org.apache.sshd.common.AttributeRepository Maven / Gradle / Ivy
/*
* 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.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.Map;
import java.util.Objects;
import org.apache.sshd.common.util.MapEntryUtils;
/**
* @author Apache MINA SSHD Project
*/
public interface AttributeRepository {
/**
*
* 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:
*
*
*
*
* 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);
* }
*
*
*
* @param type of value stored in the attribute.
* @author Apache MINA SSHD Project
*/
// CHECKSTYLE:OFF
class AttributeKey {
public AttributeKey() {
super();
}
}
// CHECKSTYLE:ON
/**
* @return Current number of user-defined attributes stored in the repository
*/
int getAttributesCount();
/**
* Returns the value of the user-defined attribute.
*
* @param The generic attribute type
* @param key The key of the attribute; must not be {@code null}.
* @return {@code null} if there is no value associated with the specified key
*/
T getAttribute(AttributeKey key);
/**
* Attempts to resolve the associated value by going up the store's hierarchy (if any)
*
* @param The generic attribute type
* @param key The key of the attribute; must not be {@code null}.
* @return {@code null} if there is no value associated with the specified key either in this repository or any
* of its ancestors (if any available)
*/
default T resolveAttribute(AttributeKey key) {
return getAttribute(key);
}
/**
* @return A {@link Collection} snapshot of all the currently registered attributes in the repository
*/
Collection> attributeKeys();
static AttributeRepository ofKeyValuePair(AttributeKey key, A value) {
Objects.requireNonNull(key, "No key provided");
Objects.requireNonNull(value, "No value provided");
return ofAttributesMap(Collections.singletonMap(key, value));
}
static AttributeRepository ofAttributesMap(Map, ?> attributes) {
return new AttributeRepository() {
@Override
public int getAttributesCount() {
return attributes.size();
}
@Override
@SuppressWarnings("unchecked")
public T getAttribute(AttributeKey key) {
Objects.requireNonNull(key, "No key provided");
return MapEntryUtils.isEmpty(attributes) ? null : (T) attributes.get(key);
}
@Override
public Collection> attributeKeys() {
return MapEntryUtils.isEmpty(attributes)
? Collections.emptySet()
: new HashSet<>(attributes.keySet());
}
@Override
public String toString() {
return AttributeRepository.class.getSimpleName() + "[" + attributes + "]";
}
};
}
}