https://github.com/eclipse-ee4j/jaxrs-api: Jakarta RESTful Web Services API (Eclipse Foundation) 
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 * Copyright (c) 2010, 2017 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

package javax.ws.rs.core;

import java.util.Collections;
import java.util.Map;
import java.util.Set;


Defines the components of an application and supplies additional
meta-data. An application or implementation supplies a concrete
subclass of this abstract class.

 The implementation-created instance of an Application subclass may be injected into resource classes and providers using Context. 


 In case any of the Application subclass methods or it's constructor throws a RuntimeException, the deployment of the application SHOULD be aborted with a failure. 


Author:Paul Sandoz, Marc Hadley, Marek Potociar
Since:1.0
/**
 * Defines the components of an application and supplies additional
 * meta-data. An application or implementation supplies a concrete
 * subclass of this abstract class.
 * <p>
 * The implementation-created instance of an Application subclass may be
 * injected into resource classes and providers using
 * {@link javax.ws.rs.core.Context}.
 * </p>
 * <p>
 * In case any of the {@code Application} subclass methods or it's constructor
 * throws a {@link RuntimeException}, the deployment of the application SHOULD
 * be aborted with a failure.
 * </p>
 *
 * @author Paul Sandoz
 * @author Marc Hadley
 * @author Marek Potociar
 * @since 1.0
 */
public class Application {

    
Get a set of root resource, provider and feature classes. The default life-cycle for resource class instances is per-request. The default life-cycle for providers (registered directly or via a feature) is singleton. 
 Implementations should warn about and ignore classes that do not conform to the requirements of root resource or provider/feature classes. Implementations should warn about and ignore classes for which getSingletons() returns an instance. Implementations MUST NOT modify the returned set. 



The default implementation returns an empty set.



Returns:a set of root resource and provider classes. Returning null is equivalent to returning an empty set.
/**
     * Get a set of root resource, provider and {@link Feature feature} classes.
     *
     * The default life-cycle for resource class instances is per-request. The default
     * life-cycle for providers (registered directly or via a feature) is singleton.
     * <p>
     * Implementations should warn about and ignore classes that do not
     * conform to the requirements of root resource or provider/feature classes.
     * Implementations should warn about and ignore classes for which
     * {@link #getSingletons()} returns an instance. Implementations MUST
     * NOT modify the returned set.
     * </p>
     * <p>
     * The default implementation returns an empty set.
     * </p>
     *
     * @return a set of root resource and provider classes. Returning {@code null}
     *         is equivalent to returning an empty set.
     */
    public Set<Class<?>> getClasses() {
        return Collections.emptySet();
    }

    
Get a set of root resource, provider and feature instances. Fields and properties of returned instances are injected with their declared dependencies (see Context) by the runtime prior to use. 

Implementations should warn about and ignore classes that do not
conform to the requirements of root resource or provider classes.
Implementations should flag an error if the returned set includes
more than one instance of the same class. Implementations MUST
NOT modify the returned set.




The default implementation returns an empty set.



Returns:a set of root resource and provider instances. Returning null is equivalent to returning an empty set.
/**
     * Get a set of root resource, provider and {@link Feature feature} instances.
     *
     * Fields and properties of returned instances are injected with their declared
     * dependencies (see {@link Context}) by the runtime prior to use.
     * <p>
     * Implementations should warn about and ignore classes that do not
     * conform to the requirements of root resource or provider classes.
     * Implementations should flag an error if the returned set includes
     * more than one instance of the same class. Implementations MUST
     * NOT modify the returned set.
     * </p>
     * <p>
     * The default implementation returns an empty set.
     * </p>
     *
     * @return a set of root resource and provider instances. Returning {@code null}
     *         is equivalent to returning an empty set.
     */
    public Set<Object> getSingletons() {
        return Collections.emptySet();
    }

    
Get a map of custom application-wide properties.

 The returned properties are reflected in the application configuration passed to the server-side features or injected into server-side components. 


 The set of returned properties may be further extended or customized at deployment time using container-specific features and deployment descriptors. For example, in a Servlet-based deployment scenario, web application's <context-param> and Servlet <init-param> values may be used to extend or override values of the properties programmatically returned by this method. 



The default implementation returns an empty set.



Returns:a map of custom application-wide properties. Returning null is equivalent to returning an empty set.
Since:2.0
/**
     * Get a map of custom application-wide properties.
     * <p>
     * The returned properties are reflected in the application {@link Configuration configuration}
     * passed to the server-side features or injected into server-side components.
     * </p>
     * <p>
     * The set of returned properties may be further extended or customized at deployment time
     * using container-specific features and deployment descriptors. For example, in a Servlet-based
     * deployment scenario, web application's {@code <context-param>} and Servlet {@code <init-param>}
     * values may be used to extend or override values of the properties programmatically returned
     * by this method.
     * </p>
     * <p>
     * The default implementation returns an empty set.
     * </p>
     *
     * @return a map of custom application-wide properties. Returning {@code null}
     *         is equivalent to returning an empty set.
     * @since 2.0
     */
    public Map<String, Object> getProperties() {
        return Collections.emptyMap();
    }
}