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*
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* accompanied this code).
*
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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()
* <CODE>getDoc()</CODE>} 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()
* <CODE>next()</CODE>} 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() <CODE>getDoc()</CODE>} 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()
* <CODE>next()</CODE>} 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 ocurred 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;
}