/*
* Copyright 2004 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package javax.xml.bind.annotation.adapters;
/**
* Adapts a Java type for custom marshaling.
*
* <p> <b> Usage: </b> </p>
*
* <p>
* Some Java types do not map naturally to a XML representation, for
* example <tt>HashMap</tt> or other non JavaBean classes. Conversely,
* a XML repsentation may map to a Java type but an application may
* choose to accesss the XML representation using another Java
* type. For example, the schema to Java binding rules bind
* xs:DateTime by default to XmlGregorianCalendar. But an application
* may desire to bind xs:DateTime to a custom type,
* MyXmlGregorianCalendar, for example. In both cases, there is a
* mismatch between <i> bound type </i>, used by an application to
* access XML content and the <i> value type</i>, that is mapped to an
* XML representation.
*
* <p>
* This abstract class defines methods for adapting a bound type to a value
* type or vice versa. The methods are invoked by the JAXB binding
* framework during marshaling and unmarshalling:
*
* <ul>
* <li> <b> XmlAdapter.marshal(...): </b> During marshalling, JAXB
* binding framework invokes XmlAdapter.marshal(..) to adapt a
* bound type to value type, which is then marshaled to XML
* representation. </li>
*
* <li> <b> XmlAdapter.unmarshal(...): </b> During unmarshalling,
* JAXB binding framework first unmarshals XML representation
* to a value type and then invokes XmlAdapter.unmarshal(..) to
* adapt the value type to a bound type. </li>
* </ul>
*
* Writing an adapter therefore involves the following steps:
*
* <ul>
* <li> Write an adapter that implements this abstract class. </li>
* <li> Install the adapter using the annotation {@link
* XmlJavaTypeAdapter} </li>
* </ul>
*
* <p><b>Example:</b> Customized mapping of </tt>HashMap</tt></p>
* <p> The following example illustrates the use of
* <tt>@XmlAdapter</tt> and <tt>@XmlJavaTypeAdapter</tt> to
* customize the mapping of a <tt>HashMap</tt>.
*
* <p> <b> Step 1: </b> Determine the desired XML representation for HashMap.
*
* <pre>
* <hashmap>
* <entry key="id123">this is a value</entry>
* <entry key="id312">this is another value</entry>
* ...
* </hashmap>
* </pre>
*
* <p> <b> Step 2: </b> Determine the schema definition that the
* desired XML representation shown above should follow.
*
* <pre>
*
* <xs:complexType name="myHashMapType">
* <xs:sequence>
* <xs:element name="entry" type="myHashMapEntryType"
* minOccurs = "0" maxOccurs="unbounded"/>
* </xs:sequence>
* </xs:complexType>
*
* <xs:complexType name="myHashMapEntryType">
* <xs:simpleContent>
* <xs:extension base="xs:string">
* <xs:attribute name="key" type="xs:int"/>
* </xs:extension>
* </xs:simpleContent>
* </xs:complexType>
*
* </pre>
*
* <p> <b> Step 3: </b> Write value types that can generate the above
* schema definition.
*
* <pre>
* public class MyHashMapType {
* List<MyHashMapEntryType> entry;
* }
*
* public class MyHashMapEntryType {
* @XmlAttribute
* public Integer key;
*
* @XmlValue
* public String value;
* }
* </pre>
*
* <p> <b> Step 4: </b> Write the adapter that adapts the value type,
* MyHashMapType to a bound type, HashMap, used by the application.
*
* <pre>
* public final class MyHashMapAdapter extends
* XmlAdapter<MyHashMapType,HashMap> { ... }
*
* </pre>
*
* <p> <b> Step 5: </b> Use the adapter.
*
* <pre>
* public class Foo {
* @XmlJavaTypeAdapter(MyHashMapAdapter.class)
* HashMap hashmap;
* ...
* }
* </pre>
*
* The above code fragment will map to the following schema:
*
* <pre>
* <xs:complexType name="Foo">
* <xs:sequence>
* <xs:element name="hashmap" type="myHashMapType"
* </xs:sequence>
* </xs:complexType>
* </pre>
*
* @param <BoundType>
* The type that JAXB doesn't know how to handle. An adapter is written
* to allow this type to be used as an in-memory representation through
* the <tt>ValueType</tt>.
* @param <ValueType>
* The type that JAXB knows how to handle out of the box.
*
* @author <ul><li>Sekhar Vajjhala, Sun Microsystems Inc.</li> <li> Kohsuke Kawaguchi, Sun Microsystems Inc.</li></ul>
* @see XmlJavaTypeAdapter
* @since JAXB 2.0
*/
public abstract class XmlAdapter<ValueType,BoundType> {
/**
* Do-nothing constructor for the derived classes.
*/
protected XmlAdapter() {}
/**
* Convert a value type to a bound type.
*
* @param v
* The value to be converted. Can be null.
* @throws Exception
* if there's an error during the conversion. The caller is responsible for
* reporting the error to the user through {@link javax.xml.bind.ValidationEventHandler}.
*/
public abstract BoundType unmarshal(ValueType v) throws Exception;
/**
* Convert a bound type to a value type.
*
* @param v
* The value to be convereted. Can be null.
* @throws Exception
* if there's an error during the conversion. The caller is responsible for
* reporting the error to the user through {@link javax.xml.bind.ValidationEventHandler}.
*/
public abstract ValueType marshal(BoundType v) throws Exception;
}
|