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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * 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,
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 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 */


package javax.print;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import javax.print.attribute.AttributeSet;

import sun.awt.AppContext;
import java.util.ServiceLoader;
import java.util.ServiceConfigurationError;

Implementations of this class provide lookup services for
print services (typically equivalent to printers) of a particular type.

Multiple implementations may be installed concurrently.
All implementations must be able to describe the located printers
as instances of a PrintService.
Typically implementations of this service class are located
automatically in JAR files (see the SPI JAR file specification).
These classes must be instantiable using a default constructor.
Alternatively applications may explicitly register instances
at runtime.

Applications use only the static methods of this abstract class.
The instance methods are implemented by a service provider in a subclass
and the unification of the results from all installed lookup classes
are reported by the static methods of this class when called by
the application.

A PrintServiceLookup implementor is recommended to check for the
SecurityManager.checkPrintJobAccess() to deny access to untrusted code.
Following this recommended policy means that untrusted code may not
be able to locate any print services. Downloaded applets are the most
common example of untrusted code.

This check is made on a per lookup service basis to allow flexibility in
the policy to reflect the needs of different lookup services.

Services which are registered by registerService(PrintService)
will not be included in lookup results if a security manager is
installed and its checkPrintJobAccess() method denies access.
/** Implementations of this class provide lookup services for
  * print services (typically equivalent to printers) of a particular type.
  * <p>
  * Multiple implementations may be installed concurrently.
  * All implementations must be able to describe the located printers
  * as instances of a PrintService.
  * Typically implementations of this service class are located
  * automatically in JAR files (see the SPI JAR file specification).
  * These classes must be instantiable using a default constructor.
  * Alternatively applications may explicitly register instances
  * at runtime.
  * <p>
  * Applications use only the static methods of this abstract class.
  * The instance methods are implemented by a service provider in a subclass
  * and the unification of the results from all installed lookup classes
  * are reported by the static methods of this class when called by
  * the application.
  * <p>
  * A PrintServiceLookup implementor is recommended to check for the
  * SecurityManager.checkPrintJobAccess() to deny access to untrusted code.
  * Following this recommended policy means that untrusted code may not
  * be able to locate any print services. Downloaded applets are the most
  * common example of untrusted code.
  * <p>
  * This check is made on a per lookup service basis to allow flexibility in
  * the policy to reflect the needs of different lookup services.
  * <p>
  * Services which are registered by registerService(PrintService)
  * will not be included in lookup results if a security manager is
  * installed and its checkPrintJobAccess() method denies access.
  */

public abstract class PrintServiceLookup {

    static class Services {
        private ArrayList listOfLookupServices = null;
        private ArrayList registeredServices = null;
    }

    private static Services getServicesForContext() {
        Services services =
            (Services)AppContext.getAppContext().get(Services.class);
        if (services == null) {
            services = new Services();
            AppContext.getAppContext().put(Services.class, services);
        }
        return services;
    }

    private static ArrayList getListOfLookupServices() {
        return getServicesForContext().listOfLookupServices;
    }

    private static ArrayList initListOfLookupServices() {
        ArrayList listOfLookupServices = new ArrayList();
        getServicesForContext().listOfLookupServices = listOfLookupServices;
        return listOfLookupServices;
    }


    private static ArrayList getRegisteredServices() {
        return getServicesForContext().registeredServices;
    }

    private static ArrayList initRegisteredServices() {
        ArrayList registeredServices = new ArrayList();
        getServicesForContext().registeredServices = registeredServices;
        return registeredServices;
    }

    
Locates print services capable of printing the specified DocFlavor. 
Params:
flavor – the flavor to print. If null, this constraint is not
       used.
attributes – attributes that the print service must support.
If null this constraint is not used.
Returns:
array of matching PrintService objects
representing print services that support the specified flavor
attributes.  If no services match, the array is zero-length./**
     * Locates print services capable of printing the specified
     * {@link DocFlavor}.
     *
     * @param flavor the flavor to print. If null, this constraint is not
     *        used.
     * @param attributes attributes that the print service must support.
     * If null this constraint is not used.
     *
     * @return array of matching <code>PrintService</code> objects
     * representing print services that support the specified flavor
     * attributes.  If no services match, the array is zero-length.
     */
    public static final PrintService[]
        lookupPrintServices(DocFlavor flavor,
                            AttributeSet attributes) {
        ArrayList list = getServices(flavor, attributes);
        return (PrintService[])(list.toArray(new PrintService[list.size()]));
    }


