Class XmlAdapter<ValueType,BoundType>
- Type Parameters:
ValueType
- The type that Jakarta XML Binding knows how to handle out of the box.BoundType
- The type that Jakarta XML Binding doesn't know how to handle. An adapter is written to allow this type to be used as an in-memory representation through theValueType
.
- Direct Known Subclasses:
CollapsedStringAdapter
,HexBinaryAdapter
,NormalizedStringAdapter
Usage:
Some Java types do not map naturally to an XML representation, for
example HashMap
or other non JavaBean classes. Conversely,
an XML representation may map to a Java type but an application may
choose to access 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 Jakarta XML Binding binding framework during marshaling and unmarshalling:
- XmlAdapter.marshal(...): During marshalling, Jakarta XML Binding binding framework invokes XmlAdapter.marshal(..) to adapt a bound type to value type, which is then marshaled to XML representation.
- XmlAdapter.unmarshal(...): During unmarshalling, Jakarta XML Binding binding framework first unmarshalls XML representation to a value type and then invokes XmlAdapter.unmarshal(..) to adapt the value type to a bound type.
- Write an adapter that implements this abstract class.
- Install the adapter using the annotation
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;
...
}
<xs:complexType name="Foo">
<xs:sequence>
<xs:element name="hashmap" type="myHashMapType">
</xs:sequence>
</xs:complexType>
- Author:
- Sekhar Vajjhala, Sun Microsystems Inc.
- Kohsuke Kawaguchi, Sun Microsystems Inc.
- See Also:
-
Constructor Summary
ModifierConstructorDescriptionprotected
Do-nothing constructor for the derived classes. -
Method Summary
-
Constructor Details
-
XmlAdapter
protected XmlAdapter()Do-nothing constructor for the derived classes.
-
-
Method Details
-
unmarshal
Convert a value type to a bound type.- Parameters:
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 throughValidationEventHandler
.
-
marshal
Convert a bound type to a value type.- Parameters:
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 throughValidationEventHandler
.
-