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The Java Print Service API (JPS API).

The Java^TM Print Service API (JPS API).

Background

This API was begun as part of the efforts of the JINI^TM printing working group (JPWG) including Xerox Corp. The JPWG wished to ensure that printing though the JINI printing API would unify as well as possible with existing Java print APIs as they developed. Consequently the JSR 006 Unified Printing API was proposed to unify Java programming language printing APIs which may otherwise unnecessarily diverge.

Specific goals of the API are

To be usable on small footprint platforms (eg Java 2 Micro Edition profiles), which may not include any UI packages.
To integrate with the existing Java 2 Printing API, and JINI printing
To use the job submission model of the Internet Printing Protocol (IPP) 1.1 and the attribute names of IPP 1.1 as much as possible.

The package may be delivered in two ways:

As a standalone package which can be used with Java 2 based platforms to provide access to print services
As an integrated part of a future version of the Java 2 SE platform

Approach

The draft API specification is very largely derived from work performed by the JINI Printing Working Group (JPWG) which asked the JSR006 expert group to take elements of the API they had developed and promote it to become a standard part of the Java 2 platform through the Java Community Process. As such these APIs have already benefited from almost a year of development and review by elements of the JINI community, notably including many of the most prominent printer vendors, (including, but not limited to, Xerox, Lexmark, Canon, Epson, Kodak, HP).

The JINI community work can be viewed by becoming a member of the JINI community at http://www.jini.org.

In essence the classes in the JINI API which have broad applicability to printing applications, have been identified.

Where possible the classes and interfaces have been unchanged from the JINI ones.

In other cases non-JINI specific versions have been created which largely mirror the JINI-specific classes.

This draft specification will be updated to reflect both JCP feedback and final API refinements in the JINI Printing API 1.0 draft.

The key elements of the Java Print Service API are:

Target users of the API

Any applications which want to be able to print through Java printing APIs.

This API will allow client applications to provide rich access to the capablities of print services available such as printer browsing and selection, and discovery of the capablities of those printers, selection of printers for a printer job, specification of a printer job such as paper sizes, etc. Availability of specific capabalities is necessarily dependent on the underlying print service.

Since all capabilities will be exposed though API server applications become first class citizens of this API.

Server applications may be beneficiaries of the capabilities for spooling documents to print services, whereas previously only graphics calls could be used to generate printer jobs from Java applications.

API Overview>

Print Service Providers

The abstract class PrintServiceLookup may be implemented by any party which installs it using the SPI JAR file specification.

This class provides a standardised API for looking up instances of print services. For example an IPP print service provider, a JINI lookup service, or a JNDI-based directory service may each be implementations of this class which can return PrintServices. An API is provided to locate print services which can print a particular type of document in combination with a specified set of job attributes (see below).

IPP Attributes

The definition of the attributes defined by the IPP constitutes the majority of the JPS API. These cover concepts such as resolution, copies, media sizes, job priority, and page ranges.

Document Types

A DocFlavor class which encapsulates a MIME type and a document representation class is used to provide type information for a printable document ("Doc"). A Doc maybe a Postscript file, a JPEG image. a URL or plain text. These are just examples. To print the document call the print() method on a DocPrintJob obtained from a suitable PrintService.

Using the API

A typical use of the API may be to find printers which can support printing 5 copies of a Postscript document, double-sided on A4 paper. stapled.

This involves locating a PrintService which supports all of these requirements, creating a print job, and calling print. This example API usage could look like :-

Doc psDoc = new PrintDoc("file.ps"); // PrintDoc is not part of the API
DocFlavor psFlavor = psDoc.getDocFlavor():
AttributeSet aset = new MyAttributeSet(); // implementation of AttributeSet
aset.add(new Copies(5));
aset.add(MediaSize.A4);
aset.add(Sides.DUPLEX);
aset.add( FinishingsBinding STAPLE);
PrintService[] services = PrintServiceLookup.lookupPrintServices(psFlavor, aset);
if (services != null && services.length > 0) {
   DocPrintJob job  = services[0].createPrintJob();
   try {
        job.print(psDoc, aset);
   }
} catch (PrintException pe) {
}

Limitations of the API

What is exposed at the javax.print API layer is limited to what has been identified as common across printing services. For example this means that in the case of JINI if a particular application needs to set its own policies for dealing with a spontaneous service location and recovery from transient network problems, it probably ought to be a JINI printing client using that API directly rather than the JPS API.

The Java 2D^TM printing API (java.awt.print package) will be unified with the javax.print API to allow clients of that API access to printer capabilities and print job specification. Unifying that API with the Java Print Service API is part of the JSR006 expert group aims, but the specific API to to that is solely part of the core Java 2 platform, and the API to accomplish that is not in the JPS API, but will be included for review in the J2SE releases

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The JavaTM Print Service API (JPS API).