com.google.cloud.dataflow.sdk.util.state.StateNamespace Maven / Gradle / Ivy
Show all versions of google-cloud-dataflow-java-sdk-all Show documentation
/*
* Copyright (C) 2015 Google Inc.
*
* Licensed 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 com.google.cloud.dataflow.sdk.util.state;
import java.io.IOException;
/**
* A namespace used for scoping state stored with {@link StateInternals}.
*
* Instances of {@code StateNamespace} are guaranteed to have a {@link #hashCode} and
* {@link #equals} that uniquely identify the namespace.
*/
public interface StateNamespace {
/**
* Return a {@link String} representation of the key. It is guaranteed that this
* {@code String} will uniquely identify the key.
*
*
This will encode the actual namespace as a {@code String}. It is
* preferable to use the {@code StateNamespace} object when possible.
*
*
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 {@code Object} to use as a key in a cache.
*
*
Different namespaces may use the same key in order to be treated as a unit in the cache.
* The {@code Object}'s {@code hashCode} and {@code equals} methods will be used to determine
* equality.
*/
Object getCacheKey();
}