javax/print/PrintServiceLookup.java

/* PrintServiceLookup.java --
   Copyright (C) 2004, 2006 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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General Public License for more details.

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02110-1301 USA.

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making a combined work based on this library.  Thus, the terms and
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permission to link this library with independent modules to produce an
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package javax.print;

import gnu.classpath.ServiceFactory;
import gnu.javax.print.CupsPrintServiceLookup;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Iterator;

import javax.print.attribute.AttributeSet;


/**
 * <code>PrintServiceLookup</code> implementations provide a way to lookup
 * print services based on different constraints.
 * <p>
 * Implementations are located and loaded automatically through the SPI JAR
 * file specification. Therefore implementation classes must provide a default
 * constructor for instantiation. Furthermore, applications are able to
 * register further instances directly at runtime.
 * </p><p>
 * If an SecurityManager is installed implementors should call
 * <code>checkPrintJobAccess()</code> to disable access for untrusted code.
 * This check is to be made in every lookup service implementation for
 * flexibility. Print services registered by applications through
 * <code>registerService(PrintService)</code> are suppressed in the
 * lookup results if a security manager is installed and disallows access.
 * </p>
 *
 * @author Michael Koch (konqueror@gmx.de)
 * @author Wolfgang Baer (WBaer@gmx.de)
 */
public abstract class PrintServiceLookup
{

  private static final CupsPrintServiceLookup systemProvider;
  private static final HashSet printServices;
  private static final HashSet printServiceLookups;

  static
  {
    systemProvider = new CupsPrintServiceLookup();

    printServices = new HashSet();
    printServiceLookups = new HashSet();

    // check for service providers
    Iterator it = ServiceFactory.lookupProviders(PrintServiceLookup.class);

    while (it.hasNext())
      printServiceLookups.add(it.next());
  }

  /**
   * Constructs a <code>PrintServiceLookup</code> object.
   */
  public PrintServiceLookup()
  {
    // nothing to do here
  }

  /**
   * Explicitly registers the provided print service lookup implementation.
   * <p>
   * The registration will silently fail (returning <code>false</code>) if
   * the lookup service is already registered or the registration somehow
   * else fails.
   * </p>
   *
   * @param sp the print service lookup implementation to register.
   * @return <code>true</code> if registered, <code>false</code> otherwise.
   */
  public static boolean registerServiceProvider(PrintServiceLookup sp)
  {
    return printServiceLookups.add(sp);
  }

  /**
   * Explicitly registers the provided print service instance.
   * <p>
   * The registration will silently fail (returning <code>false</code>) if
   * the print service instance is already registered or the registration
   * somehow else fails.
   * </p>
   * @param service the single print service to register.
   * @return <code>true</code> if registered, <code>false</code> otherwise.
   */
  public static boolean registerService(PrintService service)
  {
    if (service instanceof StreamPrintService)
      return false;

    // security
    try
      {
        SecurityManager sm = System.getSecurityManager();
        if (sm != null)
          sm.checkPrintJobAccess();

        return printServices.add(service);
      }
    catch (SecurityException se)
      {
        return false;
      }
  }

  /**
   * Searches print services capable of printing in the given document flavor
   * which supports the specified printing attributes.
   *
   * @param flavor the document flavor to support. If <code>null</code> this
   * constraint is ignored during lookup.
   * @param attributes the printing attributes to support. If
   * <code>null</code> this constraint is ignored during lookup.
   * @return The resulting available print services, or an array of length 0
   * if none is found.
   */
  public static final PrintService[] lookupPrintServices(DocFlavor flavor,
    AttributeSet attributes)
  {
    ArrayList result = new ArrayList();