    
Locates MultiDoc print Services capable of printing MultiDocs
containing all the specified doc flavors.
 This method is useful to help locate a service that can print
a MultiDoc in which the elements may be different
flavors. An application could perform this itself by multiple lookups
on each DocFlavor in turn and collating the results,
but the lookup service may be able to do this more efficiently.
Params:
flavors – the flavors to print. If null or empty this
       constraint is not used.
Otherwise return only multidoc print services that can print all
specified doc flavors.
attributes – attributes that the print service must
support.  If null this constraint is not used.
Returns:
array of matching MultiDocPrintService objects. If no services match, the array is zero-length./**
     * Locates MultiDoc print Services capable of printing MultiDocs
     * containing all the specified doc flavors.
     * <P> This method is useful to help locate a service that can print
     * a <code>MultiDoc</code> in which the elements may be different
     * flavors. An application could perform this itself by multiple lookups
     * on each <code>DocFlavor</code> in turn and collating the results,
     * but the lookup service may be able to do this more efficiently.
     *
     * @param flavors the flavors to print. If null or empty this
     *        constraint is not used.
     * Otherwise return only multidoc print services that can print all
     * specified doc flavors.
     * @param attributes attributes that the print service must
     * support.  If null this constraint is not used.
     *
     * @return array of matching {@link MultiDocPrintService} objects.
     * If no services match, the array is zero-length.
     *
     */
    public static final MultiDocPrintService[]
        lookupMultiDocPrintServices(DocFlavor[] flavors,
                                    AttributeSet attributes) {
        ArrayList list = getMultiDocServices(flavors, attributes);
        return (MultiDocPrintService[])
            list.toArray(new MultiDocPrintService[list.size()]);
    }


    
Locates the default print service for this environment.
This may return null.
If multiple lookup services each specify a default, the
chosen service is not precisely defined, but a
platform native service, rather than an installed service,
is usually returned as the default.  If there is no clearly
identifiable
platform native default print service, the default is the first
to be located in an implementation-dependent manner.

This may include making use of any preferences API that is available
as part of the Java or native platform.
This algorithm may be overridden by a user setting the property
javax.print.defaultPrinter.
A service specified must be discovered to be valid and currently
available to be returned as the default.
Returns:
the default PrintService./**
     * Locates the default print service for this environment.
     * This may return null.
     * If multiple lookup services each specify a default, the
     * chosen service is not precisely defined, but a
     * platform native service, rather than an installed service,
     * is usually returned as the default.  If there is no clearly
     * identifiable
     * platform native default print service, the default is the first
     * to be located in an implementation-dependent manner.
     * <p>
     * This may include making use of any preferences API that is available
     * as part of the Java or native platform.
     * This algorithm may be overridden by a user setting the property
     * javax.print.defaultPrinter.
     * A service specified must be discovered to be valid and currently
     * available to be returned as the default.
     *
     * @return the default PrintService.
     */

    public static final PrintService lookupDefaultPrintService() {

        Iterator psIterator = getAllLookupServices().iterator();
        while (psIterator.hasNext()) {
            try {
                PrintServiceLookup lus = (PrintServiceLookup)psIterator.next();
                PrintService service = lus.getDefaultPrintService();
                if (service != null) {
                    return service;
                }
            } catch (Exception e) {
            }
        }
        return null;
    }


    
Allows an application to explicitly register a class that
implements lookup services. The registration will not persist
across VM invocations.
This is useful if an application needs to make a new service
available that is not part of the installation.
If the lookup service is already registered, or cannot be registered,
the method returns false.

Params:
sp – an implementation of a lookup service.
Returns:
true if the new lookup service is newly
        registered; false otherwise./**
     * Allows an application to explicitly register a class that
     * implements lookup services. The registration will not persist
     * across VM invocations.
     * This is useful if an application needs to make a new service
     * available that is not part of the installation.
     * If the lookup service is already registered, or cannot be registered,
     * the method returns false.
     * <p>
     *
     * @param sp an implementation of a lookup service.
     * @return <code>true</code> if the new lookup service is newly
     *         registered; <code>false</code> otherwise.
     */
    public static boolean registerServiceProvider(PrintServiceLookup sp) {
        synchronized (PrintServiceLookup.class) {
            Iterator psIterator = getAllLookupServices().iterator();
            while (psIterator.hasNext()) {
                try {
                    Object lus = psIterator.next();
                    if (lus.getClass() == sp.getClass()) {
                        return false;
                    }
                } catch (Exception e) {
                }
            }
            getListOfLookupServices().add(sp);
            return true;
        }

