| /* |
| * 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 org.apache.sshd.common.channel.Channel; |
| import org.apache.sshd.common.session.Session; |
| import org.apache.sshd.common.util.ValidateUtils; |
| |
| /** |
| * Provides the capability to attach in-memory attributes to the entity |
| * |
| * @author <a href="mailto:dev@mina.apache.org">Apache MINA SSHD Project</a> |
| */ |
| public interface AttributeStore { |
| /** |
| * <P> |
| * Type safe key for storage of user attributes. Typically it is used as a static |
| * variable that is shared between the producer and the consumer. To further |
| * restrict access the setting or getting it from the store one can add static |
| * {@code get/set methods} e.g: |
| * </P> |
| * |
| * <pre> |
| * public static final AttributeKey<MyValue> MY_KEY = new AttributeKey<MyValue>(); |
| * |
| * public static MyValue getMyValue(Session s) { |
| * return s.getAttribute(MY_KEY); |
| * } |
| * |
| * public static void setMyValue(Session s, MyValue value) { |
| * s.setAttribute(MY_KEY, value); |
| * } |
| * </pre> |
| * |
| * @param <T> type of value stored in the attribute. |
| * @author <a href="mailto:dev@mina.apache.org">Apache MINA SSHD Project</a> |
| */ |
| // CHECKSTYLE:OFF |
| class AttributeKey<T> { |
| public AttributeKey() { |
| super(); |
| } |
| } |
| // CHECKSTYLE:ON |
| |
| /** |
| * Returns the value of the user-defined attribute. |
| * |
| * @param <T> The generic attribute type |
| * @param key The key of the attribute; must not be {@code null}. |
| * @return <tt>null</tt> if there is no value associated with the specified key |
| */ |
| <T> T getAttribute(AttributeKey<T> key); |
| |
| /** |
| * Sets a user-defined attribute. |
| * |
| * @param <T> 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> T setAttribute(AttributeKey<T> key, T value); |
| |
| /** |
| * Removes the user-defined attribute |
| * |
| * @param <T> 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> T removeAttribute(AttributeKey<T> key); |
| |
| /** |
| * Attempts to resolve the associated value by going up the store's |
| * hierarchy (if any) |
| * |
| * @param <T> The generic attribute type |
| * @param key The key of the attribute; must not be {@code null}. |
| * @return <tt>null</tt> if there is no value associated with the specified key |
| * @see Utils |
| */ |
| <T> T resolveAttribute(AttributeKey<T> key); |
| |
| /** |
| * A helper class for attribute store related operations |
| * @author <a href="mailto:dev@mina.apache.org">Apache MINA SSHD Project</a> |
| */ |
| // CHECKSTYLE:OFF |
| final class Utils { |
| // CHECKSTYLE:ON |
| private Utils() { |
| throw new UnsupportedOperationException("No instance allowed"); |
| } |
| |
| /** |
| * @param <T> The generic attribute type |
| * @param manager The {@link FactoryManager} - ignored if {@code null} |
| * @param key The attribute key - never {@code null} |
| * @return Associated value - {@code null} if not found |
| */ |
| public static <T> T resolveAttribute(FactoryManager manager, AttributeKey<T> key) { |
| ValidateUtils.checkNotNull(key, "No key"); |
| return (manager == null) ? null : manager.getAttribute(key); |
| } |
| |
| /** |
| * Attempts to use the session's attribute, if not found then tries the factory manager |
| * |
| * @param <T> The generic attribute type |
| * @param session The {@link Session} - ignored if {@code null} |
| * @param key The attribute key - never {@code null} |
| * @return Associated value - {@code null} if not found |
| * @see Session#getFactoryManager() |
| * @see #resolveAttribute(FactoryManager, AttributeKey) |
| */ |
| public static <T> T resolveAttribute(Session session, AttributeKey<T> key) { |
| ValidateUtils.checkNotNull(key, "No key"); |
| if (session == null) { |
| return null; |
| } |
| |
| T value = session.getAttribute(key); |
| return (value != null) ? value : resolveAttribute(session.getFactoryManager(), key); |
| } |
| |
| /** |
| * Attempts to use the channel attribute, if not found then tries the session |
| * |
| * @param <T> The generic attribute type |
| * @param channel The {@link Channel} - ignored if {@code null} |
| * @param key The attribute key - never {@code null} |
| * @return Associated value - {@code null} if not found |
| * @see Session#getFactoryManager() |
| * @see #resolveAttribute(Session, AttributeKey) |
| */ |
| public static <T> T resolveAttribute(Channel channel, AttributeKey<T> key) { |
| ValidateUtils.checkNotNull(key, "No key"); |
| if (channel == null) { |
| return null; |
| } |
| |
| T value = channel.getAttribute(key); |
| return (value != null) ? value : resolveAttribute(channel.getSession(), key); |
| } |
| } |
| } |