAXBElement instance are set.

Unmarshal By Declared Type returned JAXBElement

JAXBElement Property Value

name xml element name

value instanceof declaredType

declaredType unmarshal method declaredType parameter

scope null (actual scope is unknown)

Unmarshal By Declared Type returned JAXBElement
value	`instanceof declaredType`
declaredType	unmarshal method `declaredType` parameter
scope	`null` (actual scope is unknown)

The following is an example of unmarshal by declaredType method.

Unmarshal by declaredType from a org.w3c.dom.Node:

       Schema fragment for example
       <xs:schema>
          <xs:complexType name="FooType">...<\xs:complexType>
          <!-- global element declaration "PurchaseOrder" -->
          <xs:element name="PurchaseOrder">
              <xs:complexType>
                 <xs:sequence>
                    <!-- local element declaration "foo" -->
                    <xs:element name="foo" type="FooType"/>
                    ...
                 </xs:sequence>
              </xs:complexType>
          </xs:element>
       </xs:schema>

       JAXBContext jc = JAXBContext.newInstance( "com.acme.foo" );
       Unmarshaller u = jc.createUnmarshaller();
 
       DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
       dbf.setNamespaceAware(true);
       DocumentBuilder db = dbf.newDocumentBuilder();
       Document doc = db.parse(new File( "nosferatu.xml"));
       Element  fooSubtree = ...; // traverse DOM till reach xml element foo, constrained by a 
                                  // local element declaration in schema.
 
       // FooType is the JAXB mapping of the type of local element declaration foo.
       JAXBElement<FooType> foo = u.unmarshal( fooSubtree, FooType.class);

Support for SAX2.0 Compliant Parsers

A client application has the ability to select the SAX2.0 compliant parser of their choice. If a SAX parser is not selected, then the JAXB Provider's default parser will be used. Even though the JAXB Provider's default parser is not required to be SAX2.0 compliant, all providers are required to allow a client application to specify their own SAX2.0 parser. Some providers may require the client application to specify the SAX2.0 parser at schema compile time. See unmarshal(Source) for more detail.

Validation and Well-Formedness

A client application can enable or disable JAXP 1.3 validation mechanism via the setSchema(javax.xml.validation.Schema) API. Sophisticated clients can specify their own validating SAX 2.0 compliant parser and bypass the JAXP 1.3 validation mechanism using the unmarshal(Source) API.
Since unmarshalling invalid XML content is defined in JAXB 2.0, the Unmarshaller default validation event handler was made more lenient than in JAXB 1.0. When schema-derived code generated by JAXB 1.0 binding compiler is registered with JAXBContext, the default unmarshal validation handler is DefaultValidationEventHandler and it terminates the marshal operation after encountering either a fatal error or an error. For a JAXB 2.0 client application, there is no explicitly defined default validation handler and the default event handling only terminates the marshal operation after encountering a fatal error.

Supported Properties

There currently are not any properties required to be supported by all JAXB Providers on Unmarshaller. However, some providers may support their own set of provider specific properties.

Unmarshal Event Callbacks

The Unmarshaller provides two styles of callback mechanisms that allow application specific processing during key points in the unmarshalling process. In 'class defined' event callbacks, application specific code placed in JAXB mapped classes is triggered during unmarshalling. 'External listeners' allow for centralized processing of unmarshal events in one callback method rather than by type event callbacks.
'Class defined' event callback methods allow any JAXB mapped class to specify its own specific callback methods by defining methods with the following method signature:
   // This method is called immediately after the object is created and before the unmarshalling of this 
   // object begins. The callback provides an opportunity to initialize JavaBean properties prior to unmarshalling.
   void beforeUnmarshal(Unmarshaller, Object parent);
 
   //This method is called after all the properties (except IDREF) are unmarshalled for this object, 
   //but before this object is set to the parent object.
   void afterUnmarshal(Unmarshaller, Object parent);
 
The class defined callback methods should be used when the callback method requires access to non-public methods and/or fields of the class.
The external listener callback mechanism enables the registration of a Unmarshaller.Listener instance with an Unmarshaller.setListener(Listener). The external listener receives all callback events, allowing for more centralized processing than per class defined callback methods. The external listener receives events when unmarshalling proces is marshalling to a JAXB element or to JAXB mapped class.
The 'class defined' and external listener event callback methods are independent of each other, both can be called for one event. The invocation ordering when both listener callback methods exist is defined in Unmarshaller.Listener.beforeUnmarshal(Object, Object) and Unmarshaller.Listener.afterUnmarshal(Object, Object).
An event callback method throwing an exception terminates the current unmarshal process.

