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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

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 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

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package javax.print;

import java.io.IOException;

/**

 * Interface MultiDoc specifies the interface for an object that supplies more

 * than one piece of print data for a Print Job. "Doc" is a short,

 * easy-to-pronounce term that means "a piece of print data," and a "multidoc"

 * is a group of several docs. The client passes to the Print Job an object

 * that implements interface MultiDoc, and the Print Job calls methods on

 *  that object to obtain the print data.

 * <P>

 * Interface MultiDoc provides an abstraction similar to a "linked list" of

 * docs. A multidoc object is like a node in the linked list, containing the

 * current doc in the list and a pointer to the next node (multidoc) in the

 * list. The Print Job can call the multidoc's {@link #getDoc()

 * getDoc()} method to get the current doc. When it's ready to go

 * on to the next doc, the Print Job can call the multidoc's {@link #next()

 * next()} method to get the next multidoc, which contains the

 * next doc. So Print Job code for accessing a multidoc might look like this:

 * <PRE>

 *      void processMultiDoc(MultiDoc theMultiDoc) {

 *

 *          MultiDoc current = theMultiDoc;

 *          while (current != null) {

 *              processDoc (current.getDoc());

 *              current = current.next();

 *          }

 *      }

 * </PRE>

 * <P>

 * Of course, interface MultiDoc can be implemented in any way that fulfills

 * the contract; it doesn't have to use a linked list in the implementation.

 * <P>

 * To get all the print data for a multidoc print job, a Print Service

 * proxy could use either of two patterns:

 * <OL TYPE=1>

 * <LI>

 * The <B>interleaved</B> pattern: Get the doc from the current multidoc. Get

 * the print data representation object from the current doc. Get all the print

 * data from the print data representation object. Get the next multidoc from

 * the current multidoc, and repeat until there are no more. (The code example

 * above uses the interleaved pattern.)

 * <P>

 * <LI>

 * The <B>all-at-once</B> pattern: Get the doc from the current multidoc, and

 * save the doc in a list. Get the next multidoc from the current multidoc, and

 * repeat until there are no more. Then iterate over the list of saved docs. Get

 * the print data representation object from the current doc. Get all the print

 * data from the print data representation object. Go to the next doc in the

 * list, and repeat until there are no more.

 * </OL>

 * Now, consider a printing client that is generating print data on the fly and

 * does not have the resources to store more than one piece of print data at a

 * time. If the print service proxy used the all-at-once pattern to get the

 * print data, it would pose a problem for such a client; the client would have

 * to keep all the docs' print data around until the print service proxy comes

 * back and asks for them, which the client is not able to do. To work with such

 * a client, the print service proxy must use the interleaved pattern.

 * <P>

 * To address this problem, and to simplify the design of clients providing

* multiple docs to a Print Job, every Print Service proxy that supports

 * multidoc print jobs is required to access a MultiDoc object using the

 * interleaved pattern. That is, given a MultiDoc object, the print service

 * proxy will call {@link #getDoc() getDoc()} one or more times

 * until it successfully obtains the current Doc object. The print service proxy

 * will then obtain the current doc's print data, not proceeding until all the

 * print data is obtained or an unrecoverable error occurs. If it is able to

 * continue, the print service proxy will then call {@link #next()

 * next()} one or more times until it successfully obtains either

 * the next MultiDoc object or an indication that there are no more. An

 * implementation of interface MultiDoc can assume the print service proxy will

 * follow this interleaved pattern; for any other pattern of usage, the MultiDoc

 * implementation's behavior is unspecified.

 * <P>

 * There is no restriction on the number of client threads that may be

 * simultaneously accessing the same multidoc. Therefore, all implementations of

 * interface MultiDoc must be designed to be multiple thread safe. In fact, a

 * client thread could be adding docs to the end of the (conceptual) list while

 * a Print Job thread is simultaneously obtaining docs from the beginning of the

 * list; provided the multidoc object synchronizes the threads properly, the two

 * threads will not interfere with each other

 */

public interface MultiDoc {

    /**

     * Obtain the current doc object.

     *

     * @return  Current doc object.

     *

     * @exception  IOException

     *     Thrown if a error occurred reading the document.

     */

    public Doc getDoc() throws IOException;

    /**

     * Go to the multidoc object that contains the next doc object in the

     * sequence of doc objects.

     *

     * @return  Multidoc object containing the next doc object, or null if

     * there are no further doc objects.

     *

     * @exception  IOException

     *     Thrown if an error occurred locating the next document

     */

    public MultiDoc next() throws IOException;

}