modules/servicecontext/src/main/java/org/apache/tamaya/servicecontext/ServiceContext.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.tamaya.servicecontext;

import java.util.List;


/**
 * This class models the component that is managing the lifecycle current the
 * services used by the Configuration API.
 */
public interface ServiceContext {

    /**
     * @return ordinal of the ServiceContext. The one with the highest ordinal will be taken.
     */
    int ordinal();

    /**
     * Access a service singleton via its type.
     * If multiple implementations for the very serviceType exist then
     * the one with the highest {@link javax.annotation.Priority} will be used.
     *
     * @param <T> the type of the service type.
     * @param serviceType the service type.
     * @return The instance to be used, or {@code null}
     * @throws org.apache.tamaya.ConfigException if there are multiple service implementations with the maximum priority.
     */
    <T> T getService(Class<T> serviceType);

    /**
     * Access a list current services, given its type. The bootstrap mechanism should
     * order the instance for precedence, hereby the most significant should be
     * first in order.
     *
     * @param serviceType
     *            the service type.
     * @param <T> the type of the list element returned by this method
     * @return The instance to be used, never {@code null}
     */
     <T> List<T> getServices(Class<T> serviceType);

    /**
     * Checks the given instance for a @Priority annotation. If present the annotation's value s evaluated. If no such
     * annotation is present, a default priority is returned (1);
     * @param o the instance, not null.
     * @return a priority, by default 1.
     */
    int getPriority(Object o);

}