    }


    
Allows an application to directly register an instance of a
class which implements a print service.
The lookup operations for this service will be
performed by the PrintServiceLookup class using the attribute
values and classes reported by the service.
This may be less efficient than a lookup
service tuned for that service.
Therefore registering a PrintServiceLookup instance
instead is recommended.
The method returns true if this service is not previously
registered and is now successfully registered.
This method should not be called with StreamPrintService instances.
They will always fail to register and the method will return false.
Params:
service – an implementation of a print service.
Returns:
true if the service is newly
        registered; false otherwise./**
     * Allows an application to directly register an instance of a
     * class which implements a print service.
     * The lookup operations for this service will be
     * performed by the PrintServiceLookup class using the attribute
     * values and classes reported by the service.
     * This may be less efficient than a lookup
     * service tuned for that service.
     * Therefore registering a <code>PrintServiceLookup</code> instance
     * instead is recommended.
     * The method returns true if this service is not previously
     * registered and is now successfully registered.
     * This method should not be called with StreamPrintService instances.
     * They will always fail to register and the method will return false.
     * @param service an implementation of a print service.
     * @return <code>true</code> if the service is newly
     *         registered; <code>false</code> otherwise.
     */

    public static boolean registerService(PrintService service) {
        synchronized (PrintServiceLookup.class) {
            if (service instanceof StreamPrintService) {
                return false;
            }
            ArrayList registeredServices = getRegisteredServices();
            if (registeredServices == null) {
                registeredServices = initRegisteredServices();
            }
            else {
              if (registeredServices.contains(service)) {
                return false;
              }
            }
            registeredServices.add(service);
            return true;
        }
    }


   
Locates services that can be positively confirmed to support
the combination of attributes and DocFlavors specified.
This method is not called directly by applications.

Implemented by a service provider, used by the static methods
of this class.

The results should be the same as obtaining all the PrintServices
and querying each one individually on its support for the
specified attributes and flavors, but the process can be more
efficient by taking advantage of the capabilities of lookup services
for the print services.
Params:
flavor – of document required.  If null it is ignored.
attributes – required to be supported. If null this
constraint is not used.
Returns:
array of matching PrintServices. If no services match, the
array is zero-length./**
    * Locates services that can be positively confirmed to support
    * the combination of attributes and DocFlavors specified.
    * This method is not called directly by applications.
    * <p>
    * Implemented by a service provider, used by the static methods
    * of this class.
    * <p>
    * The results should be the same as obtaining all the PrintServices
    * and querying each one individually on its support for the
    * specified attributes and flavors, but the process can be more
    * efficient by taking advantage of the capabilities of lookup services
    * for the print services.
    *
    * @param flavor of document required.  If null it is ignored.
    * @param attributes required to be supported. If null this
    * constraint is not used.
    * @return array of matching PrintServices. If no services match, the
    * array is zero-length.
    */
    public abstract PrintService[] getPrintServices(DocFlavor flavor,
                                                    AttributeSet attributes);

    
Not called directly by applications.
Implemented by a service provider, used by the static methods
of this class.
Returns:
array of all PrintServices known to this lookup service
class. If none are found, the array is zero-length./**
     * Not called directly by applications.
     * Implemented by a service provider, used by the static methods
     * of this class.
     * @return array of all PrintServices known to this lookup service
     * class. If none are found, the array is zero-length.
     */
    public abstract PrintService[] getPrintServices() ;


   
Not called directly by applications.

Implemented by a service provider, used by the static methods
of this class.

Locates MultiDoc print services which can be positively confirmed
to support the combination of attributes and DocFlavors specified.

Params:
flavors – of documents required. If null or empty it is ignored.
attributes – required to be supported. If null this
constraint is not used.
Returns:
array of matching PrintServices. If no services match, the
array is zero-length./**
    * Not called directly by applications.
    * <p>
    * Implemented by a service provider, used by the static methods
    * of this class.
    * <p>
    * Locates MultiDoc print services which can be positively confirmed
    * to support the combination of attributes and DocFlavors specified.
    * <p>
    *
    * @param flavors of documents required. If null or empty it is ignored.
    * @param attributes required to be supported. If null this
     * constraint is not used.
    * @return array of matching PrintServices. If no services match, the
    * array is zero-length.
    */
    public abstract MultiDocPrintService[]
        getMultiDocPrintServices(DocFlavor[] flavors,
                                 AttributeSet attributes);

