/*
* 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.beam.runners.core;
import java.io.IOException;
/**
* A namespace used for scoping state stored with {@link StateInternals}.
*
* <p>Instances of {@link StateNamespace} are guaranteed to have a {@link Object#hashCode} and
* {@link Object#equals} that uniquely identify the namespace.
*/
public interface StateNamespace {
/**
* Return a {@link String} representation of the key. It is guaranteed that this
* {@link String} will uniquely identify the key.
*
* <p>This will encode the actual namespace as a {@link String}. It is
* preferable to use the {@link StateNamespace} object when possible.
*
* <p>The string produced by the standard implementations will not contain a '+' character. This
* enables adding a '+' between the actual namespace and other information, if needed, to separate
* the two.
*/
String stringKey();
/**
* Append the string representation of this key to the {@link Appendable}.
*/
void appendTo(Appendable sb) throws IOException;
/**
* Return an {@link Object} to use as a key in a cache.
*
* <p>Different namespaces may use the same key in order to be treated as a unit in the cache.
* The {@link Object}'s {@link Object#hashCode} and {@link Object#equals} methods will be used to
* determine equality.
*/
Object getCacheKey();
}