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Java™ Platform Standard Ed. 6 |
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java.lang.Objectjavax.xml.bind.annotation.adapters.XmlAdapter<ValueType,BoundType>
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 ValueType.ValueType - The type that JAXB knows how to handle out of the box.public abstract class XmlAdapter<ValueType,BoundType>
Adapts a Java type for custom marshaling.
Usage:
Some Java types do not map naturally to a XML representation, for example HashMap 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 bound type , used by an application to access XML content and the value type, that is mapped to an XML representation.
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:
XmlJavaTypeAdapter Example: Customized mapping of HashMap
The following example illustrates the use of @XmlAdapter and @XmlJavaTypeAdapter to customize the mapping of a HashMap.
Step 1: Determine the desired XML representation for HashMap.
<hashmap>
<entry key="id123">this is a value</entry>
<entry key="id312">this is another value</entry>
...
</hashmap>
Step 2: Determine the schema definition that the desired XML representation shown above should follow.
<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>
Step 3: Write value types that can generate the above schema definition.
public class MyHashMapType {
List<MyHashMapEntryType> entry;
}
public class MyHashMapEntryType {
@XmlAttribute
public Integer key;
@XmlValue
public String value;
}
Step 4: Write the adapter that adapts the value type, MyHashMapType to a bound type, HashMap, used by the application.
public final class MyHashMapAdapter extends
XmlAdapter<MyHashMapType,HashMap> { ... }
Step 5: Use the adapter.
public class Foo {
@XmlJavaTypeAdapter(MyHashMapAdapter.class)
HashMap hashmap;
...
}
The above code fragment will map to the following schema:
<xs:complexType name="Foo">
<xs:sequence>
<xs:element name="hashmap" type="myHashMapType"
</xs:sequence>
</xs:complexType>
XmlJavaTypeAdapter| Constructor Summary | |
|---|---|
protected |
XmlAdapter()
Do-nothing constructor for the derived classes. |
| Method Summary | |
|---|---|
abstract ValueType |
marshal(BoundType v)
Convert a bound type to a value type. |
abstract BoundType |
unmarshal(ValueType v)
Convert a value type to a bound type. |
| Methods inherited from class java.lang.Object |
|---|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
| Constructor Detail |
|---|
protected XmlAdapter()
| Method Detail |
|---|
public abstract BoundType unmarshal(ValueType v)
throws Exception
v - The value to be converted. Can be null.
Exception - if there's an error during the conversion. The caller is responsible for
reporting the error to the user through ValidationEventHandler.
public abstract ValueType marshal(BoundType v)
throws Exception
v - The value to be convereted. Can be null.
Exception - if there's an error during the conversion. The caller is responsible for
reporting the error to the user through ValidationEventHandler.
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Java™ Platform Standard Ed. 6 |
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