XmlAdapter (Java Platform SE 6) (original) (raw)

javax.xml.bind.annotation.adapters

Class XmlAdapter<ValueType,BoundType>

java.lang.Object javax.xml.bind.annotation.adapters.XmlAdapter<ValueType,BoundType>

Type Parameters:

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.

Direct Known Subclasses:

CollapsedStringAdapter, HexBinaryAdapter, NormalizedStringAdapter

public abstract class XmlAdapter<ValueType,BoundType>

extends Object

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:

• XmlAdapter.marshal(...): During marshalling, JAXB binding framework invokes XmlAdapter.marshal(..) to adapt a bound type to value type, which is then marshaled to XML representation.
• XmlAdapter.unmarshal(...): 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. Writing an adapter therefore involves the following steps:
• 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;
     ...
 }

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>

Since:

JAXB 2.0

See Also:

XmlJavaTypeAdapter

XmlAdapter

protected XmlAdapter()

Do-nothing constructor for the derived classes.

unmarshal

public abstract BoundType unmarshal(ValueType v) throws Exception

Convert a value type to a bound type.

Parameters:

v - The value to be converted. Can be null.

Throws:

[Exception](../../../../../java/lang/Exception.html "class in java.lang") - if there's an error during the conversion. The caller is responsible for reporting the error to the user through ValidationEventHandler.

marshal

public abstract ValueType marshal(BoundType v) throws Exception

Convert a bound type to a value type.

Parameters:

v - The value to be convereted. Can be null.

Throws:

[Exception](../../../../../java/lang/Exception.html "class in java.lang") - if there's an error during the conversion. The caller is responsible for reporting the error to the user through ValidationEventHandler.

Submit a bug or feature
For further API reference and developer documentation, see Java SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.

Copyright © 1993, 2015, Oracle and/or its affiliates. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.

Scripting on this page tracks web page traffic, but does not change the content in any way.