java/16 : java.desktop/javax/print/PrintServiceLookup.java

PrintServiceLookup
https://openjdk.java.net/
GPLv2 + Classpath Exception
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
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 * 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
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 * 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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 *
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package javax.print;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.ServiceConfigurationError;
import java.util.ServiceLoader;

import javax.print.attribute.AttributeSet;

import sun.awt.AppContext;

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
 * {@code 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 {@code PrintServiceLookup} implementor is recommended to check for the
 * {@code 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 {@link #registerService(PrintService)} will
 * not be included in lookup results if a security manager is installed and its
 * {@code checkPrintJobAccess()} method denies access.
 */
public abstract class PrintServiceLookup {

    Constructor for subclasses to call.
/**
     * Constructor for subclasses to call.
     */
    protected PrintServiceLookup() {}

    Contains a lists of services.
/**
     * Contains a lists of services.
     */
    static class Services {

        The list of lookup services.
/**
         * The list of lookup services.
         */
        private ArrayList<PrintServiceLookup> listOfLookupServices = null;

        The list of registered services.
/**
         * The list of registered services.
         */
        private ArrayList<PrintService> registeredServices = null;
    }

    Returns the services from the current appcontext.
Returns: the services/**
     * Returns the services from the current appcontext.
     *
     * @return the services
     */
    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;
    }

    Returns the list of lookup services.
Returns: the list of lookup services/**
     * Returns the list of lookup services.
     *
     * @return the list of lookup services
     */
    private static ArrayList<PrintServiceLookup> getListOfLookupServices() {
        return getServicesForContext().listOfLookupServices;
    }

    Initialize the list of lookup services.
Returns: the list of lookup services/**
     * Initialize the list of lookup services.
     *
     * @return the list of lookup services
     */
    private static ArrayList<PrintServiceLookup> initListOfLookupServices() {
        ArrayList<PrintServiceLookup> listOfLookupServices = new ArrayList<>();
        getServicesForContext().listOfLookupServices = listOfLookupServices;
        return listOfLookupServices;
    }

    Returns the list of registered services.
Returns: the list of registered services/**
     * Returns the list of registered services.
     *
     * @return the list of registered services
     */
    private static ArrayList<PrintService> getRegisteredServices() {
        return getServicesForContext().registeredServices;
    }

    Initialize the list of registered services.
Returns: the list of registered services/**
     * Initialize the list of registered services.
     *
     * @return the list of registered services
     */
    private static ArrayList<PrintService> initRegisteredServices() {
        ArrayList<PrintService> 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 {@code null}, this constraint is
     *         not used.
     * @param  attributes attributes that the print service must support. If
     *         {@code null} this constraint is not used.
     * @return array of matching {@code PrintService} 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<PrintService> list = getServices(flavor, attributes);
        return 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 {@code MultiDoc} print {@code Services} capable of printing
     * {@code MultiDocs} containing all the specified doc flavors.
     * <p>
     * This method is useful to help locate a service that can print a
     * {@code MultiDoc} in which the elements may be different flavors. An
     * application could perform this itself by multiple lookups on each
     * {@code DocFlavor} 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 {@code 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
     *         {@code 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<MultiDocPrintService> list = getMultiDocServices(flavors, attributes);
        return 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
     * {@code 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 {@code javax.print.defaultPrinter}. A service
     * specified must be discovered to be valid and currently available to be
     * returned as the default.
     *
     * @return the default {@code PrintService}
     */
    public static final PrintService lookupDefaultPrintService() {

        Iterator<PrintServiceLookup> psIterator = getAllLookupServices().iterator();
        while (psIterator.hasNext()) {
            try {
                PrintServiceLookup lus = 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 {@code false}.
     *
     * @param  sp an implementation of a lookup service
     * @return {@code true} if the new lookup service is newly registered;
     *         {@code false} otherwise
     */
    public static boolean registerServiceProvider(PrintServiceLookup sp) {
        synchronized (PrintServiceLookup.class) {
            Iterator<PrintServiceLookup> 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 {@code 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} instance instead is recommended. The method
     * returns {@code true} if this service is not previously registered and is
     * now successfully registered. This method should not be called with
     * {@code StreamPrintService} instances. They will always fail to register
     * and the method will return {@code false}.
     *
     * @param  service an implementation of a print service
     * @return {@code true} if the service is newly registered; {@code false}
     *         otherwise
     */
    public static boolean registerService(PrintService service) {
        synchronized (PrintServiceLookup.class) {
            if (service == null || service instanceof StreamPrintService) {
                return false;
            }
            ArrayList<PrintService> 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 {@code 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 {@code 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 {@code null} it is ignored.
     * @param  attributes required to be supported. If {@code null} this
     *         constraint is not used.
     * @return array of matching {@code 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 {@code 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 {@code MultiDoc} print services which can be positively confirmed
     * to support the combination of attributes and {@code DocFlavors}
     * specified.
     *
     * @param  flavors of documents required. If {@code null} or empty it is
     *         ignored.
     * @param  attributes required to be supported. If {@code null} this
     *         constraint is not used.
     * @return array of matching {@code 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 {@code PrintService} for this lookup service. If
     *         there is no default, returns {@code null}.
     */
    public abstract PrintService getDefaultPrintService();

