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package javax.xml.bind.annotation;

import javax.xml.bind.ValidationEventHandler;

import javax.xml.transform.Result;

import javax.xml.transform.Source;

/**

 * Converts an element (and its descendants)

 * from/to DOM (or similar) representation.

 *

 * <p>

 * Implementations of this interface will be used in conjunction with

 * {@link XmlAnyElement} annotation to map an element of XML into a representation

 * of infoset such as W3C DOM.

 *

 * <p>

 * Implementations hide how a portion of XML is converted into/from such

 * DOM-like representation, allowing JAXB providers to work with arbitrary

 * such library.

 *

 * <P>

 * This interface is intended to be implemented by library writers

 * and consumed by JAXB providers. None of those methods are intended to

 * be called from applications.

 *

 * @author Kohsuke Kawaguchi

 * @since JAXB2.0

 */

public interface DomHandler<ElementT,ResultT extends Result> {

    /**

     * When a JAXB provider needs to unmarshal a part of a document into an

     * infoset representation, it first calls this method to create a

     * {@link Result} object.

     *

     * <p>

     * A JAXB provider will then send a portion of the XML

     * into the given result. Such a portion always form a subtree

     * of the whole XML document rooted at an element.

     *

     * @param errorHandler

     *      if any error happens between the invocation of this method

     *      and the invocation of {@link #getElement(Result)}, they

     *      must be reported to this handler.

     *

     *      The caller must provide a non-null error handler.

     *

     *      The {@link Result} object created from this method

     *      may hold a reference to this error handler.

     *

     * @return

     *      null if the operation fails. The error must have been reported

     *      to the error handler.

     */

    ResultT createUnmarshaller( ValidationEventHandler errorHandler );

    /**

     * Once the portion is sent to the {@link Result}. This method is called

     * by a JAXB provider to obtain the unmarshalled element representation.

     *

     * <p>

     * Multiple invocations of this method may return different objects.

     * This method can be invoked only when the whole sub-tree are fed

     * to the {@link Result} object.

     *

     * @param rt

     *      The {@link Result} object created by {@link #createUnmarshaller(ValidationEventHandler)}.

     *

     * @return

     *      null if the operation fails. The error must have been reported

     *      to the error handler.

     */

    ElementT getElement(ResultT rt);

    /**

     * This method is called when a JAXB provider needs to marshal an element

     * to XML.

     *

     * <p>

     * If non-null, the returned {@link Source} must contain a whole document

     * rooted at one element, which will then be weaved into a bigger document

     * that the JAXB provider is marshalling.

     *

     * @param errorHandler

     *      Receives any errors happened during the process of converting

     *      an element into a {@link Source}.

     *

     *      The caller must provide a non-null error handler.

     *

     * @return

     *      null if there was an error. The error should have been reported

     *      to the handler.

     */

    Source marshal( ElementT n, ValidationEventHandler errorHandler );

}