org.apache.flink.runtime.state.UserFacingListState 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.flink.runtime.state;
import org.apache.flink.api.common.state.ListState;
import java.util.Collections;
import java.util.List;
/**
* Simple wrapper list state that exposes empty state properly as an empty list.
*
* @param The type of elements in the list state.
*/
class UserFacingListState implements ListState {
private final ListState originalState;
private final Iterable emptyState = Collections.emptyList();
UserFacingListState(ListState originalState) {
this.originalState = originalState;
}
// ------------------------------------------------------------------------
@Override
public Iterable get() throws Exception {
Iterable original = originalState.get();
return original != null ? original : emptyState;
}
@Override
public void add(T value) throws Exception {
originalState.add(value);
}
@Override
public void clear() {
originalState.clear();
}
@Override
public void update(List values) throws Exception {
originalState.update(values);
}
@Override
public void addAll(List values) throws Exception {
originalState.addAll(values);
}
}