/*
* 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.flink.streaming.api.functions.windowing;
import org.apache.flink.annotation.PublicEvolving;
import org.apache.flink.api.common.functions.AbstractRichFunction;
import org.apache.flink.api.common.state.KeyedStateStore;
import org.apache.flink.streaming.api.windowing.windows.Window;
import org.apache.flink.util.Collector;
/**
* Base abstract class for functions that are evaluated over non-keyed windows using a context
* for retrieving extra information.
*
* @param <IN> The type of the input value.
* @param <OUT> The type of the output value.
* @param <W> The type of {@code Window} that this window function can be applied on.
*/
@PublicEvolving
public abstract class ProcessAllWindowFunction<IN, OUT, W extends Window> extends AbstractRichFunction {
private static final long serialVersionUID = 1L;
/**
* Evaluates the window and outputs none or several elements.
*
* @param context The context in which the window is being evaluated.
* @param elements The elements in the window being evaluated.
* @param out A collector for emitting elements.
*
* @throws Exception The function may throw exceptions to fail the program and trigger recovery.
*/
public abstract void process(Context context, Iterable<IN> elements, Collector<OUT> out) throws Exception;
/**
* Deletes any state in the {@code Context} when the Window is purged.
*
* @param context The context to which the window is being evaluated
* @throws Exception The function may throw exceptions to fail the program and trigger recovery.
*/
public void clear(Context context) throws Exception {}
/**
* The context holding window metadata.
*/
public abstract class Context {
/**
* @return The window that is being evaluated.
*/
public abstract W window();
/**
* State accessor for per-key and per-window state.
*
* <p><b>NOTE:</b>If you use per-window state you have to ensure that you clean it up
* by implementing {@link ProcessWindowFunction#clear(ProcessWindowFunction.Context)}.
*/
public abstract KeyedStateStore windowState();
/**
* State accessor for per-key global state.
*/
public abstract KeyedStateStore globalState();
}
}