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/* * Copyright 2006 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */ package javax.xml.bind.annotation.adapters; import javax.xml.bind.Unmarshaller; import javax.xml.bind.Marshaller; /** * 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<HashMap, MyHashMapType> { ... } * * </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; }