    
Not called directly by applications.
Implemented by a service provider, and called by the print lookup
service
Returns:
the default PrintService for this lookup service.
If there is no default, returns null./**
     * Not called directly by applications.
     * Implemented by a service provider, and called by the print lookup
     * service
     * @return the default PrintService for this lookup service.
     * If there is no default, returns null.
     */
    public abstract PrintService getDefaultPrintService();

    private static ArrayList getAllLookupServices() {
        synchronized (PrintServiceLookup.class) {
            ArrayList listOfLookupServices = getListOfLookupServices();
            if (listOfLookupServices != null) {
                return listOfLookupServices;
            } else {
                listOfLookupServices = initListOfLookupServices();
            }
            try {
                java.security.AccessController.doPrivileged(
                     new java.security.PrivilegedExceptionAction() {
                        public Object run() {
                            Iterator<PrintServiceLookup> iterator =
                                ServiceLoader.load(PrintServiceLookup.class).
                                iterator();
                            ArrayList los = getListOfLookupServices();
                            while (iterator.hasNext()) {
                                try {
                                    los.add(iterator.next());
                                }  catch (ServiceConfigurationError err) {
                                    /* In the applet case, we continue */
                                    if (System.getSecurityManager() != null) {
                                        err.printStackTrace();
                                    } else {
                                        throw err;
                                    }
                                }
                            }
                            return null;
                        }
                });
            } catch (java.security.PrivilegedActionException e) {
            }

            return listOfLookupServices;
        }
    }

    private static ArrayList getServices(DocFlavor flavor,
                                         AttributeSet attributes) {

        ArrayList listOfServices = new ArrayList();
        Iterator psIterator = getAllLookupServices().iterator();
        while (psIterator.hasNext()) {
            try {
                PrintServiceLookup lus = (PrintServiceLookup)psIterator.next();
                PrintService[] services=null;
                if (flavor == null && attributes == null) {
                    try {
                    services = lus.getPrintServices();
                    } catch (Throwable tr) {
                    }
                } else {
                    services = lus.getPrintServices(flavor, attributes);
                }
                if (services == null) {
                    continue;
                }
                for (int i=0; i<services.length; i++) {
                    listOfServices.add(services[i]);
                }
            } catch (Exception e) {
            }
        }
        /* add any directly registered services */
        ArrayList registeredServices = null;
        try {
          SecurityManager security = System.getSecurityManager();
          if (security != null) {
            security.checkPrintJobAccess();
          }
          registeredServices = getRegisteredServices();
        } catch (SecurityException se) {
        }
        if (registeredServices != null) {
            PrintService[] services = (PrintService[])
                registeredServices.toArray(
                           new PrintService[registeredServices.size()]);
            for (int i=0; i<services.length; i++) {
                if (!listOfServices.contains(services[i])) {
                    if (flavor == null && attributes == null) {
                        listOfServices.add(services[i]);
                    } else if (((flavor != null &&
                                 services[i].isDocFlavorSupported(flavor)) ||
                                flavor == null) &&
                               null == services[i].getUnsupportedAttributes(
                                                      flavor, attributes)) {
                        listOfServices.add(services[i]);
                    }
                }
            }
        }
        return listOfServices;
    }

    private static ArrayList getMultiDocServices(DocFlavor[] flavors,
                                                 AttributeSet attributes) {


        ArrayList listOfServices = new ArrayList();
        Iterator psIterator = getAllLookupServices().iterator();
        while (psIterator.hasNext()) {
            try {
                PrintServiceLookup lus = (PrintServiceLookup)psIterator.next();
                MultiDocPrintService[] services  =
                    lus.getMultiDocPrintServices(flavors, attributes);
                if (services == null) {
                    continue;
                }
                for (int i=0; i<services.length; i++) {
                    listOfServices.add(services[i]);
                }
            } catch (Exception e) {
            }
        }
        /* add any directly registered services */
        ArrayList registeredServices = null;
        try {
          SecurityManager security = System.getSecurityManager();
          if (security != null) {
            security.checkPrintJobAccess();
          }
          registeredServices = getRegisteredServices();
        } catch (Exception e) {
        }
        if (registeredServices != null) {
            PrintService[] services = (PrintService[])
                registeredServices.toArray(
                           new PrintService[registeredServices.size()]);
            for (int i=0; i<services.length; i++) {
                if (services[i] instanceof MultiDocPrintService &&
                    !listOfServices.contains(services[i])) {
                    if (flavors == null || flavors.length == 0) {
                        listOfServices.add(services[i]);
                    } else {
                        boolean supported = true;
                        for (int f=0; f<flavors.length; f++) {
                            if (services[i].isDocFlavorSupported(flavors[f])) {

                                if (services[i].getUnsupportedAttributes(
                                     flavors[f], attributes) != null) {
                                        supported = false;
                                        break;
                                }
                            } else {
                                supported = false;
                                break;
                            }
                        }
                        if (supported) {
                            listOfServices.add(services[i]);
                        }
                    }
                }
            }
        }
        return listOfServices;
    }

}