See also: JAXBContext Marshaller Validator

Methods

Hide/Show inherited methods

public A getAdapter (Class< A> type)

Gets the adapter associated with the specified type.

public AttachmentUnmarshaller getAttachmentUnmarshaller ()

public ValidationEventHandler getEventHandler () throws JAXBException

Return the current event handler or the default event handler if one hasn't been set.

public Listener getListener ()

Return Unmarshaller.Listener registered with this Unmarshaller.

public Object getProperty (String name) throws PropertyException

Get the particular property in the underlying implementation of Unmarshaller.

public Schema getSchema ()

Get the JAXP 1.3 Schema object being used to perform unmarshal-time validation.

public UnmarshallerHandler getUnmarshallerHandler ()

Get an unmarshaller handler object that can be used as a component in an XML pipeline.

public boolean ~~isValidating~~ () throws JAXBException

Indicates whether or not the Unmarshaller is configured to validate during unmarshal operations.

public void setAdapter (Class< A> type, A adapter)

Associates a configured instance of XmlAdapter with this unmarshaller.

public void setAdapter (XmlAdapter adapter)

Associates a configured instance of XmlAdapter with this unmarshaller.

public void setAttachmentUnmarshaller (AttachmentUnmarshaller au)

Associate a context that resolves cid's, content-id URIs, to binary data passed as attachments.

public void setEventHandler (ValidationEventHandler handler) throws JAXBException

Allow an application to register a ValidationEventHandler.

public void setListener (Listener listener)

public void setProperty (String name, Object value) throws PropertyException

Set the particular property in the underlying implementation of Unmarshaller.

public void setSchema (Schema schema)

Specify the JAXP 1.3 Schema object that should be used to validate subsequent unmarshal operations against.

public void ~~setValidating~~ (boolean validating) throws JAXBException

Specifies whether or not the default validation mechanism of the Unmarshaller should validate during unmarshal operations.

public Object unmarshal (File f) throws JAXBException

Unmarshal XML data from the specified file and return the resulting content tree.

public Object unmarshal (InputSource source) throws JAXBException

Unmarshal XML data from the specified SAX InputSource and return the resulting content tree.

public Object unmarshal (InputStream is) throws JAXBException

Unmarshal XML data from the specified InputStream and return the resulting content tree.

public Object unmarshal (Node node) throws JAXBException

Unmarshal global XML data from the specified DOM tree and return the resulting content tree.

public JAXBElement< T> unmarshal (Node node, Class< T> declaredType) throws JAXBException

Unmarshal XML data by JAXB mapped declaredType and return the resulting content tree.

public Object unmarshal (Reader reader) throws JAXBException

Unmarshal XML data from the specified Reader and return the resulting content tree.

public Object unmarshal (Source source) throws JAXBException

Unmarshal XML data from the specified XML Source and return the resulting content tree.

Implements Unmarshal Global Root Element.

SAX 2.0 Parser Pluggability

A client application can choose not to use the default parser mechanism supplied with their JAXB provider. Any SAX 2.0 compliant parser can be substituted for the JAXB provider's default mechanism. To do so, the client application must properly configure a SAXSource containing an XMLReader implemented by the SAX 2.0 parser provider. If the XMLReader has an org.xml.sax.ErrorHandler registered on it, it will be replaced by the JAXB Provider so that validation errors can be reported via the ValidationEventHandler mechanism of JAXB. If the SAXSource does not contain an XMLReader, then the JAXB provider's default parser mechanism will be used.

This parser replacement mechanism can also be used to replace the JAXB provider's unmarshal-time validation engine. The client application must properly configure their SAX 2.0 compliant parser to perform validation (as shown in the example above). Any SAXParserExceptions encountered by the parser during the unmarshal operation will be processed by the JAXB provider and converted into JAXB ValidationEvent objects which will be reported back to the client via the ValidationEventHandler registered with the Unmarshaller. Note: specifying a substitute validating SAX 2.0 parser for unmarshalling does not necessarily replace the validation engine used by the JAXB provider for performing on-demand validation.

The only way for a client application to specify an alternate parser mechanism to be used during unmarshal is via the unmarshal(SAXSource) API. All other forms of the unmarshal method (File, URL, Node, etc) will use the JAXB provider's default parser and validator mechanisms.
Returns: the newly created root object of the java content tree
Parameters:
- source - the XML Source to unmarshal XML data from (providers are only required to support SAXSource, DOMSource, and StreamSource)
Throws:
- JAXBException - If any unexpected errors occur while unmarshalling
- UnmarshalException - If the {@link ValidationEventHandler ValidationEventHandler} returns false from its handleEvent method or the Unmarshaller is unable to perform the XML to Java binding. See Unmarshalling XML Data
- IllegalArgumentException - If the Source parameter is null
See Also: Unmarshaller.unmarshal(javax.xml.transform.Source, Class),

public JAXBElement< T> unmarshal (Source source, Class< T> declaredType) throws JAXBException

Unmarshal XML data from the specified XML Source by declaredType and return the resulting content tree.

public Object unmarshal (URL url) throws JAXBException

Unmarshal XML data from the specified URL and return the resulting content tree.

public Object unmarshal (XMLEventReader reader) throws JAXBException

Unmarshal XML data from the specified pull parser and return the resulting content tree.

public JAXBElement< T> unmarshal (XMLEventReader reader, Class< T> declaredType) throws JAXBException

Unmarshal root element to JAXB mapped declaredType and return the resulting content tree.

public Object unmarshal (XMLStreamReader reader) throws JAXBException

Unmarshal XML data from the specified pull parser and return the resulting content tree.

public JAXBElement< T> unmarshal (XMLStreamReader reader, Class< T> declaredType) throws JAXBException

Unmarshal root element to JAXB mapped declaredType and return the resulting content tree.

Unmarshal By Declared Type returned JAXBElement
JAXBElement Property	Value
name	`xml element name`
value	`instanceof declaredType`
declaredType	unmarshal method `declaredType` parameter
scope	`null` (actual scope is unknown)