    PrintService[] services =
      systemProvider.getPrintServices(flavor, attributes);
    result.addAll(Arrays.asList(services));

    for (Iterator it = printServiceLookups.iterator(); it.hasNext(); )
      {
        PrintServiceLookup lookup = (PrintServiceLookup) it.next();
        services = lookup.getPrintServices(flavor, attributes);
        result.addAll(Arrays.asList(services));
      }

    for (Iterator it = printServices.iterator(); it.hasNext(); )
      {
        PrintService service = (PrintService) it.next();
        if (systemProvider.checkPrintService(flavor, attributes, service))
          result.add(service);
      }

    return (PrintService[]) result.toArray(new PrintService[result.size()]);
  }

  /**
   * Searches print services capable of multi document printing in all of the
   * given document flavors and supporting the specified printing attributes.
   *
   * @param flavors the document flavors to support. If <code>null</code> this
   * constraint is ignored during lookup.
   * @param attributes the printing attributes to support. If
   * <code>null</code> this constraint is ignored during lookup.
   * @return The resulting available multi document print services, or an
   * array of length 0 if none is found.
   */
  public static final MultiDocPrintService[] lookupMultiDocPrintServices(
    DocFlavor[] flavors, AttributeSet attributes)
  {
    ArrayList result = new ArrayList();

    MultiDocPrintService[] services =
      systemProvider.getMultiDocPrintServices(flavors, attributes);
    result.addAll(Arrays.asList(services));

    for (Iterator it = printServiceLookups.iterator(); it.hasNext(); )
      {
        PrintServiceLookup lookup = (PrintServiceLookup) it.next();
        services = lookup.getMultiDocPrintServices(flavors, attributes);
        result.addAll(Arrays.asList(services));
      }

    for (Iterator it = printServices.iterator(); it.hasNext(); )
      {
        PrintService service = (PrintService) it.next();
        if (systemProvider.checkMultiDocPrintService(flavors, attributes, service))
          result.add(service);
      }

    return (MultiDocPrintService[]) result.toArray(
      new MultiDocPrintService[result.size()]);
  }


  /**
   * Searches the default print service in the current environment.
   * <p>
   * If multiple lookup services are registered and each has a default
   * print service the result is not specified. Usually the default
   * print service of the native platform lookup service is returned.
   * </p><p>
   * The GNU classpath implementation will return the CUPS default
   * printing service as the default print service, if available.
   * </p><p>
   * The default print service may be overriden by users through
   * the property <code>javax.print.defaultPrinter</code>. A service
   * specified must be found to be returned as the default.
   * </p>
   *
   * @return The default print service, or <code>null</code> if none found.
   */
  public static final PrintService lookupDefaultPrintService()
  {
    // TODO Find out what the property controls and use it
    // String defaultPrinter = System.getProperty("javax.print.defaultPrinter");

    // first test for platform specified default services
    PrintService service = systemProvider.getDefaultPrintService();

    if (service != null)
      return service;

    // none available by systemDefaultProvider
    // search in other registered ones and take first
    for (Iterator it = printServiceLookups.iterator(); it.hasNext(); )
      {
        service = ((PrintServiceLookup) it.next()).getDefaultPrintService();
        if (service != null)
          return service;
      }

    return null;
  }

  /**
   * Not to be called directly by applications.
   *
   * @return The default lookup service of the implementing lookup service or
   * <code>null</code> if there is no default one.
   */
  public abstract PrintService getDefaultPrintService();

  /**
   * Not to be called directly by applications.
   *
   * @param flavors the document flavors which have to be supported.
   * @param attributes the attributes which have to be supported.
   *
   * @return The multidoc print services of the implementing lookup service
   * for the given parameters, or an array of length 0 if none is available.
   */
  public abstract MultiDocPrintService[]
    getMultiDocPrintServices(DocFlavor[] flavors, AttributeSet attributes);

  /**
   * Not to be called directly by applications.
   *
   * @return All known print services of the implementing lookup service
   * regardless of supported features, or an array of length 0 if none is
   * available.
   */
  public abstract PrintService[] getPrintServices();

  /**
   * Not to be called directly by applications.
   *
   * @param flavor the document flavor which has to be supported.
   * @param attributes the attributes which have to be supported.
   *
   * @return The print services of the implementing lookup service
   * for the given parameters, or an array of length 0 if none is available.
   */
  public abstract PrintService[]
    getPrintServices(DocFlavor flavor, AttributeSet attributes);
}