Package jakarta.xml.bind.annotation.adapters

Class XmlAdapter<ValueType,​BoundType>

  • Type Parameters:
    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 the ValueType.
    ValueType - The type that Jakarta XML Binding knows how to handle out of the box.
    Direct Known Subclasses:
    CollapsedStringAdapter, HexBinaryAdapter, NormalizedStringAdapter
    public abstract class XmlAdapter<ValueType,​BoundType>
extends java.lang.Object
    Adapts a Java type for custom marshaling.

    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.
    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.

    Step 2: Determine the schema definition that the desired XML representation shown above should follow.

    Step 3: Write value types that can generate the above schema definition. {@snippet : public class MyHashMapType { List<MyHashMapEntryType> entry; } public class MyHashMapEntryType {

    Since:
    1.6, JAXB 2.0
    Author:
    • Sekhar Vajjhala, Sun Microsystems Inc.
    • Kohsuke Kawaguchi, Sun Microsystems Inc.
    See Also:
    XmlJavaTypeAdapter

    • Constructor Summary

      Constructors 
      Modifier Constructor Description
      protected XmlAdapter()
      Do-nothing constructor for the derived classes.

    • Constructor Detail

      • XmlAdapter

        protected XmlAdapter()
        Do-nothing constructor for the derived classes.

    • Method Detail

      • unmarshal

        public abstract BoundType unmarshal​(ValueType v)
                             throws java.lang.Exception
        Convert a value type to a bound type.
        Parameters:
        v - The value to be converted. Can be null.
        Throws:
        java.lang.Exception - 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 java.lang.Exception
        Convert a bound type to a value type.
        Parameters:
        v - The value to be converted. Can be null.
        Throws:
        java.lang.Exception - if there's an error during the conversion. The caller is responsible for reporting the error to the user through ValidationEventHandler.