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This artifact provides a single jar that contains all classes required to use remote EJB and JMS, including all dependencies. It is intended for use by those not using maven, maven users should just import the EJB and JMS BOM's instead (shaded JAR's cause lots of problems with maven, as it is very easy to inadvertently end up with different versions on classes on the class path).

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/*
 * 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.sshd.common;

import java.util.Objects;
import java.util.function.Function;

/**
 * Provides the capability to attach in-memory attributes to the entity
 *
 * @author Apache MINA SSHD Project
 */
public interface AttributeStore extends AttributeRepository {
    /**
     * If the specified key is not already associated with a value (or is mapped to {@code null}), attempts to compute
     * its value using the given mapping function and enters it into this map unless {@code null}.
     *
     * @param        The generic attribute type
     * @param  key      The key of the attribute; must not be {@code null}.
     * @param  resolver The (never {@code null}) mapping function to use if value not already mapped. If returns
     *                  {@code null} then value is not mapped to the provided key.
     * @return          The resolved value - {@code null} if value not mapped and resolver did not return a
     *                  non-{@code null} value for it
     */
    default  T computeAttributeIfAbsent(
            AttributeKey key, Function, ? extends T> resolver) {
        Objects.requireNonNull(resolver, "No resolver provided");

        T value = getAttribute(key);
        if (value != null) {
            return value;
        }

        value = resolver.apply(key);
        if (value == null) {
            return null;
        }

        setAttribute(key, value);
        return value;
    }

    /**
     * Sets a user-defined attribute.
     *
     * @param     The generic attribute type
     * @param  key   The key of the attribute; must not be {@code null}.
     * @param  value The value of the attribute; must not be {@code null}.
     * @return       The old value of the attribute; {@code null} if it is new.
     */
     T setAttribute(AttributeKey key, T value);

    /**
     * Removes the user-defined attribute
     *
     * @param   The generic attribute type
     * @param  key The key of the attribute; must not be {@code null}.
     * @return     The removed value; {@code null} if no previous value
     */
     T removeAttribute(AttributeKey key);

    /**
     * Removes all currently stored user-defined attributes
     */
    void clearAttributes();
}