    Returns all lookup services for this environment.
Returns: all lookup services for this environment/**
     * Returns all lookup services for this environment.
     *
     * @return all lookup services for this environment
     */
    private static ArrayList<PrintServiceLookup> getAllLookupServices() {
        synchronized (PrintServiceLookup.class) {
            ArrayList<PrintServiceLookup> listOfLookupServices = getListOfLookupServices();
            if (listOfLookupServices != null) {
                return listOfLookupServices;
            } else {
                listOfLookupServices = initListOfLookupServices();
            }
            try {
                java.security.AccessController.doPrivileged(
                     new java.security.PrivilegedExceptionAction<Object>() {
                        public Object run() {
                            Iterator<PrintServiceLookup> iterator =
                                ServiceLoader.load(PrintServiceLookup.class).
                                iterator();
                            ArrayList<PrintServiceLookup> 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;
        }
    }

    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: list of matching PrintService objects representing print services that support the specified flavor attributes. If no services match, the empty list is returned./**
     * Locates print services capable of printing the specified
     * {@link DocFlavor}.
     *
     * @param  flavor the flavor to print. If {@code null}, this constraint is
     *         not used.
     * @param  attributes attributes that the print service must support. If
     *         {@code null} this constraint is not used.
     * @return list of matching {@code PrintService} objects representing print
     *         services that support the specified flavor attributes. If no
     *         services match, the empty list is returned.
     */
    private static ArrayList<PrintService> getServices(DocFlavor flavor,
                                                       AttributeSet attributes) {

        ArrayList<PrintService> listOfServices = new ArrayList<>();
        Iterator<PrintServiceLookup> psIterator = getAllLookupServices().iterator();
        while (psIterator.hasNext()) {
            try {
                PrintServiceLookup lus = 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<PrintService> registeredServices = null;
        try {
          SecurityManager security = System.getSecurityManager();
          if (security != null) {
            security.checkPrintJobAccess();
          }
          registeredServices = getRegisteredServices();
        } catch (SecurityException se) {
        }
        if (registeredServices != null) {
            PrintService[] services = 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;
    }

    Locates MultiDoc print Services capable of printing MultiDocs containing all the specified doc flavors. 
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: list of matching MultiDocPrintService objects. If no services match, the empty list is returned./**
     * Locates {@code MultiDoc} print {@code Services} capable of printing
     * {@code MultiDocs} containing all the specified doc flavors.
     *
     * @param  flavors the flavors to print. If {@code 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
     *         {@code null} this constraint is not used.
     * @return list of matching {@link MultiDocPrintService} objects. If no
     *         services match, the empty list is returned.
     */
    private static ArrayList<MultiDocPrintService> getMultiDocServices(DocFlavor[] flavors,
                                                                       AttributeSet attributes) {


        ArrayList<MultiDocPrintService> listOfServices = new ArrayList<>();
        Iterator<PrintServiceLookup> psIterator = getAllLookupServices().iterator();
        while (psIterator.hasNext()) {
            try {
                PrintServiceLookup lus = 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<PrintService> registeredServices = null;
        try {
          SecurityManager security = System.getSecurityManager();
          if (security != null) {
            security.checkPrintJobAccess();
          }
          registeredServices = getRegisteredServices();
        } catch (Exception e) {
        }
        if (registeredServices != null) {
            PrintService[] services =
                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((MultiDocPrintService)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((MultiDocPrintService)services[i]);
                        }
                    }
                }
            }
        }
        return listOfServices;
    }
}
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.
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.
Params:	sp – an implementation of a lookup service
Returns:	`true` if the new lookup service is newly registered; `false` otherwise
Params:	service – an implementation of a print service
Returns:	`true` if the service is newly registered; `false` otherwise
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.
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.
/

java/ 16/ java.desktop/javax/print/PrintServiceLookup.java
